Download SARS: clinical presentation, transmission

Clinical Science (2006) 110, 193–204 (Printed in Great Britain) doi:10.1042/CS20050188
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SARS: clinical presentation, transmission,
pathogenesis and treatment options
Paul K. S. CHAN∗ †, Julian W. TANG∗ and David S. C. HUI†‡
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Department of Microbiology, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong Special Administrative
Region, People’s Republic of China, †Centre for Emerging Infectious Diseases, School of Public Health, Faculty of Medicine,
The Chinese University of Hong Kong, Hong Kong Special Administrative Region, People’s Republic of China, and ‡Department
of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong Special Administrative
Region, People’s Republic of China
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SARS (severe acute respiratory syndrome) appeared as the first emerging infectious disease of
this century. It is fortunate that the culprit virus can be grown without much difficulty from a
commonly used cell line, allowing an unlimited supply of isolates for further molecular studies
and leading to the development of sensitive diagnostic assays. How the virus has successfully
jumped the species barrier is still a mystery. The superspreading events that occurred within
hospital, hotel and high-density housing estate opens a new chapter in the mechanisms and routes
of virus transmission. The old practice of quarantine proved to be still useful in controlling the
global outbreak. Despite all the available sophisticated tests, alertness with early recognition
by healthcare workers and prompt isolation of suspected cases is still the most important step
for containing the spread of the infection. Although the rapidly evolving outbreak did not allow the
conducting of systematic clinical trails to evaluate treatment options, the accumulated experience
on managing SARS patients will improve the clinical outcome should SARS return. Although SARS
led to more than 700 deaths worldwide, the lessons learnt have prepared healthcare systems
worldwide to face future emerging and re-emerging infections.
INTRODUCTION
An outbreak of atypical pneumonia of unknown aetiology occurred in November 2002 in Foshan, Guangdong
Province in southern China [1,2]. The disease spread to
Guangzhou in early 2003. In March 2003, similar outbreaks were noted in Vietnam, Hong Kong and Canada
and subsequently involved more than 30 countries [3–6].
In view of the multiregion involvement and the severity
of the disease, the WHO (World Health Organization)
declared in early March 2003 that a global outbreak
was occurring and set up a network of laboratories to
investigate the cause as well as means to control the
spread of the disease. The disease was officially named
‘severe acute respiratory syndrome’ (SARS). In late
March 2003, a few laboratories independently identified
Key words: coronavirus, inflammation, respiratory infection, severe acute respiratory syndrome (SARS), viral transmission.
Abbreviations: ACE-II, angiotensin-converting enzyme 2; ALT, alanine aminotransferase; ARDS, acute respiratory distress
syndrome; FIPV, feline infectious peritonitis virus; huMab, human monoclonal antibody; IFN, interferon; IL, interleukin; IP10, IFN-γ -inducible protein-10; IVIg, intravenous γ -globulin; LDH, lactate dehydrogenase; LPV/r, 400 mg of lopinavir/100 mg of
ritonavir; MCP-1, monocyte chemoattractant protein-1; MHV, mouse hepatitis virus; NO, nitric oxide; NPPV, non-invasive positive
pressure ventilation; R0 , reproductive number; S protein, spike glycoprotein; SARS, severe acute respiratory syndrome; SARS-CoV,
SARS-associated coronavirus; TGEV, transmissible gastroenteritis virus; TNF-α, tumour necrosis factor-α; WHO, World Health
Organization.
Correspondence: Professor Paul K. S. Chan, Department of Microbiology, The Chinese University of Hong Kong, 1/F Clinical
Science Building, Prince of Wales Hospital, Shatin, New Territories, Hong Kong Special Administration Region, People’s Republic
of China (email [email protected]).
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a previously unrecognized coronavirus as the aetiological agent of SARS. The virus was named SARS-CoV
(SARS-associated coronavirus). The global outbreak
ended in July 2003 with a total of 8098 probable cases
and at least 774 deaths recorded (see http://www.who.
int/csr/sars/country/table2003 09 23/en for a summary
of probable SARS cases with onset of illness from
1 November to 31 July 2003).
THE VIRUS
The family Coronaviridae contains two separate genera:
coronaviruses and toroviruses. Coronaviruses are found
in a wide range of animal species. In humans, coronaviruses are mainly respiratory pathogens, although they
have been occasionally shown to be the cause of some
cases of diarrhoea. Before the SARS epidemic, only two
human coronaviruses had been characterized (HuCoV229E and HuCoV-OC43). Both of these usually cause a
mild upper respiratory tract infection.
Coronaviruses are large lipid-enveloped, positivesense, single-stranded RNA viruses, approx. 30 kb in
length and are the largest RNA viruses known. The virus
codes for several proteins, including an RNA-dependent
RNA polymerase (Pol), a surface spike glycoprotein (S
protein), which attaches the virus to a host cell and
is the target for neutralizing antibodies [8,9], a small
envelope protein (E), a membrane glycoprotein (M) and
a nucleocapsid protein (N) complexed with the viral
RNA. The haemagglutinin esterase (HE) protein is also
coded for in HuCoV-OC43 and some animal coronaviruses, but not in SARS-CoV [10]. There are other
ORFs (open reading frames), whose functions are
being gradually revealed. Coronaviruses have a unique
replication system in that all mRNAs form a nested
set with a common polyadenylated 3 -end, with only
the unique 5 -end fragment being translated into amino
acids [11]. Mutations are common, as for all RNA
viruses, and if two coronaviruses infect the same host cell
simultaneously genetic recombination is possible [12].
However, no evidence of recombination was found from
the SARS-CoV genomes detected during the course of
global outbreak in 2003 [13,14].
Animal and human coronaviruses have been classified
into three different serologically distinct groups based
on their antigenicity [13,14]: Group 1 contains HuCoV229E and porcine [TGEV (transmissible gastroenteritis
virus) and PDEV, (porcine diarrhoea epidemic virus)], feline [FIPV (feline infectious peritonitis virus)] and canine
coronaviruses; Group 2 contains HuCoV-OC43 along
with MHV (mouse hepatitis virus), bovine coronavirus
and haemagglutinating encephalomyelitis virus; and
Group 3 contains avian coronaviruses, including IBV (infectious bronchitis virus) of chickens and turkey coronavirus. SARS-CoV seems to lie in a group of its own,
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based on sequencing studies of its various viral proteins
[13,14].
The receptor for the human coronavirus HuCoV229E has been reported to be human aminopeptidase N
(CD13) [15]. In Group 2, HuCoV-OC43 may use one of
several cell-surface molecules, including 9-O-acetylated
neuraminic acid and the HLA-1 molecules [16,17]. It has
been shown that SARS-CoV uses ACE-II (angiotensinconverting enzyme 2) as the cellular receptor [18,19].
A good correlation between the expression of ACE-II
and tissue tropism has been shown [20]; however, the
presence of ACE-II is unlikely to be the sole determinant
for tropism [21]. The C-type lectin CD209L (L-SIGN)
human cellular glycoprotein may also possibly be a
receptor for SARS-CoV [22].
CLINICAL FEATURES
SARS-CoV produces an acute viral infection in humans
with an incubation period ranging from 2–10 days [3–5].
During the 2003 outbreak, most patients were admitted to
hospital between 3–5 days following the onset of illness
[23]. The presenting features in adults are pronounced.
These include persistent high fever, chills and rigor,
malaise, myalgia, headache and dry cough. Most patients
had some degree of dyspnoea at presentation, which
increased towards the end of the first week of illness.
Sputum production, sore throat and rhinorrhoea were
less commonly reported symptoms [3–5,24,25].
The reported proportion of patients with gastrointestinal symptoms varies among different clusters. For the
first hospital outbreak in Hong Kong, 20 % of patient had
diarrhoea at presentation, and another 18 % developed diarrhoea during the course of illness [26]. It is worth
noting that in eight of the 138 (5.8 %) patients in the
cohort, fever and diarrhoea were their only presenting
symptoms. The diarrhoea was mainly watery without
blood or mucus, lasting for 3.7 +
− 2.7 days. A few patients
had mild abdominal pain. In the Toronto outbreak, 24 %
of the 144 patients had diarrhoea at presentation [5]. A
remarkably high proportion (70 %) of patients in the
rapidly evolving community outbreak, which occurred
at the Amoy Gardens Residential Estate in Hong Kong,
had diarrhoea at presentation.
Reactive hepatitis is a common complication of SARSCoV infection with 24 % of patients having elevated ALT
(alanine aminotransferase) levels on admission, and 69 %
had raised ALT levels during the subsequent course of
their illness. Those with severe hepatitis had worse clinical
outcome [27].
Lymphopenia, low-grade disseminated intravascular
coagulation (DIC-thrombocytopenia, prolonged activated partial thromboplastin time and elevated D-dimers),
elevated LDH (lactate dehydrogenase) and CK (creatinine kinase) are common abnormalities detected in SARS
patients [3–6,28,29].
SARS: clinical presentation, transmission, pathogenesis and treatment options
In general, the radiographical features of SARS are similar to those found in community-acquired pneumonia
caused by other organisms [30]. Nevertheless, several
characteristic features are frequently observed in SARS,
including the predominant involvement of the lung periphery and the lower zones, whereas cavitation, hilar lymphadenopathy and pleural effusion are rarely found
[3,30]. Radiographical changes progress from a unilateral
focal air-space opacity, to multifocal or bilateral involvement during the later phase of disease. These lesions resolve, naturally or as a response to treatment, in a large
proportion of patients (Figure 1) [3,30]. In a case
series, 12 % of patients developed spontaneous pneumomediastinum and 20 % of patients developed evidence
of ARDS (acute respiratory distress syndrome) over a
period of 3 weeks [31]. The reported incidence of barotrauma among patients receiving intensive care was high
(26 %), despite using low-volume and low-pressure
mechanical ventilation [32]. High-resolution computer
tomography of the thorax is useful in detecting lung
opacities in cases with a high index of clinical suspicion
of SARS, but with unrevealing unremarkable chest radiographs. Remarkable features observed from high-resolution computer tomography include ground-glass opacification, sometimes with consolidation, and interlobular
septal and intralobular interstitial thickening, with predominantly peripheral and lower lobe involvement (Figure 2) [33].
SARS-CoV was detected in the cerebrospinal fluid
and serum samples of two cases with status epilepticus
[34,35]. The data suggest that a severe acute neurological
syndrome might occasionally accompany SARS.
Older subjects with SARS often show atypical presenting features such as decrease in general well-being,
poor feeding and delirium [36–38]. The fact that older
SARS patients might be afebrile further hinders early
recognition. Young children (< 12 years of age) often run
a more benign clinical course mimicking other viral upper
respiratory tract infections, whereas teenagers tend to
have a clinical course similar to that of adult SARS patients
[3,39]. No fatality has been reported in young children
and teenage patients [39–42].
A number of studies have been conducted to search
for asymptomatic cases of SARS-CoV infection [43,44].
It is now quite certain that asymptomatic infection is very
rare in adults; however, data on children and elderly are
less comprehensive.
TRANSMISSION
The origin of SARS-CoV is, at present, thought to
be the Himalayan palm civet (Paguma larvata) found
in Guangdong province in south China, from which
coronaviruses very similar to SARS-CoV isolated from
humans have been detected [45–47]. The fact that a much
Figure 1 Serial chest radiographs of a 31-year-old healthcare worker infected with SARS in 2003
There was an opacity involving the right upper lobe initially (a), with progression
to ARDS during the second week of his illness requiring invasive mechanical
ventilation (b). Following intensive care support and treatment with intravenous
pulse of steroids, he made an uneventful recovery (c).
higher seroprevalence of SARS-CoV was found among
wild animal handlers in Guangdong also supports its
animal origin. Although it is still a mystery how SARSCoV has crossed the species barrier, a number of reports
have provided detailed descriptions on the transmission
of SARS-CoV among humans.
The transmission of most respiratory viruses is a
combination of direct contact (touch), short-range (large
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Figure 2 High-resolution computer tomography of the
thorax taken on day 7 of a patient with SARS
Several areas of ground-glass opacities involving predominantly the lower lobes of
both lungs were observed.
droplet; within 1 m) and long-range (droplet nuclei;
beyond 1 m and further) [48,49]. There are several infectious agents that are recognized to be spread by all
three routes with equal importance, e.g. tuberculosis,
measles and chicken pox [49], but most are transmitted
mainly by direct contact and short-range routes, with
occasional instances where long-range transmission can
be the only explanation, e.g. influenza [50]. The source for
such transmission events is normally the infected patient’s
upper respiratory tract, and not via the haematogenous
or faecal–oral routes. The transmission of SARS-CoV
is similar to other respiratory viruses, but with several
important differences. A brief summary of the early stage
of the SARS epidemic in Hong Kong will highlight this.
The first international dissemination of SARS-CoV
was related to a ‘superspreader’, a 64-year-old physician
from southern China. He visited Hong Kong on
21 February 2003 and stayed in Hotel M. He died 10 days
later of severe pneumonia. He spread the infection to at
least 16 hotel guests or visitors who had visited the floor
where he stayed. The infection was spread subsequently
to other parts of Hong Kong, Vietnam, Singapore [4] and
Canada [5] within a short period of time [3–6].
The high infectivity of this viral illness is supported
by the fact that 138 patients (many of whom were healthcare workers) were infected with SARS-CoV within
2 weeks after the admission of this single index case
from Hotel M [3,51]. This superspreading event is
thought to be related to the administration of a nebulized
bronchodilator to the index case, together with overcrowding and poor ventilation in the hospital ward. Many
cases of nosocomial SARS-CoV transmission between
healthcare workers and patients occurred in intensive care
units, where there is particularly close contact between
healthcare workers and patients [52–56].
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Next, there was evidence to suggest that SARS might
have spread by long-range airborne transmission in a
major community outbreak in a private residential complex in Hong Kong [57]. There are several other hypotheses for this major outbreak, including passive carriage
of viruses by pests, drying up of U-shaped bathroom
floor drain which allowed the backflow of contaminated
sewage or its aerosolized particles and creation of infectious aerosol current by the use of residential exhaust
fans in the toilet [58,59]. Other circumstantial evidence
are also in line with the airborne transmission hypothesis
for SARS-CoV. For instances, air samples obtained from
a room occupied by a SARS patient, and swabs taken
from frequently touched surfaces in rooms and at a
nurse station, were positive for SARS-CoV by PCR [60].
The temporal–spatial spread of SARS among patients in
a medical ward where there was a SARS outbreak, at
the Prince of Wales Hospital in Hong Kong, was also
consistent with airborne transmission [61].
Hence, from this account, one of the main difficulties
in controlling SARS transmission during the early stages
of the worldwide epidemic is the readiness with which
the virus could spread between healthcare workers and
their patients (mainly direct or short-range transmission),
but also the existence of ‘superspreaders’ who generate a
far greater than average number of secondary cases. The
reasons for this are still not known for certain, but may
be a combination of host and viral factors.
The basic R0 (reproductive number) of an infectious
agent generally gives an indication of transmissibility
of the agent and can also estimate the vaccine coverage
required in an otherwise susceptible population, to
prevent person-to-person spread of the agent and an
ensuing epidemic. Estimates for the R0 of SARS-CoV
have been reported by several authors, but in each case,
the superspreaders were left out of the estimates, so as
not to skew the results for the majority of SARS-CoVinfected individuals. The R0 for SARS-CoV has been estimated to be between 2 and 3 [62,63]. These two analyses
excluded superspreading events in their final value of
R0 , because the transmission route for these events were
almost certainly atypical of the disease in most cases and
may have been assisted in some way [57,61]. This value
of R0 puts SARS-CoV quite low down on the scale of
transmissibility (Table 1) [64–66]. Thus, in the absence
of superspreaders, the transmissibility of SARS-CoV
would be lower than poliovirus.
PATHOGENESIS
After binding to their respective receptors, using the S
protein, human coronaviruses (HuCoV-229E, HuCoVOC43 and SARS-CoV) enter their host cell. This is
usually a ciliated respiratory tract epithelial cell in the
nasopharynx [12,67]. Thereafter, the mechanisms by
which SARS-CoV causes disease can be separated into
SARS: clinical presentation, transmission, pathogenesis and treatment options
Table 1 R0 for various infectious agents
Adapted from Mims et al. [64], with additional references: ∗ [62,63]; †[65,66].
Infectious disease
Basic R0
Measles
Whooping cough
Mumps
Rubella
Diphtheria
Poliomyelitis
Influenza∗
SARS†
15–17
15–17
10–12
7–8
5–6
5–6
1.68–20
2–3
two: (i) the direct lytic effects of the virus on host cells,
and (ii) the host immune response to the infection.
The immune response to viral invasion and replication
is a combination of early innate and later adaptive
responses. Animal and in vitro studies have demonstrated
that coronavirus replication within the host cell leads to a
variety of effects, such as cellular necrosis or lysis [68,69],
apoptosis [68,70] or cell fusion to form syncytia [71].
Studies in mice have shown that there is a potent CD8
T-cell response with acute MHV infection [72], and that
fulminant hepatitis can result from induced transcription
of a novel fgl2 prothrombinase gene by the MHV
nucleocapsid protein [73]. In cats with FIPV, the humoral
response and production of antibodies to the S protein
induces peritonitis [74].
Human infection with SARS-CoV, similarly, leads to
an acute inflammatory response. In humans, SARS-CoV
causes diffuse alveolar damage and deposition of fibrin
with macrophage and giant cell infiltration in lung tissue
[75,76]. Acute hepatitis has been widely reported and
may be a result of immune-mediated, rather than direct,
SARS-CoV viral damage [27,77,78]. Haematological
disturbances have been suspected to be a result of both
direct viral and immune-mediated mechanisms affecting
haematopoiesis [16]. The S protein may be the main factor
in determining the severity of clinical disease, because of
its roles in viral entry, pathogenesis, antiviral response,
virulence and cellular and species tropism [8,20,45,79].
Again, studies on animal coronavirus S proteins have
helped to define this. Mutations in S proteins have been
shown to significantly affect the viral virulence and tissue
tropism of MHV [80,81] and TGEV [82].
Numerous authors have attempted to determine the
role of various cytokines in the pathogenesis of SARSCoV infection, but the picture is still confusing. Most
reports describe a change in levels of IL (interleukin)-1,
IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13, IL-16, IL17 and IL-18, TNF-α (tumour necrosis factor-α) and
IFN (interferon)-γ and -α, but there is little consistency
between the different reports.
In one study from Hong Kong, 20 patients with
proven SARS-CoV infection demonstrated raised levels
of inflammatory cytokines IL-1, IL-6 and IL-12 and
the neutrophil chemokine IL-8. The Th1 cytokine IFNγ was also raised; however, the inflammatory cytokine
TNF-α was not and neither was the inflammatory cytokine IL-10, the Th1 cytokine IL-2 or the Th2 cytokine
IL-4. The picture is one of Th1-cell-mediated immunity
[83]. Other cytokines shown to be raised were MCP-1
(monocyte chemoattractant protein-1) and IP-10 (IFNγ -inducible protein-10). Other authors have supported
some of these findings. Duan et al. [77] investigated the
cytokine profile in Beijing SARS patients with elevated
liver enzymes and also reported raised levels of IL-1 (IL1β), IL-6 and IL-8, but also raised levels of IL-2, IL-4
and IL-10, in contrast with Wong et al. [83]. In fact,
raised levels of IL-6 and IL-8 have also been reported
from SARS patients in Guangzhou [84] and Taiwan [85].
Xie et al. [86] and Zhang et al. [87] report raised levels of
IL-8 and IL-6 respectively. Some of these studies [77,87]
and others [88] have also reported raised levels of IL-10.
However, contrasting results have also been reported
between these authors. Zhang et al. [87] reported a fall in
IL-8 levels, whereas Wang et al. [89] reported no change
in levels. Similarly, Ng et al. [90] and Wang et al. [89]
reported no change in IL-6 levels. With TNF-α, the
picture is very mixed, with several reports stating an
increase in levels [77,86,89], some reporting no significant
elevation [83,87,90] and others reporting a fall in levels
[85]. The picture for IFN-γ is equally inconsistent with
Wong et al. [83] and Huang et al. [85] reporting a rise in
levels, but Zhang et al. [87] reporting a fall.
The main picture that seems to emerge from the
majority of the studies is that IL-6 and IL-8 are raised
during SARS-CoV infection. IL-6 is secreted by macrophages and T-lymphocytes and causes fever, induces
acute-phase proteins and activates lymphocytes. IL-8
is secreted by monocytes, macrophages, fibroblasts and
keratinocytes and is a chemoattractant and enhances
access for neutrophils to the site of infection [91]. The
reported variations in the levels of all these inflammatory
markers may well be because of differences in sample
collection times relative to the onset of SARS-CoV
infection. Generally, however, the reports agree that
SARS-CoV infection produces a strong host immune
response and that the complications of SARS may well
be a consequence of this. Further studies are necessary to
define the role of specific cytokines better, especially if
they can lead to an earlier diagnosis or prognosis, or even
a specific therapy for SARS [92].
TREATMENT
The clinical course of SARS can be divided into two
phases: Phase I refers to active viral replication where
patients experience high fever, myalgia and other systemic
symptoms that generally improve after a few days; and
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Phase II refers to the stage of immunopathological injury
where patients experience a recurrence of fever, increasing
hypoxaemia and radiological progression of pneumonia
with falls in viral load. The timing of administration of
treatment with respect to these two phases needs to be
considered when evaluating its efficacy.
Ribavirin
Ribavirin, a nucleoside analogue that has activity against
a number of viruses in vitro, was widely used for treating
SARS patients after observing the lack of clinical response
to broad-spectrum antibiotics and oseltamivir [3–6,31].
Nevertheless, it is now known that ribavirin has no
significant in vitro activity against SARS-CoV [93–95].
Haemoglobin levels in approx. 60 % of patients fell by
2 g/dl after 2 weeks of oral ribavirin therapy, at a dose
of 1.2 g three times/day [96]. The use of ribavirin for
SARS in Toronto was based on the higher dosage used
for treating haemorrhagic fever, which led to more toxicity, including elevated liver transaminases and bradycardia [5]. Furthermore, addition of ribavirin did not
have any useful effect on the serum SARS-CoV viral load
in paediatric SARS patients [97]. Therefore it is highly
unlikely that ribavirin alone has any significant clinical
benefits in the treatment of SARS.
Protease inhibitors
Genomic analysis of the SARS-CoV has revealed
several enzymatic targets including proteases [13,14,98].
Lopinavir and ritonavir in combination is a boosted
protease inhibitor regimen widely used in the treatment
of HIV infection. In vitro activity against SARS-CoV has
been demonstrated for lopinavir and ribavirin at 4 and
50 µg/ml respectively. Inhibition of in vitro cytopathic
effects was achieved down to a concentration of 1 µg/ml
lopinavir combined with 6.25 µg/ml ribavirin. The data,
therefore, suggest that this combination might be synergistic against SARS-CoV in vivo [99]. The addition
of LPV/r (400 mg of lopinavir/100 mg of ritonavir) as
initial therapy was associated with significant reduction
in overall death rate (2.3 % compared with 15.6 %) and intubation rate (0 % compared with 11 %) when compared
with a matched historical cohort that received ribavirin
alone as the initial antiviral therapy [100]. Other
reported beneficial effects include a reduction in corticosteroid use, fewer nosocomial infections, a decreasing
viral load and rising peripheral lymphocyte count [99].
In contrast, the subgroup that had received LPV/r as
rescue therapy after receiving pulsed methylprednisolone
treatment for worsening respiratory symptoms was not
better than the matched cohort [100]. The improved
clinical outcome in patients that received LPV/r as part of
the initial therapy may be due to the fact that both peak
(9.6 µg/ml) and trough (5.5 µg/ml) serum concentrations
of lopinavir could inhibit the virus [101]. Nelfinavir,
another protease inhibitor commonly used for HIV
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infection, has been shown to inhibit replication of SARSCoV in Vero cell culture [102]. Further evaluation of this
form of therapy is warranted.
IFNs
Type I IFNs such as IFN-α are produced early as part
of the innate immune response to virus infections. Type I
IFNs inhibit a wide range of RNA and DNA viruses
including SARS CoV in vitro [94,95,103]. Complete
inhibition of cytopathic effects of SARS-CoV in culture
was observed for IFN subtypes β-1b, α-n1 and α-n3, and
human leucocyte IFN-α [94]. IFN-α had an inhibitory
effect in vitro on SARS-CoV starting at concentrations
of 1000 IU/ml (where IU is international units) [95],
whereas recombinant human IFN-β1a potently inhibited
SARS-CoVin vitro [104]. IFN-β and IFN-γ can
synergistically inhibit the replication of SARS-CoV
in vitro [105]. In addition, a combination of ribavirin
and IFN-β has been shown to have synergistic effects
in inhibiting SARS-CoV in animal and human cell lines
[106], and combinations of ribavirin with either IFN-β
1a or IFN-α also show synergistic effects in vitro [107].
In experimentally infected cynomolgus macaques,
prophylactic treatment with pegylated IFN-α significantly reduced viral replication and excretion, viral antigen expression by type 1 pneumocytes and pulmonary
damage compared with untreated macaques, whereas
post-exposure treatment with pegylated IFN-α yielded
intermediate results [108]. Use of IFN-α 1 plus corticosteroids was associated with improved oxygen saturation,
more rapid resolution of radiographical lung opacities
and lower levels of CPK (creatine kinase) in SARS
patients [109]. These findings support clinical testing of
approved IFNs for the treatment of SARS.
huMab (human monoclonal antibody)
There is evidence that SARS-CoV infection is initiated
through binding of the SARS-CoV S protein to ACE-II
[18]. A high-affinity huMab has been identified against
the SARS-CoV S protein, termed 80R, that has potent
neutralizing activity in vitro and in vivo [110]. huMab
80R efficiently neutralizes SARS-CoV and inhibits
syncytia formation between cells expressing the S protein
and those expressing the SARS-CoV receptor ACEII. huMab 80R may be a useful viral entry inhibitor
for the emergency prophylaxis and treatment of SARS
[110]. huMab has been shown to prophylactically reduce
replication of SARS-CoV in the lungs of infected ferrets
and abolish shedding of viruses in pharyngeal secretions
in addition to completely preventing SARS-CoV-induced
macroscopic lung pathology [111].
Vaccines
Currently, different vaccines, such as whole-killed vaccine, adenovirus vector vaccine and recombinant S
SARS: clinical presentation, transmission, pathogenesis and treatment options
protein vaccine, are being tested. An adenoviral-based
vaccine has been shown to induce strong SARS-CoVspecific immune responses in rhesus macaques and hold
promise for the development of a protective vaccine
against SARS-CoV [112]. A DNA vaccine based on the
S gene has been shown to induce the production of a
specific IgG antibody against SARS-CoV efficiently in
mice with a seroconversion rate of 75 % after three doses
of immunization [113,114]. Recombinant S proteins that
exhibit antigenicity and receptor-binding ability are also
good candidates for developing a SARS vaccine [115]. It
have been shown that a recombinant attenuated vaccinia
virus, Ankara, expressing the S protein of SARS-CoV
can elicit protective immunity in mice [116]. Another recombinant attenuated parainfluenza virus expressing the
S protein also produced immunity following intranasal
inoculation to mice [117]. A synthetic peptide derived
from the S protein is another target for vaccine development. Promising results have been obtained in vitro
[118] and in vivo from rabbit and monkey models [119].
Systemic corticosteroids
During the Phase II of clinical course when patients
progressed to develop pneumonia and hypoxaemia, intravenous administration of rescue-pulsed methylprednisolone has been shown to suppress cytokine-induced
lung injury [3,31,96,99,120]. The rationale could be that
the progression of the pulmonary disease is mediated
by the host inflammatory response [31]. Corticosteroids
significantly reduced IL-8, MCP-1 and IP-10 concentrations from 5–8 days after treatment in 20 adult SARS
patients [81]. Induction of IP-10 is thought to be a critical
event in the initiation of immune-mediated lung injury
and lymphocyte apoptosis [82].
The use of rescue-pulsed methylprednisolone during
clinical progression was associated with favourable clinical improvement, with resolution of fever and lung opacities within 2 weeks [3,96,120]. However, a retrospective
analysis showed that the use of pulsed methylprednisolone was associated with increased risk of 30 day
mortality (adjusted odds ratio, 26.0; 95 % confidence
interval, 4.4–154.8) [121]. This retrospective study could
not establish whether a causal relationship existed between the use of methylprednisolone and an increased
risk of death, as clinicians were more inclined to give
pulsed methylprednisolone therapy in deteriorating patients. Nevertheless, complications, such as disseminated
fungal disease [122] and avascular necrosis of bone,
have been reported following prolonged corticosteroid
therapy [123]. With the rescue pulsed steroid approach,
avascular necrosis of bone was found in 12 (4.7 %) patients after screening 254 using MTI (magnetic resonance
imaging). The risk of avascular necrosis was 0.6 %
for patients receiving < 3 g, and was 13 % for those
receiving > 3 g of prednisolone-equivalent dose [124].
A randomized placebo-controlled study conducted at
Prince of Wales Hospital, Hong Kong showed that
plasma SARS-CoV RNA concentrations in the second
and third weeks of illness were higher in patients given
initial hydrocortisone (n = 10) than those given normal
saline (n = 7) during Phase I of the clinical course of
illness [125]. Despite the small sample size, the data
suggest that pulsed steroid given in the earlier phase may
prolong viraemia and thus it should only be given during
later phase for rescue purpose. Carefully designed clinical
trials, if ever possible, of a larger sample size are required
to determine the optimal timing and dosage of systemic
steroid in the treatment of the possibly immune-mediated
lung injury in SARS.
Convalescent plasma
Convalescent plasma, donated by patients who had
recovered from SARS, contains neutralizing antibodies
and may be useful clinically for treating other SARS
patients [126,127]. Research work in the preparation of
SARS-CoV-specific hyperIg from convalescent plasma
donated by patients who have recovered from SARS is
currently in progress.
Traditional Chinese medicine
Glycyrrhizin, an active component of liquorice roots,
has been shown to inhibit the replication of SARS-CoV
in vitro [93]. A controlled study comparing integrative
Chinese and Western medicine compared with Western
medicine alone has suggested that the combination
treatment given in the Phase I of SARS was more effective
in reducing the number of patients with abnormal
oxygen saturation [128]. However, it was not clear which
of the Chinese medicine components was responsible for
the benefit, and the dosage of steroid given to both groups
was not clear.
IVIg (intravenous γ -globulin) and
pentaglobulin
IVIg has immunomodulatory properties and may downregulate cytokine expression [129], and was used quite
extensively in Singapore during the SARS outbreak in
2003. However, it was noted that one-third of critically ill
patients developed venous thromboembolism, including
pulmonary embolism, despite prophylactic use of lowmolecular-mass heparin [54]. There was evidence of
pulmonary embolism in four out of eight postmortem
cases [130]. In addition, there were five cases of large
artery ischaemic stroke of which three cases had been
given IVIg [131].
Pentaglobulin is IgM-enriched Ig. It was administered
to 12 patients with SARS who continued to deteriorate
despite pulsed steroid and ribavirin, and its use was
associated with subsequent improvement in oxygenation
and radiographical scores. It was difficult to judge its
effects, as the study was uncontrolled and pulsed steroid
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2006 The Biochemical Society
199
200
P. K. S. Chan, J. W. Tang and D. S. C. Hui
was also used concurrently [132]. Pulmonary artery
thrombosis has been reported in a patient with SARS who
was treated with ribavirin, steroid, lopinavir/ritonavir,
IVIg and pentaglobulin [133]. It is possible that the IVIgor pentaglobulin-induced increase in viscosity may be
consequential in patients with hypercoagulable states
such as SARS [134].
include advanced age [3,23,31,141], chronic hepatitis B
treated with lamivudine [31], severe hepatitis [27], high
initial LDH [141], high peak LDH [3], high neutrophil
count on presentation [3,141], diabetes mellitus or
other co-morbid conditions [5,142], low CD4 and CD8
lymphocyte counts at presentation [143] and a high
initial SARS-CoV viral load [97,144].
NO (nitric oxide)
Long-term outcome
Inhaled NO has been reported to have beneficial effects
in SARS. In a controlled study comparing the use of
NO (n = 6) and supportive treatment (n = 8) for severe
respiratory failure, there was improvement in oxygenation after inhaled NO was administered and this allowed
ventilatory support to be discontinued. Interestingly,
the beneficial effects persisted after termination of NO
inhalation [135]. NO has been shown to inhibit the
replication cycle of SARS-CoV in vitro [136].
NPPV (non-invasive positive pressure
ventilation)
Approx. 20 % of SARS patients developed ARDS requiring invasive mechanical ventilation and this incurred a
huge demand on intensive care units. Performing endotracheal intubation is a known risk for acquiring SARSCoV from the patient [137]. NPPV via face mask was
applied to 20 patients in a hospital ward in Hong Kong
which was installed with double exhaust fans and full
personal protective equipment. Intubation was avoided
in 14 patients and none of the 105 healthcare workers developed SARS clinically. SARS-CoV serology was negative in 102 (97 %), whereas the other three refused blood
tests [138]. Although one cannot completely eliminate the
possibility of subclinical SARS, it appears that NPPV is
safe when applied in a ward environment with adequate
air exchange provided the healthcare workers are wellequipped with full personal protective equipment and
observe strict contact and droplet precautions [139].
Careful evaluation of the effectiveness of these possible
modalities is needed before they can be recommended for
treatment.
Significant impairment of diffusing capacity occurred
in 15.5 and 23.7 % of SARS survivors at the Prince of
Wales Hospital cohort at 6 and 12 months respectively
[145,146]. Although significant improvement in serial
chest radiography was observed among the SARS survivors, 27.8 % of them still had abnormal radiographical
scores at 12 months [146]. Despite the presence of extensive parenchymal changes revealed by computer
tomography during the early convalescent period, surprisingly most SARS survivors had lung function test
indices within normal limits. However, their exercise
ability (6 min walk distance) at 12 months after illness
onset was remarkably lower than the general population
[146]. The functional disability appears out of proportion to the degree of lung function impairment and may
be due to extrapulmonary factors such as muscle deconditioning and steroid myopathy [145,146]. Critical-illness-associated polyneuropathy/myopathy has also been
observed in a few SARS survivors [147]. The reported
incidence rates of avascular necrosis of bone among
different cohorts in Hong Kong range from 4.7–15 %
[124,148,149], whereas one study from Beijing reported
a high incidence of 42 % [123].
In addition, there was significant impairment of healthrelated quality of life in our patients at 6 and 12 months
[145,146]. The results are not surprising as, in addition
to the physical impairment, the long period of isolation
and extreme uncertainty during the SARS illness had
created enormous psychological stress [150] and mood
disturbances [151]. Furthermore, steroid toxicity, personal vulnerability and psychosocial stressors might have
contributed to the development of psychosis in some
patients [152]. Longer term follow-up is needed to assess
if these deficits are persistent.
OUTCOMES
Short-term outcome
Based on the data received by the WHO (http://www.
who.int/csr/sars/archive/2003 05 07a/en/print.html),
the case fatality rate for SARS was < 1 % for patients
aged 24 years or younger, 6 % for 25–44 years, 15 % for
45–64 years, and > 50 % for patients aged 65 years or
older. There is no evidence to suggest that a difference
in mortality rate exists between different ethnic groups.
A number of clinical/laboratory parameters have been
shown have a prognostic value. Poor prognostic factors
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2006 The Biochemical Society
SUMMARY AND CONCLUSIONS
SARS is a highly infectious disease with a significant
morbidity and mortality. Respiratory failure is the major
complication and 20 % of patients may progress to
ARDS. Healthcare workers are particularly vulnerable
to SARS as the viral load of SARS-CoV in patients increase to peak levels during the second week when
patients are hospitalized [21,31]. Since there is currently
no proven effective treatment for SARS, early recognition, isolation and stringent infection-control measures
SARS: clinical presentation, transmission, pathogenesis and treatment options
are the key to controlling this highly contagious disease.
Isolation facilities, strict droplet and contact precautions
(hand hygiene, gown, gloves, N95 masks and eye protection) for healthcare workers managing SARS patients,
avoid using nebulizers on general wards [3,51], contact
tracing and quarantine isolation for close contacts are
all important measures in controlling the spread of the
infection in hospital and community.
ACKNOWLEDGMENTS
We are grateful to all healthcare workers and research
staff of the Chinese University of Hong Kong for their
dedication to the work on SARS.
REFERENCES
1 Zhao, Z., Zhang, F., Xu, M. et al. (2003) Description and
clinical treatment of an early outbreak of severe acute
respiratory syndrome (SARS) in Guangzhou, PR China.
J. Med. Microbiol. 52, 715–720
2 Xu, R. H., He, J. F., Evans, M. R. et al. (2004)
Epidemiologic clues to SARS origin in China.
Emerg. Infect. Dis. 10, 1030–1037
3 Lee, N., Hui, D. S., Wu, A. et al. (2003) A major outbreak
of severe acute respiratory syndrome in Hong Kong.
N. Engl. J. Med. 348, 1986–1994
4 Hsu, L. Y., Lee, C. C., Green, J. A. et al. (2003) Severe
acute respiratory syndrome in Singapore: Clinical features
of index patient and initial contacts. Emerg. Infect. Dis. 9,
713–717
5 Booth, C. M., Matukas, L. M., Tomlinson, G. A. et al.
(2003) Clinical features and short-term outcomes of
144 patients with SARS in the greater Toronto area.
JAMA, J. Am. Med. Assoc. 289, 2801–2809
6 Tsang, K. W., Ho, P. L., Ooi, G. C. et al. (2003) A cluster
of cases of severe acute respiratory syndrome in
Hong Kong. N. Engl. J. Med. 348, 1977–1985
7 Reference deleted
8 Keng, C. T., Zhang, A., Shen, S. et al. (2005) Amino acids
1055 to 1192 in the S2 region of severe acute respiratory
syndrome coronavirus S protein induce neutralizing
antibodies: implications for the development of vaccines
and antiviral agents. J. Virol. 79, 3289–3296
9 Zhong, X., Yang, H., Guo, Z. F. et al. (2005) B-cell
responses in patients who have recovered from severe
acute respiratory syndrome target a dominant site in the
S2 domain of the surface spike glycoprotein. J. Virol. 79,
3401–3408
10 Xu, J., Hu, J., Wang, J. et al. (2003) Genome organization
of the SARS-CoV. Genomics, Proteomics Bioinformatics
1, 226–235
11 Lai, M. M. and Holmes, K. V. (2001) Coronaviridae: the
viruses and their replication, In Fields Virology, 4th edn
(Knipe, D. M., Howley, P. M., Griffin, D. E. et al., eds.)
pp. 1163–1186, Lippincott Williams & Wilkins,
Philadelphia
12 McIntosh, K. and Andersen, L. J. (2005) Coronaviruses,
including severe acute respiratory syndrome (SARS)associated coronavirus. In Principles and Practice of
Infectious Diseases, 6th edn (Mandell, G. L., Bennett, J. E.
and Dolin, R., eds.), pp. 1990–1997, Churchill
Livingstone, Philadelphia
13 Marra, M. A., Jones, S. J., Astell, C. R., et al. (2003) The
genome sequence of the SARS-associated coronavirus.
Science 300, 1399–1404
14 Rota, P. A., Oberste, M. S., Monroe, S. S. et al. (2003)
Characterization of a novel coronavirus associated with
severe acute respiratory syndrome. Science 300,
1394–1399
15 Yeager, C. L., Ashmun, R. A., Williams, R. K.,
Cardellichio, C. B., Shapiro, L. H., Look, A. T. and
Holmes, K. V. (1992) Human aminopeptidase N is a
receptor for human coronavirus 229E. Nature (London)
357, 420–422
16 Vlasak, R., Luytjes, W., Spaan, W. and Palese, P. (1988)
Human and bovine coronaviruses recognize sialic
acid-containing receptors similar to those of influenza C
viruses. Proc. Natl. Acad. Sci. U.S.A. 85, 4526–4529
17 Collins, A. R. (1994) Human coronavirus OC43 interacts
with major histocompatibility complex class I molecules
at the cell surface to establish infection. Immunol. Invest.
23, 313–321
18 Li, W., Moore, M. J., Vasilieva, N. et al. (2003)
Angiotensin-converting enzyme 2 is a functional receptor
for the SARS coronavirus. Nature (London) 426,
450–454
19 Wang, P., Chen, J., Zheng, A. et al. (2004) Expression
cloning of functional receptor used by SARS coronavirus.
Biochem. Biophys. Res. Commun. 315, 439–444
20 Nie, Y., Wang, P., Shi, X. et al. (2004) Highly infectious
SARS-CoV pseudotyped virus reveals the cell tropism
and its correlation with receptor expression.
Biochem. Biophys. Res. Commun. 321, 994–1000
21 Chan, P. K., To, K. F., Lo, A. W. et al. (2004) Persistent
infection of SARS coronavirus in colonic cells in vitro.
J. Med. Virol. 74, 1–7
22 Jeffers, S. A., Tusell, S. M., Gillim-Ross, L. et al. (2004)
CD209L (L-SIGN) is a receptor for severe acute
respiratory syndrome coronavirus. Proc. Natl. Acad.
Sci. U.S.A. 101, 15748–15753
23 Donnelly, C. A., Ghani, A. V., Leung, G. M. et al. (2003)
Epidemiological determinants of spread of causal agent of
severe acute respiratory syndrome in Hong Kong. Lancet
361, 1761–1766
24 Twu, S. J., Chen, T. J., Chen, C. J. et al. (2003) Control
measures for severe acute respiratory syndrome (SARS)
in Taiwan. Emerg. Infect. Dis. 9, 718–720
25 Hui, D. S., Wong, P. C. and Wang, C. (2003) SARS:
Clinical features and diagnosis. Respirology 8,
S20–S24
26 Leung, W. K., To, K. F., Chan, P. K. et al. (2003) Enteric
involvement of severe acute respiratory syndromeassociated coronavirus infection. Gastroenterology 125,
1011–1017
27 Chan, H. L., Kwan, A. C., To, K. F. et al. (2005) Clinical
significance of hepatic derangement in severe acute
respiratory syndrome. World J. Gastroenterol. 11,
2148–2153
28 Hui, D. S. and Sung, J. J. (2003) Severe acute respiratory
syndrome. Chest 124, 12–15
29 Wong, G. W. and Hui, D. S. (2003) Severe acute
respiratory syndrome: epidemiology, diagnosis and
treatment. Thorax 58, 558–560
30 Wong, K. T., Antonio, G. E., Hui, D. S. et al. (2003)
Severe acute respiratory syndrome: radiographic
appearances and pattern of progression in 138 patients.
Radiology 228, 401–406
31 Peiris, J. S., Chu, C. M., Cheng, V. C. et al. (2003) Clinical
progression and viral load in a community outbreak of
coronavirus-associated SARS pneumonia: a prospective
study. Lancet 361, 1767–1772
32 Gomersall, C. D., Joynt, G. M., Lam, P. et al. (2004)
Short-term outcome of critically ill patients with severe
acute respiratory syndrome. Intensive Care Med. 30,
381–387
33 Wong, K. T., Antonio, G. E., Hui, D. S. et al. (2003) Thin
section CT of Severe Acute Respiratory Syndrome:
evaluation of 73 patients exposed to or with the disease.
Radiology 228, 395–400
34 Hung, E. C., Chim, S. S., Chan, P. K. et al. (2003)
Detection of SARS coronavirus RNA in the cerebrospinal
fluid of a patient with severe acute respiratory syndrome.
Clin. Chem. 49, 2108–2109
35 Lau, K. K., Yu, W. C., Chu, C. M., Lau, S. T., Sheng, B.
and Yuen, K. Y. (2004) Possible central nervous system
infection by SARS coronavirus. Emerg. Infect. Dis. 10,
342–344
C
2006 The Biochemical Society
201
202
P. K. S. Chan, J. W. Tang and D. S. C. Hui
36 Wong, K. C., Leung, K. S. and Hui, M. (2003) Severe
acute respiratory syndrome (SARS) in a geriatric patient
with a hip fracture. A case report. J. Bone Joint Surg. 85A,
1339–1342
37 Tee, A. K., Oh, H. M., Lien, C. T., Narendran, K., Heng,
B. H. and Ling, A. E. (2004) Atypical SARS in a geriatric
patient. Emerg. Infect. Dis. 10, 261–264
38 Fisher, D. A., Lim, T. K., Lim, Y. T., Singh, K. S. and
Tambyah, T. A. (2003) Atypical presentations of SARS.
Lancet 361, 1740
39 Hon, K. L., Leung, C. W., Cheng, W. T. et al. (2003)
Clinical presentations and outcome of severe acute
respiratory syndrome in children. Lancet 561, 1701–1703
40 Sit, S. C., Yau, E. K., Lam, Y. Y. et al. (2003) A young
infant with severe acute respiratory syndrome. Pediatrics
112, e257
41 Bitnun, A., Allen, U., Heurter, H. et al. (2003) Children
hospitalized with severe acute respiratory syndromerelated illness in Toronto. Pediatrics 112, e261
42 Chiu, W. K., Cheung, P. C., Ng, K. L. et al. (2003) Severe
acute respiratory syndrome in children: Experience in a
regional hospital in Hong Kong. Pediatr. Crit. Care Med.
4, 279–283
43 Chan, P. K., Ip, M., Ng, K. C. et al. (2003) Severe acute
respiratory syndrome-associated coronavirus infection.
Emerg. Infect. Dis. 9, 1453–1454
44 Ip, M., Chan, P. K., Lee, N. et al. (2004) Seroprevalence of
antibody to severe acute respiratory syndrome (SARS)associated coronavirus among health care workers in
SARS and non-SARS medical wards. Clin. Infect. Dis. 38,
e116–e118
45 Song, H. D., Tu, C. C., Zhang, G. W. et al. (2005)
Cross-host evolution of severe acute respiratory
syndrome coronavirus in palm civet and human.
Proc. Natl. Acad. Sci. U.S.A. 102, 2430–2435
46 Guan, Y., Zheng, B. J., He, Y. Q. et al. (2003) Isolation and
characterization of viruses related to the SARS
coronavirus from animals in southern China. Science 302,
276–278
47 The Chinese SARS Molecular Epidemiology Consortium
(2004) Molecular evolution of the SARS coronavirus
during the course of the SARS epidemic in China.
Science 303, 1666–1669
48 Aitken, C. and Jeffries, D. J. (2001) Nosocomial spread of
viral disease. Clin. Microbiol. Rev. 14, 528–546
49 Siegel, J., Strausbaugh, L., Jackson, M., Rhinehart, E. and
Chiarello, L. A. (2004) Draft guidelines for isolation
precautions: preventing transmission of infectious agents
in healthcare settings. Recommendations of the
Healthcare Infection Control Practices Advisory
Committee, (http://hica.jp/cdcguideline/
2004DraftIsoGuideline.pdf)
50 Hammond, G. W., Raddatz, R. L. and Gelskey, D. E.
(1989) Impact of atmospheric dispersion and transport
of viral aerosols on the epidemiology of influenza.
Rev. Infect. Dis. 11, 494–497
51 Wong, R. S. and Hui, D. S. (2004) Index patient and SARS
outbreak in Hong Kong. Emerg. Infect. Dis. 10, 339–341
52 Manocha, S., Walley, K. R. and Russell, J. A. (2003) Severe
acute respiratory distress syndrome (SARS): a critical care
perspective. Crit. Care Med. 31, 2684–2692
53 Fowler, R. A., Lapinsky, S. E., Hallett, D. et al. (2003)
Critically ill patients with severe acute respiratory
syndrome. JAMA, J. Am. Med. Assoc. 290, 367–373
54 Lew, T. W., Kwek, T. K., Tai, D. et al. (2003) Acute
respiratory distress syndrome in critically ill patients
with severe acute respiratory syndrome. JAMA, J. Am.
Med. Assoc. 290, 374–380
55 Lapinsky, S. E. and Hawryluck, L. (2003) ICU
management of severe acute respiratory syndrome.
Intensive Care Med. 29, 870–875
56 Tang, J. W. and Chan, R. C. (2004) Severe acute
respiratory syndrome (SARS) in intensive care units
(ICUs): Limiting the risk to healthcare workers.
Curr. Anaesth. Crit. Care 15, 143–155
57 Yu, I. T., Li, Y., Wong, T. W. et al. (2004) Evidence of
airborne transmission of the severe acute respiratory
syndrome virus. N. Engl. J. Med. 350, 1731–1739
C
2006 The Biochemical Society
58 Ng, S. K. (2003) Possible role of an animal vector in the
SARS outbreak at Amoy Gardens. Lancet 362,
570–572
59 Lee, S. H. (2003) The SARS epidemic in Hong Kong.
J. Epidemiol. Community Health 57, 652–654
60 Booth, T. F., Kournikakis, B., Bastien, N. et al. (2005)
Detection of airborne Severe acute respiratory syndrome
(SARS) coronavirus and environmental contamination in
SARS outbreak units. J. Infect. Dis. 191, 1472–1477
61 Yu, I. T., Wong, T. W., Chiu, Y. L., Lee, N. and Li, Y.
(2005) Temporal-spatial analysis of severe acute
respiratory syndrome among hospital inpatients.
Clin. Infect. Dis. 40, 1237–1243
62 Riley, S., Fraser, C., Donnelly, C. A. et al. (2003)
Transmission dynamics of the etiological agent of SARS
in Hong Kong: impact of public health interventions.
Science 300, 1961–1966
63 Lipsitch, M., Cohen, T., Cooper, T. et al. (2003)
Transmission dynamics and control of severe acute
respiratory syndrome. Science 300, 1966–1970
64 Mims, C., Playfair, J., Roitt, I., Wakelin, D. and
Williams, R. (1998) Epidemiologic aspects of the control
of infection and disease. In Medical Microbiology,
2nd edn (Mims, C., Playfair, J., Roitt, I., Wakelin, D. and
Williams, R., eds.), pp. 467–480, Mosby, London
65 Fraser, C., Riley, S., Anderson, R. M. and Ferguson,
N. M. (2004) Factors that make an infectious disease
outbreak controllable. Proc. Natl. Acad. Sci. U.S.A. 101,
6146–6151
66 Mills, C. E., Robins, J. M. and Lipsitch, M. (2004)
Transmissibility of 1918 pandemic influenza.
Nature (London) 432, 904–906
67 Afzelius, B. A. (1994) Ultrastructure of human nasal
epithelium during an episode of coronavirus infection.
Virchows Arch. 424, 295–300
68 Liu, C., Xu, H. Y. and Liu, D. X. (2001) Induction of
caspase-dependent apoptosis in cultured cells by the avian
coronavirus infectious bronchitis Virus. J. Virol. 75,
6402–6409
69 Mossel, E. C., Huang, C., Narayanan, K., Makino, S.,
Tesh, R. B. and Peters, C. J. (2005) Exogenous ACE2
expression allows refractory cell lines to support severe
acute respiratory syndrome coronavirus replication.
J. Virol. 79, 3846–3850
70 Yan, H., Xiao, G., Zhang, J. et al. (2004) SARS
coronavirus induces apoptosis in Vero E6 cells.
J. Med. Virol. 73, 323–331
71 Lavi, E., Wang, Q., Weiss, S. R. and Gonatas, N. K. (1996)
Syncytia formation induced by coronavirus infection is
associated with fragmentation and rearrangement of the
Golgi apparatus. Virology 221, 325–334
72 Marten, N. W., Stohlman, S. A. and Bergmann, C. C.
(2001) MHV infection of the CNS: mechanisms of
immune-mediated control. Viral Immunol. 14, 1–18
73 Ning, Q., Liu, M., Kongkham, P. et al. (1999) The
nucleocapsid protein of murine hepatitis virus type 3
induces transcription of the novel fgl2 prothrombinase
gene. J. Biol. Chem. 274, 9930–9936
74 Weiss, R. C. and Scott, F. W. (1981) Antibody-mediated
enhancement of disease in feline infectious peritonitis:
comparisons with dengue hemorrhagic fever.
Comp. Immunol. Microbiol. Infect. Dis. 4, 175–189
75 Nicholls, J. M., Poon, L. L., Lee, K. C. et al. (2003) Lung
pathology of fatal severe acute respiratory syndrome.
Lancet 361, 1773–1778
76 Antonio, G. E., Wong, K. T., Hui, D. S. et al. (2003)
Thin-section CT in patients with severe acute respiratory
syndrome following hospital discharge: preliminary
experience. Radiology 228, 810–815
77 Duan, Z. P., Chen, Y., Zhang, J., Zhao, J., Lang, Z. W.,
Meng, F. K. and Bao, X. L. (2003) Clinical characteristics
and mechanism of liver injury in patients with severe
acute respiratory syndrome. Zhonghua Ganzangbing
Zazhi 11, 493–496
78 Chan, H. L., Leung, W. K., To, K. F. et al. (2004)
Retrospective analysis of liver function derangement in
severe acute respiratory syndrome. Am. J. Med. 116,
566–567
SARS: clinical presentation, transmission, pathogenesis and treatment options
79 He, Y., Lu, H., Siddiqui, P., Zhou, Y. and Jiang, S. (2005)
Receptor-binding domain of severe acute respiratory
syndrome coronavirus spike protein contains multiple
conformation-dependent epitopes that induce highly
potent neutralizing antibodies. J. Immunol. 174,
4908–4915
80 Sperry, S. M., Kazi, L., Graham, R. L., Baric, R. S., Weiss,
S. R. and Denison, M. R. (2005) Single-amino-acid
substitutions in open reading frame (ORF) 1b-nsp14 and
ORF 2a proteins of the coronavirus mouse hepatitis virus
are attenuating in mice. J. Virol. 79, 3391–3400
81 Leparc-Goffart, I., Hingley, S. T., Chua, M. M.,
Phillips, J., Lavi, E. and Weiss, S. R. (1998) Targeted
recombination within the spike gene of murine
coronavirus mouse hepatitis virus-A59: Q159 is a
determinant of hepatotropism. J. Virol. 72, 9628–9636
82 Ballesteros, M. L., Sanchez, C. M. and Enjuanes, L. (1997)
Two amino acid changes at the N-terminus of
transmissible gastroenteritis coronavirus spike protein
result in the loss of enteric tropism. Virology 227, 378–388
83 Wong, C. K., Lam, C. W., Wu, A. K. et al. (2004) Plasma
inflammatory cytokines and chemokines in severe acute
respiratory syndrome. Clin. Exp. Immunol. 136,
95–103
84 Jiang, Y., Xu, J., Zhou, C. et al. (2005) Characterization of
cytokine/chemokine profiles of severe acute respiratory
syndrome. Am. J. Respir. Crit. Care Med. 171, 850–857
85 Huang, K. J., Su, I. J., Theron, M., Wu, Y. C., Lai, S. K.,
Liu, C. C. and Lei, H. Y. (2005) An interferon-γ -related
cytokine storm in SARS patients. J. Med. Virol. 75,
185–194
86 Xie, J., Han, Y., Li, T. S. et al. (2003) Dynamic changes of
plasma cytokine levels in patients with severe acute
respiratory syndrome. Zhonghua Neike Zazhi 42,
643–645
87 Zhang, Y., Li, J., Zhan, Y. et al. (2004) Analysis of serum
cytokines in patients with severe acute respiratory
syndrome. Infect. Immun. 72, 4410–4415
88 Li, Z., Guo, X., Hao, W. et al. (2003) The relationship
between serum interleukins and T-lymphocyte subsets
in patients with severe acute respiratory syndrome.
Chin. Med. J. (Engl). 116, 981–984
89 Wang, C., Pang, B. S. and National Research Project for
SARS, Beijing Group (2003) Dynamic changes and the
meanings of blood cytokines in severe acute respiratory
syndrome. Zhonghua Jiehe He Huxi Zazhi 26,
586–589
90 Ng, P. C., Lam, C. W., Li, A. M. et al. (2004)
Inflammatory cytokine profile in children with severe
acute respiratory syndrome. Pediatrics 113, e7–e14
91 Lydyard, P. M., Whelan, A. and Fanger, M. W (2004)
Molecules of the innate immune system. Instant Notes in
Immunology, 2nd edn, pp. 23–32, BIOS Scientific
Publishers, New York
92 Openshaw, P. J. (2004) What does the peripheral blood
tell you in SARS? Clin. Exp. Immunol. 136, 11–12
93 Cinatl, J., Morgenstern, B., Bauer, G., Chandra, P.,
Rabenau, H. and Doerr, H. W. (2003) Glycyrrhizin, an
active component of liquorice roots, and replication of
SARS-associated coronavirus. Lancet 361, 2045–2046
94 Tan, E. L., Ooi, E. E., Lin, C. Y., Tan, H. C., Ling, A. E.,
Lim, B. and Stanton, L. W. (2004) Inhibition of SARS
coronavirus infection in vitro with clinically approved
antiviral drugs. Emerg. Infect. Dis. 10, 581–586
95 Stroher, U., DiCaro, A., Li, Y. et al. (2004) Severe acute
respiratory syndrome-related coronavirus is inhibited by
interferon-α. J. Infect. Dis. 189, 1164–1167
96 Sung, J. J., Wu, A., Joynt, G. M. et al. (2004) Severe Acute
Respiratory Syndrome: report of treatment and outcome
after a major outbreak. Thorax 59, 414–420
97 Ng, E. K., Ng, P. C., Hon, K. L. et al. (2003) Serial
analysis of the plasma concentration of SARS coronavirus
RNA in pediatric patients with severe acute respiratory
syndrome. Clin. Chem. 49, 2085–2088
98 Anand, K., Ziebuhr, J., Wadhwani, P., Mesters, J. R. and
Hilgenfeld, R. (2003) Coronavirus main proteinase
(3Clpro) structure: basis for design of anti-SARS drugs.
Science 300, 1763–1767
99 Chu, C. M., Cheng, V. C., Hung, I. F. et al. (2004) Role of
lopinavir/ritonavir in the treatment of SARS: initial
virological and clinical findings. Thorax 59, 252–256
100 Chan, K. S., Lai, S. T., Chu, C. M. et al. (2003) Treatment
of severe acute respiratory syndrome with
lopinavir/ritonavir: a multicenter retrospective matched
cohort study. Hong Kong Med. J. 9, 399–406
101 Hurst, M. and Faulds, D. (2000) Lopinavir. Drugs 60,
1371–1381
102 Yamamoto, N., Yang, R., Yoshinaka, Y. et al. (2004) HIV
protease inhibitor nelfinavir inhibits replication of
SARS-associated coronavirus. Biochem. Biophys.
Res. Commun. 318, 719–725
103 Cinatl, J., Morgenstern, B., Bauer, G., Chandra, P.,
Rabenau, H. and Doerr, H. W. (2003) Treatment of SARS
with human interferons. Lancet 362, 293–294
104 Hensley, L. E., Fritz, L. E., Jahrling, P. B., Karp, C. L.,
Huggins, J. W. and Geisbert, T. W. (2004) Interferon-β1a
and SARS coronavirus replication. Emerg. Infect. Dis. 10,
317–319
105 Sainz, Jr, B., Mossel, E. C., Peters, C. J. and Garry, R. F.
(2004) Interferon-β and interferon-γ synergistically
inhibit the replication of severe acute respiratory
syndrome-associated coronavirus (SARS-CoV). Virology
329, 11–17
106 Morgenstern, B., Michaelis, M., Baer, P. C., Doerr, H. W.
and Cinatl, Jr, J. (2005) Ribavirin and interferon-beta
synergistically inhibit SARS-associated coronavirus
replication in animal and human cell lines.
Biochem. Biophys. Res. Commun. 326, 905–908
107 Chen, F., Chan, K. H., Jiang, Y. et al. (2005) In vitro
susceptibility of 10 clinical isolates of SARS coronavirus
to selected antiviral compounds. J. Clin. Virol. 39, 69–75
108 Haagmans, B. L., Kuiken, T., Martina, B. E. et al. (2004)
Pegylated interferon-α protects type 1 pneumocytes
against SARS coronavirus infection in macaques.
Nat. Med. 10, 290–293
109 Loutfy, M. R., Blatt, L. M., Siminovitch, K. A. et al. (2003)
Interferon Alfacon-1 plus corticosteroids in severe acute
respiratory syndrome: a preliminary study. JAMA, J. Am.
Med. Assoc. 290, 3222–3228
110 Sui, J., Li, W., Murakami, A. et al. (2004) Potent
neutralization of severe acute respiratory syndrome
(SARS) coronavirus by a human mAb to S1 protein that
blocks receptor association. Proc. Natl. Acad. Sci. U.S.A.
101, 2536–2541
111 ter Meulen, J., Bakker, A. B., van den Brink, E. N. et al.
(2004) Human monoclonal antibody as prophylaxis for
SARS coronavirus infection in ferrets. Lancet 363,
2139–2141
112 Gao, W., Tamin, A., Soloff, A. et al. (2003) Effects of a
SARS-associated coronavirus vaccine in monkeys. Lancet
362, 1895–1896
113 Zhao, P., Ke, J. S., Qin, Z. L. et al. (2004) DNA vaccine of
SARS-CoV S gene induces antibody response in mice.
Acta Biochim. Biophys. Sin. (Shanghai) 36, 37–41
114 Yang, Z. Y., Kong, W. P., Huang, Y. et al. (2004) A DNA
vaccine induces SARS coronavirus neutralization and
protective immunity in mice. Nature (London) 428,
561–564
115 Ho, T. Y., Wu, S. L., Cheng, S. E., Wei, Y. C., Huang, S. P.
and Hsiang, C. Y. (2004) Antigenicity and receptorbinding ability of recombinant SARS coronavirus spike
protein. Biochem. Biophys. Res. Commun. 313, 938–947
116 Bisht, H., Roberts, A., Vogel, L. et al. (2004) Severe acute
respiratory syndrome coronavirus spike protein expressed
by attenuated vaccinia virus protectively immunizes mice.
Proc. Natl. Acad. Sci. U.S.A. 101, 6641–6646
117 Bukreyev, A., Lamirande, E. W., Buchholz, U. J. et al.
(2004) Mucosal immunisation of African green monkeys
(Cercopithecus aethiops) with an attenuated parainfluenza
virus expressing the SARS coronavirus spike protein for
the prevention of SARS. Lancet 363, 2122–2127
118 Bosch, B. J., Martina, B. E., van der Zee, R. et al. (2004)
Severe acute respiratory syndrome coronavirus
(SARS-CoV) infection inhibition using spike protein
heptad repeat-derived peptides. Proc. Natl. Acad.
Sci. U.S.A. 101, 8455–8460
C
2006 The Biochemical Society
203
204
P. K. S. Chan, J. W. Tang and D. S. C. Hui
119 Choy, W. Y., Lin, S. G., Chan, P. K. et al. (2004) Synthetic
peptide studies on the severe acute respiratory syndrome
(SARS) coronavirus spike glycoprotein: perspective for
SARS vaccine development. Clin. Chem. 50, 1036–1042
120 Ho, J. C., Ooi, G. C., Mok, T. Y. et al. (2003) High dose
pulse versus non-pulse corticosteroid regimens in
severe acute respiratory syndrome. Am. J. Respir. Crit.
Care Med. 168, 1449–1456
121 Tsang, O. T., Chau, T. N., Choi, K. W. et al. (2003)
Coronavirus-positive nasopharyngeal aspirate as
predictor for severe acute respiratory syndrome mortality.
Emerg. Infect. Dis. 9, 1381–1387
122 Wang, H., Ding, Y., Li, X., Yang, L., Zhang, W. and
Kang, W. (2003) Fatal aspergillosis in a patient with SARS
who was treated with corticosteroids. N. Engl. J. Med.
349, 507–508
123 Hong, N. and Du, X. K. (2004) Avascular necrosis of
bone in severe acute respiratory syndrome. Clin. Radiol.
59, 602–608
124 Griffith, J. F., Antonio, G. E., Kumta, S. M. et al. (2005)
Osteonecrosis of hip and knee in patients with severe
acute respiratory syndrome treated with steroids.
Radiology 235, 168–175
125 Lee, N., Allen Chan, K. C., Hui, D. S. et al. (2004) Effects
of early corticosteroid treatment on plasma SARSassociated Coronavirus RNA concentrations in adult
patients. J. Clin. Virol. 31, 304–309
126 Cheng, Y., Wong, R., Soo, Y. O. et al. (2005) Use of
convalescent plasma therapy in SARS patients in Hong
Kong. Eur. J. Clin. Microbiol. Infect. Dis. 24, 44–46
127 Soo, Y. O., Cheng, Y., Wong, R. et al. (2004)
Retrospective comparison of convalescent plasma with
continuing high-dose methylprednisolone treatment in
SARS patients. Clin. Microbiol. Infect. 10, 676–678
128 Liu, B. Y., Hu, J. Q., Xie, Y. M. et al. (2004) Effects of
integrative Chinese and Western medicine on arterial
oxygen saturation in patients with severe acute respiratory
syndrome. Chin. J. Integrative Med. 10, 117–122
129 Ballow, M. (1997) Mechanisms of action of intravenous
immune serum globulin in autoimmune and inflammatory
diseases. J. Allergy Clin. Immunol. 100, 151–157
130 Chong, P. Y., Chui, P., Ling, A. E. et al. (2004) Analysis of
deaths during the severe acute respiratory syndrome
(SARS) epidemic in Singapore: challenges in determining
a SARS diagnosis. Arch. Pathol. Lab. Med. 128,
195–204
131 Umapathi, T., Kor, A. C., Venketasubramanian, N. et al.
(2004) Large artery ischaemic stroke in severe acute
respiratory syndrome (SARS). J. Neurol. 251, 1227–1231
132 Ho, J. C., Wu, A. Y., Lam, B. et al. (2004) Pentaglobin in
steroid-resistant severe acute respiratory syndrome. Int. J.
Tuberc. Lung Dis. 8, 1173–1179
133 Ng, K. H., Wu, A. K., Cheng, V. C. et al. (2005)
Pulmonary artery thrombosis in a patient with severe
acute respiratory syndrome. Postgrad. Med. J. 81, e3
134 Dalakas, M. C. and Clark, W. M. (2003) Strokes,
thromboembolic events, and IVIg: rare incidents blemish
an excellent safety record. Neurology 60, 1763–1767
135 Chen, L., Liu, P., Gao, H. et al. (2004) Inhalation of nitric
oxide in the treatment of severe acute respiratory
syndrome: a rescue trial in Beijing. Clin. Infect. Dis. 39,
1531–1535
136 Akerstrom, S., Mousavi-Jazi, M., Klingstrom, J.,
Leijon, M., Lunddvist, A. and Mirazimi, A. (2005)
Nitric oxide inhibits the replication cycle of severe
acute respiratory syndrome coronavirus. J. Virol. 79,
1966–1969
137 Fowler, R. A., Guest, C. B., Lapinsky, S. E. et al. (2004)
Transmission of severe acute respiratory syndrome during
intubation and mechanical ventilation. Am. J. Respir. Crit.
Care Med. 169, 1198–1202
138 Cheung, T. M., Yam, L. Y., So, L. K. et al. (2004)
Effectiveness of noninvasive positive pressure ventilation
in the treatment of acute respiratory failure in severe acute
respiratory syndrome. Chest 126, 845–850
139 Hui, D. S. and Sung, J. J. (2004) Treatment of Severe acute
respiratory syndrome. Chest 126, 670–674
140 Reference deleted
141 Tsui, P. T., Kwok, M. L., Yuen, H. and Lai, S. T. (2003)
Severe acute respiratory syndrome: clinical outcome
and prognostic correlates. Emerg. Infect. Dis. 9,
1064–1069
142 Chan, J. W., Ng, C. K., Chan, Y. H. et al. (2003) Short
term outcome and risk factors for adverse clinical
outcomes in adults with severe acute respiratory
syndrome (SARS). Thorax 58, 686–689
143 Wong, R. S., Wu, A., To, K. F. et al. (2003)
Haematological manifestations in patients with severe
acute respiratory syndrome: retrospective analysis.
Br. Med. J. 326, 1358–1362
144 Chu, C. M., Poon, L. L., Cheng, V. C. et al. (2004) Initial
viral load and the outcomes of SARS. Can. Med. Assoc. J.
171, 1349–1352
145 Hui, D. S., Joynt, G. M., Wong, K. T. et al. (2005) Impact
of severe acute respiratory syndrome (SARS) on
pulmonary function, functional capacity and quality of
life in a cohort of survivors. Thorax 60, 401–409
146 Hui, D. S., Wong, K. T., Ko, F. W. et al. (2005) The
one-year impact of severe acute respiratory syndrome
(SARS) on pulmonary function, exercise capacity and
quality of life in a cohort of survivors. Chest 128,
2247–2261
147 Tsai, L. K., Hsieh, S. T., Chao, C. C. et al. (2004)
Neuromuscular disorders in severe acute respiratory
syndrome. Arch. Neurol. 61, 1669–1673
148 Yu, W. C., Hui, D. S. and Chan-Yeung, M. (2004)
Antiviral agents and corticosteroids in the treatment of
SARS. Thorax 59, 643–645
149 Tsang, K. W., Ooi, G. C. and Ho, P. L. (2004) Diagnosis
and pharmacotherapy of severe acute respiratory
syndrome: what have we learnt? Eur. Respir. J. 24,
1025–1032
150 Chua, S. E., Cheung, V., McAlonan, G. M. et al. (2004)
Stress and psychological impact on SARS patients during
the outbreak. Can. J. Psychiatry 49, 385–390
151 Cheng, S. K., Wong, C. W., Tsang, J. and Wong, K. C.
(2004) Psychological distress and negative appraisals in
survivors of severe acute respiratory syndrome (SARS).
Psychol. Med. 34, 1187–1195
152 Lee, D. T., Wing, Y. K., Leung, H. C. et al. (2004) Factors
associated with psychosis among patients with severe
acute respiratory syndrome: a case-control study.
Clin. Infect. Dis. 39, 1247–1249
Received 13 June 2005/21 June 2005; accepted 4 July 2005
Published on the Internet 17 January 2006, doi:10.1042/CS20050188
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2006 The Biochemical Society