Download Respiratory viruses

Respiratory
viruses
1
Categories of Respiratory Viruses
• Orthomyxoviridae: Influenza virus
• Paramyxoviridae : Parainfluenza virus; Mumps
virus; Measles; Respiratory syneytical virus
• Togaviridae: Rubella Virus
• Coronaviridae: Corona Virus; SARS virus
• Adenoviridae : human Adenovirus
• picornaviridae: Rhino Virus;
• Reoviridae:
2
Influenza virus
Orthomyxoviridae: Influenza virus
Influenza is a disease caused by
Influenza virus ,a member of the
Orthomyxoviridae.
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Genome of Influenza virus
• 8 negative sense RNA nucleocapsid
segments
• The 'RNP' (RNA + nucleoprotein) is in a
helical form with the 3 polymerase
polypeptides associated with each segment.
• The segmented genome promotes genetic
diversity caused by mutation and
reassortment of segments on infection
with two different strains
4
Virion
• spherical/ovoid, 80120nm diameter,
• The inner side of
the envelope is
lined by the matrix
protein, stable typespecific.
5
Virion
• The outer surface of the particle consists
of a lipid envelope from which project
prominent glycoprotein spikes of two
types, the haemagglutinin, ~135Å trimer
(HA), and neuraminidase, ~60Å tetramer
(NA).
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Haemagglutinin (HA)
• Encoded by RNA segment #4
• Can agglutinate red blood cells - hence the
nomenclature
• Cleavage by host-cell protease is required (resulting
in HA1 and HA2) for infection to occur
• Hemagglutinin glycoprotein is the viral
attachment protein and fusion protein , and it
elicits neutralizing , protective antibody
responses
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Neuraminadase (NA)
• Encoded by RNA segment #6
• Enzyme that uses neuraminic (sialic) acid as
a substrate
• Important in releasing mature virus from
cells
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ORTHOMYXOVIRUSES
HA - hemagglutinin
NA - neuraminidase
helical nucleocapsid (RNA plus
NP protein)
lipid bilayer membrane
polymerase complex
M1 protein
type A, B, C : NP, M1 protein
sub-types: HA or NA protein
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Influenza virus A
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Replication
• Influenza transcribe and replicates its
genome in the target cell nucleus
• assemble and buds from the plasma
membrane
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Influenza virus
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Antigen
• Soluble antigens: include ribonucleoprotein and
M protein which are much stable in antigenicity.
• Surface antigens: include HA and NA which are
much variable in antigenicity.
13
Types
• Influenza viruses are divided into 3 groups
determined by the ribonucleoprotein (RNP)
antigen and M antigen:
• Group A - This group is the cause of
epidemics and pandemics and has an avian
intermediate host (IH)
Group B - This group causes epidemics and
has no IH
Group C - This group does not cause
epidemics and causes mild disease
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severity of illness
animal reservoir
human pandemics
human epidemics
antigenic changes
segmented genome
amantadine, rimantidine
zanamivir
surface glycoproteins
TYPE A
TYPE B
TYPE C
++++
yes
yes
yes
shift, drift
yes
sensitive
sensitive
2
++
no
no
yes
drift
yes
no effect
sensitive
2
+
no
no
no (sporadic)
drift
yes
no effect
(1)
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Subtypes
• According to antigenicity of HA and NA,
influenza virus is divided into subtypes such as
HnNm( H1N2, et al )
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Variation and Epidemiology
Antigenic drift: median or small epidemic.
Antigenic shift:large scale epidemic.
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Antigenic Shift Of Influenza virus
• Reassortment of genes is a
common feature of Influenza A,
but not B or C
• When two different "A" viruses
infect the same cell, their RNA
segments can become mixed
during replication
• New viruses produced in this way
may survive due to a selective
advantage within the population
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Antigenic Drift of Influenza Virus
• Constant mutations in the RNA of influenza
which lead to polypeptide mutations
• Changes are less dramatic than those induced
by Shift
• If these mutations affect HA or NA they may
cause localized epidemics
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Epidemic
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where do “new” HA and NA come
from?
• 13 types HA
• 9 types NA
– all circulate in birds
• pigs
– avian and human
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where do “new” HA and NA come
from?
23
why do we not have influenza B
pandemics?
• so far no shifts
have been
recorded
• no animal
reservoir known
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Resistence
• The particles are relative labile ,not resistant
to drying, etc.
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Pathogenesis
• Influenza is characterised by fever, myalgia,
headache and pharyngitis. In addition there
may be cough and in severe cases,
prostration. There is usually not coryza鼻炎
(runny nose) which characterises common
cold infections.
• Infection may be very mild, even
asymptomatic, moderate or very severe
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Transmission
• Source of infection: patients and
carriers.
• AEROSOL
– 100,000 TO 1,000,000 VIRIONS
PER DROPLET
• 18-72 HR INCUBATION
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Aerosol
Inoculation
Of virus
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NORMAL TRACHEAL MUCOSA
3 DAYS POST-INFECTION
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7 DAYS POST-INFECTION
SYMPTOMS
•
•
•
•
•
•
FEVER
HEADACHE
MYALGIA(肌痛)
COUGH
RHINITIS(鼻炎)
OCULAR SYMPTOMS
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PULMONARY COMPLICATIONS
• CROUP (YOUNG CHILDREN)
• PRIMARY INFLUENZA VIRUS PNEUMONIA
• SECONDARY BACTERIAL INFECTION
– Streptococcus pneumoniae
– Staphlyococcus aureus
– Hemophilus influenzae
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NON-PULMONARY COMPLICATIONS
• myositis (rare, > in children, > with
type B)
• cardiac complications
• liver and CNS
– Reye’s syndrome
• peripheral nervous system
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Immunity
34
Lab Diagnosis
• Viral detection:
Respiratory secretions
( direct aspirate , gargle , nasal washings )
1. Cell culture in primary monkey kidney or
madindarby canine kidney cells
2. Hemagglutination (inhibition)
Hemadsorption (inhibition)
3. IFA/ ELISA
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• Serology
hemagglutination inhibition
Hemadsorption inhibition
ELISA
immunofluoresence
complement fixation.
NT.
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Prevention
• Vaccines at best give about 70% protection.
They may sometimes not be effective against
the most recently evolved strains because the
rate of evolution outpaces the rate at which
new vaccines can be manufactured.
• This constant antigenic change down the
years means that new vaccines have to be
made on a regular basis.
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Types of Vaccine
• Killed Whole Virus
Rather pyrogenic, not used today.
• Live Virus
Attenuated strains were widely used in Russia but not
elsewhere.
• Virus Subunit
HA extracted from recombinant virus forms the basis of
today's vaccines.
For example, the WHO Recommendation for Influenza
Vaccine, 1995-1996, contains two A strains and one B
strain:-[A / Singapore / 6 / 86 (H1N1)+A / Johannesburg / 33 / 94 (H3N2)
+B / Beijing / 84 / 93 ]
• Synthetic
Much research is being done to try and find a neutralising
epitope that is more stable, and can therefore be used for a
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universal vaccine.
CDC
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PB2
PB1
PA
HA
NA
NP
M
NS
Attenuated Donor
Master Strain
Attenuated Vaccine Strain:
Coat of Virulent strain with
Virulence Characteristics of
Attenuated Strain
X
PB2
PB1
PA
HA
NA
NP
M
NS
PB2
PB1
PA
HA
NA
NP
M
NS
New Virulent
Antigenic Variant
Strain
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Treatment
• Amantadine and rimantadine are active against
influenza A viruses. The action of these closely
related agents is complex and incompletely
understood, but they are believed to block
cellular membrane ion channels, and inhibit an
uncoating step and target the M2 membrane
protein
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PREVENTION - DRUGS
• RIMANTADINE金刚乙胺
(M2)
• type A only
• AMANTADINE金刚烷胺
(M2)
• type A only
• ZANAMIVIR
(NA)
• types A and B, not yet approved for prevention but
studies show effective
• OSELTAMIVIR
(NA)
• types A and B
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TREATMENT - DRUGS
• RIMANTADINE
(M2)
• type A only, needs to be given early
• AMANTADINE
(M2)
• type A only, needs to be given early
• ZANAMIVIR
(NA)
• types A and B, needs to be given early
• OSELTAMIVIR
(NA)
• types A and B, needs to be given early
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OTHER TREATMENT
• REST, LIQUIDS, ANTI-FEBRILE AGENTS
(NO ASPIRIN FOR AGES 6MTHS-18YRS)
• BE AWARE OF COMPLICATIONS AND
TREAT APPROPRIATELY
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Paramyxoviridae
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Paramyxoviridae
• Genus
• Morbillivirus
• Paramyxovirus
• Pneumovirus
Human pathogen
Measles virus
Parainfluenza viruses,
Mumps virus
Respirtory syncytical
virus
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Virion
• Large virion consists of a negative RNA
genome in a helical nucleocapsid surrounded
by an enevlope containing a viral attachment
protein
• HN of paramyxovirus and mumps virus has
hemagglutinin and neuraminidase.
• H of measles virus has hemagglutinin activity
• G of RSV lacks these activities
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PARAMYXOVIRUSES
pleomorphic
HN/H/G glycoprotein
SPIKES
F glycoprotein
SPIKES
helical nucleocapsid (RNA plus
NP protein)
lipid bilayer membrane
polymerase
complex
M protein
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PARAMYXOVIRUS FAMILY
properties of attachment protein
GENUS
GLYCOPROTEINS
TYPICAL MEMBERS
Paramyxovirus
HN, F
HPIV1, HPIV3
HN, F
HPIV2, HPIV4
mumps virus
Morbillivirus
genus
H, F
measles virus
Pneumovirus
genus
G, F
respiratory
syncytial virus
genus
Rubulavirus
Genus
49
50
Replication , Pathogenesis and Immunity
• Virus replicates in the cytoplasm
• Virions penetrate the cell by fusion with the plasma
membrane
• Viruses induce cell-cell fusion, causing
multinucleated giant cells
• Paramyxoviridae are transmitted in respiratory
droplets and initiate infection in the respiratory tract
• Cell-mediated immunity causes many of the
symptoms but is essential for control of the infection
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MMR vaccine
• Composition : live attenuated virus
Measles / Mumps / Rubella
• Vaccination schedule: at 15-24 months and at
4 to 6 years or before junior high school
• Efficiency: 95% lifelong immunization with a
single dose
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Measles virus
（麻疹病毒）
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Pathogenesis and Immunity
• Childhood infection almost universal, protection
resulting from this is probably lifelong. Both man
and wild monkeys are commonly infected
• In culture, produces characteristic intranuclear
inclusion bodies and syncytial giant cells.
• Transmission and initial stages of disease similar to
mumps, but this virus can also infect via the eye
and multiply in the conjunctivae. Viraemia following
primary local multiplication results in widespread
distribution to many organs.
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Pathogenesis and Immunity
• After a 10-12 day incubation period
• Dry cough, sore throat, conjunctivitis (virus may be
excreted during this phase!), followed a few days
later by the characteristic red, maculopapular rash
and Koplik's spots
• Towards the end of the disease, there is extensive,
generalized virus infection in lymphoid tissues and
skin.
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viremia
57
DISSEMINATED SPREAD
• LONGER TIME FOR
SYMPTOMS
• IMMUNE RESPONSE
• IF SYMPTOMS DUE
TO IMMUNE
RESPONSE, USUALLY
INFECTIOUS PRIOR
TO SYMPTOMS
Adapted from Mims, Playfair, Roitt, Wakelin and Williams
(1993) Medical Microbiology
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MEASLES - Koplik’s spots
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Murray et al. Medical Microbiology
Koplik's spots
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MEASLES - RASH
CDC - B.Rice
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Murray et al. Medical Microbiology
DISEASE
• FEVER
• RESPIRATORY TRACT SYMPTOMS
• rhinorrhea, cough
• KOPLIK’S SPOTS
• MACULOPAPULAR RASH
• T-cells ->endothelial cells
• CONJUNCTIVITIS
• epithelial cells
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MEASLES GIANT CELL PNEUMONIA
Murray et al. Medical Microbiology
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Mims et al., Medical Microbiology 1993
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MEASLES ENCEPHALITIS
• 1/1000 cases
• sequelae
– deafness
– seizures
– mental disorders
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SSPE
• sub-acute sclerosing panencephalitis
– inflammatory disease
– defective virus
• early infection with measles is a risk factor
• rare (7/1,000,000 cases of measles)
• decrease since vaccination program
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Treatment
• No
69
Prevention
• Both live and killed vaccines exist.
Vaccination with the live attenuated vaccine
has been practised since the 1960's with a
dramatic decline in the incidence of the
disease .
• Trivalent live attenuated vaccine (MMR)
usually given - all of these viruses best
avoided during pregnancy!
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Mumps virus
（腮腺炎病毒）
71
Mumps virus
• Droplets spread the infection via saliva
and secretions from the respiratory
tract.
• Incubation period of 2-3 weeks
72
Mumps virus
• Malaise and fever is followed within a day by
painful enlargement of one or both of the parotid
(salivary) glands
• A possible complication in males after puberty is
orchitis - painful swelling of one or both testicles.
• Inflammation of the ovary and pancreas can also
occur.
• Disease is usually self-limiting within a few days
• Aseptic meningitis (usually resolving without
problems) or postexposure encephalitis (can prove
fatal) are the most serious complications
associated with mumps.
73
Prevention and treatment
• Treatment: none (passive immunization has
been used).
• Prevention: one invariant serotype therefore
vaccines are viable - both formalininactivated and live attenuated exist, the
latter now being widely used- see MMR.
74
MUMPS
CDC - B.Rice
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76
Mims et al., Medical Microbiology 1993
Mims et al., Medical Microbiology 1993
77
Parainfluenza virus
（副流感病毒）
78
Important Characteristics
• Typing: Four types (1-4) : distinguished
antigenically, by cytopathic effect, and
pathogenically
• Hemeagglutinin and fusion F protein is
found in the envelope
79
Pathogenesis and Immunity
• Cause acute respiratory infections of
man ranging from relatively mild
influenza-like illness to bronchitis, croup
(narrowing of airways which can result
in respiratory distress) and pneumonia;
common infection of children.
• Transmitted by aerosols.
80
Lab Diagnosis
• Nasopharynx specimen is culture in a
surrogate cell line in AGMK. Infected cell are
detected by hemeadsorption or DFA
• DFA also can be done rapidly to identify the
agent in direct specimen
• Serotypes 1-3 are comfirmed by
hemeagglutination inhibition using
standardized antisera
81
Treatment
• No antiviral therapy is available
• Nursing the patient in a humidified
atmosphere was commonly advised
• Dexamethasone地塞米松 and budesonide布
德松 have been approved ( for outpatient
treatments)
82
Prevention
• No, vaccines is not available
83
Respiratory syncytial virus
（呼吸道合胞病毒）
84
Important Characteristics
• RSV is highly infectious, transmission by respiratory
secretions.
• Primary multiplication occurs in epithelial cells of
URT producing a mild illness. In ~50% children less
than 8 months old, virus subsequently spreads into
the L.R.T. causing bronchitis, pneumonia and
croup.
• Has been suggested as a possible factor in cot
death and asthma.
85
Pathogenesis and immunity
Disorder
Bronchiolitis
pneumonia,
or both
Febrile rhinitis
and pharyngitis
Common cold
Age
Fever, cough, dyspnea, and
cyanosis in children younger
than 1 year
Children
Older children and adults
86
Lab Diagnosis
• DFA
• Cell culture of nasopharyngeal specimen
• A rise in antibody titre using ELISA
87
Treatment
• Ribavirin aerosol(三(氮)唑核苷,病毒唑) is
recommended for pneumonia in infants
• RSV - IGIV has been approved for infants
born prematurely
• IFN
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Prevention
• Currently no effective vaccine! Also, infection
does not result in lasting protection (c.f.
mumps, measles) therefore repeated
infections ('colds') occur throughout life usually without serious consequences in
adults.
89
Adenoviruses
（腺病毒）
90
General Concepts
• Most Adenovirus infections involve either the
respiratory or gastrointestinal tracts or the
eye.
Adenovirus infections are very common, most
are asymptomatic. Most people have been
infected with at least 1 type at age 15.
91
Adenovirus
92
Important Characteristics
93
94
Replication
95
Pathogenesis and Immunity
•
•
•
•
•
•
•
Disease:
Acute Respiratory Illness
Pharyngitis
Gastroenteritis
Conjunctivitis
Pneumonia
Keratoconjunctivitis
At Risk:
Military recruits, boarding schools,
Infants
Infants
All
Infants, military recruits
All
• Acute Haemorrhagic Cystitis Infants
• Hepatitis
Infants, liver transplant patients
96
swimming pool conjunctivitis
(游泳池结膜炎;红眼病)
• Eye infections characterized by a mild
conjunctivitis "swimming pool
conjunctivitis" are caused by
adenoviruses and have been linked to
transmission in contaminated
swimming pools.
97
swimming pool conjunctivitis
98
Lab Diagnosis
• Isolation of adenovirus can be accomplished in
cell cultures derived from epithelial cells
• Immunoassays, including fluorescent antibody
and enzyme-linked immunosorbent assays,
PCR can be used to detect and type the virus
in clinical samples and tissue cultures
• Serological assays such as CFA, HI, EIA and
neutralization techniques have been used to
detect specific antibodies.
99
Treatment
• No
100
Prevention
• Inactivated vaccines have been developed
and are routinely used for military recruits in
some countries
101
Rubella Virus
（风疹病毒）
102
General Concepts
• Viruses have enveloped single stranded
positive-sense RNA.
• Replication in cytoplasm and bud at plasma
membrane
• Cause Rubella( german measles, 3-days
measles)
103
Epidemiology
• Occurrence: worldwide in prevalence( in
winter and spring)
• Reservoir: Humans
• Mode of Transmission: Vertical transmission
in case of CRS/ Infection in nonimmune
children is usually transmitted by droplet
spread or by direct contact with patients
• Who is at risk: Non-immunized children are at
risk
104
• Incubation period: 2-3 weeks
Pathogenesis
Virus
Rubella enters and infects the
nasopharynx and lung and then
spreads to the lymph nodes and
reticuloendothelial system. The
resulting viremia spreads the virus
to other tissues and the skin.
Circulating antibody can block the
transfer of virus at the indicated
points. In an immunologically
deficient pregnant woman, the
virus can infect the placenta and
spread to the fetus
Congenital
infection 105
EFFECTS ON FETUS
• HEARING LOSS
• CONGENITAL HEART DEFECTS
• NEUROLOGICAL
– PYSCHOMOTOR AND/OR MENTAL
RETARDATION
• OPHTHALMIC
– CATARACT, GLAUCOMA, RETINOPATHY
106
EFFECTS ON FETUS
•
•
•
•
•
•
thrombocytopenia
hepatomegaly
splenomegaly
intrauterine growth retardation
bone lesions
pneumonitis
107
EFFECTS ON FETUS
• First trimester
– 65-85% of neonates have sequelae
108
EFFECTS ON FETUS
• 1964
– 20,000 infants with permanent problems
– 6,000 to 30,000 spontaneous abortions
– 5,000 therapeutic abortions
• 1969 to present
– maximum of 67 cases congential rubella/yr
• usually fewer than 10
109
CONGENITAL INFECTIONS
• SHED VIRUS FOR A YEAR OR MORE
AFTER BIRTH
– nasopharynx, urine, feces
110
CONGENITAL INFECTIONS
• EYE PROBLEMS
• GLANDULAR COMPLICATIONS
– diabetes,
– thyroid problems
– deficiency growth hormone
111
CONGENITAL / VERY EARLY
INFECTIONS
• PROGRESSIVE RUBELLA
PANENCEPHALITIS
112
Lab Diagnosis
• Current rubella infection, in pregnant women
can be confirmed by 4-fold rise in specific
antibody titer between acute and
convalescent-phase serum specimens by
ELISA
• The Dx of CRS in the newborn may be
confirmed by the presence of specific IgM
antibody.
113
Treatment
• There is no antiviral therapy available
114
Prevention
• A single dose of live, attenuated rubella
vaccine elicits a significant antibody response
in approximately 98%-99% of vaccinated
individuals
• It should not be given to
immunocompromised patients
115
Coronavirus
（冠状病毒）
116
Important Characteristics
• Virion: Spherical, 80-160nm in diameter, helical
nucleocapside
• Genome: +ssRNA, linear, nonsegmented, 27-30kb,
infectious
• Proteome: two glycoproteins and one
phosphoprotein. Some viruses contain a third
glycoprotein (hemagglutinin esterase)
• Envelope: contains large, widely spaced, club-or
petal- shaped spikes. crown-like
117
Virion structure
• S-Spike
glycoprotein:
receptor binding,
cell fusion, major
antigen
• M-Membrane
glycoprotein:
transmembrane budding &
envelope
formation
118
Pathogenesis and Immunity
• These viruses infect a variety of mammals &
birds. The exact number of human isolates are
not known as many cannot be grown in
culture.
• They cause: common colds and have been
implicated in gastroenteritis in infants.
• Transmitted by aerosols of respiratory
secretions
119
Rhinovirus
（鼻病毒）
120
Important Characteristics
• Rhinoviruses are picornaviruses similar to
enteroviruses but differ from them in having a
buoyant density in cesium chloride of 1.40
g/ml and in being Acid-labile
• Rhinoviruses are isolated commonly from
the nose and throat but very rarely from
feces.
• These viruses cause upper respiratory
tract infections, including the common
cold
121
Reovirus
(呼肠孤病毒)
122
Important Characteristics
• Virion: Icosahedal, 60-80nm in diameter,
double capsid shell
• Genome: dsRNA
• Envelope: none
• Diseases: Acute respiratory tract infection
and Gastrointestinal infections
123