Download An Overview Of The Communicable Disease Situation In Singapore

An Overview Of The
Communicable
Disease Situation In
Singapore, 2000
An Overview Of The Communicable
Disease Situation In Singapore, 2000 ........................... 1 - 1
Communicable
Disease
I
AN OVERVIEW OF THE COMMUNICABLE
DISEASE SITUATION IN SINGAPORE, 2000
The infectious disease situation in Singapore was closely monitored through a comprehensive and well-established system of epidemiological surveillance (Fig.1.1).
A high level of vigilance on the disease activity was also maintained on emerging infectious
diseases throughout the world to prevent their introduction into Singapore as far as possible and to
deal with them swiftly and effectively should they be introduced. As of 1st of October 2000, three
new infectious diseases were made legally notifiable, viz. hand, foot and mouth disease, legionellosis
and Nipah virus infection. Table 1.1 gives the list of notifiable diseases.
The morbidity, mortality and case-fatality rates of the infectious diseases notifiable to the
Ministry of the Environment in 2000 and the trend of vector-borne, food-borne and air-borne diseases are shown in Table 1.2 and Fig. 1.2, respectively.
Vector-borne diseases
There was a marked decrease in the incidence of dengue fever (DF)/dengue haemorrhagic
fever (DHF) from 1,355 cases in 1999 to 673 cases in 2000. Two deaths were reported. The
Figure 1.1
System for notification of infectious diseases
Department of
Pathology
Singapore General
Hospital
Private Medical
Practitioners
SAF Medical Corps
MINDEF
Ministry
of Health
Death
Ministry
of the Environment
Registry
Department of
Mircobiology
National University
of Singapore
Hospitals
Family Health
Service
School Health
Clinical
Service
Laboratories
OTHER001/CMH/300399
An Overview Of The Communicable
Disease Situation In Singapore, 2000 ........................... 1 - 1
Table 1.1
Notifiable diseases in Singapore
Notifiable to ENV under the
Infectious Diseases Act
Notifiable to MOH under the
Infectious Diseases Act
Chickenpox
Tuberculosis
Cholera
Venereal diseases
Dengue
- Chancroid
Dengue haemorrhagic fever
- Gonorrhoea
Diphtheria
- Non-specific urethritis
Encephalitis
- Syphilis
Viral hepatitis
Malaria
- AIDS/HIV infection
Leprosy
Poliomyelitis
Plague
Typhoid
Paratyphoid
Mumps
Hand, foot and mouth disease
Yellow fever
Measles
Rubella
Legionellosis
Nipah virus infection
Administratively notifiable to ENV
Food-borne diseases
- Campylobacteriosis
- E. coli 0157
- Salmonellosis
- Listeriosis
- Food poisoning
Rodent-borne diseases
- Typhus
- Leptospirosis
- Hantavirus infection
Environment-related diseases
- Melioidosis
- Cryptococcosis
Vaccine-preventable diseases
- Meningococcal meningitis
- Haemophilus influenza B
An Overview Of The Communicable
Disease Situation In Singapore, 2000 ........................... 1 - 2
Table 1.2
Morbidity, mortality and case-fatality rates of notifiable infectious diseases in Singapore, 2000
Diseases
No. of cases
10 (3)
Cholera
Rate per 100,000 population*
Morbidity rate
Mortality rate
Casefatality
rate (%)
0
0.3
0
0
No. of
deaths
Plague
0
0
0
0
0
Yellow Fever
0
0
0
0
0
24,074
1
737.7
0.03
0.004
Chickenpox
DF/DHF
DF
DHF
673 (271)
2 (2)
20.6
0.06
0.3
663 (265)
0
20.3
0
0
10 (6)
Diphtheria
0
2 (2)
0.3
0.06
20
0
0
0
0
Enteric fevers
101 (85)
0
3.1
0
0
Typhoid fever
80 (66)
0
2.5
0
0
Paratyphoid fever
21 (19)
0
0.6
0
0
3 (3)
8.2
0.09
1.1
0
0
0
0
266 (264)
Malaria
Poliomyelitis
0
Viral hepatitis
211 (152)
4
6.5
0.12
1.9
Hepatitis A
77 (63)
0
2.4
0
0
Hepatitis B
117 (74)
0
3.6
0
0
Hepatitis E
17 (14)
0
0.5
0
0
4
2
0.12
0.06
Japanese encephalitis
0
0
0
0
Other
4
2
0.12
0.06
0
4.3
0
0
0
0
Viral encephalitis
141 (40)
Measles
5,981
Mumps
312 (39)
Rubella
0
183
50
0
50
0
9.6
0
0
0
0
Nipah virus infection+
0
0
0
Hand, foot and mouth
disease+
6,402
4
196.2
0.12
0.06
3
2.0
0.09
4.6
Legionellosis+
( )
65 (10)
Imported cases
*
Rates are based on 2000 census population obtained from the Department of Statistics
+
Notifiable as from 1 Oct 2000
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Disease Situation In Singapore, 2000 ........................... 1 - 3
Figure 1.2
Annual incidence rates of specified vector-borne, food-borne
and air-borne diseases in Singapore, 1990 - 2000
Vector-borne diseases
R a te p e r 1 0 0 ,0 0 0 p o p u la tio n
200
D e n g u e fe ve r/d e n g u e h a e m o rrh a g ic fe ve r
Ja p a n e se e n ce p h a litis+
150
M a la ria
100
50
0
R a te p e r 1 0 0 ,0 0 0 p o p u la tio n
50
Food-borne diseases
C h o le ra
T y p h o id fe ve r
40
P a ra typ h o id fe ve r
H e p a titis A
30
F o o d p o iso n in g
20
10
0
Air-borne diseases
R a te p e r 1 0 0 ,0 0 0 p o p u la tio n
2000
M e a sle s
C h icke n p o x
M um ps
1500
R u b e lla
1000
500
0
91
92
93
94
95
96
97
98
99
00
Ye a r
* No local cases of diphtheria and poliomyelitis were reported during this period
+ Three cases of Japanese encephalitis were reported in 1990, one imported case in 1996,
two imported cases in 1997, one imported case in 1998and one imported case in 1999
MIX002/CMH/111001
An Overview Of The Communicable
Disease Situation In Singapore, 2000 ........................... 1 - 4
incidence rate was highest in the 15-24 year age group. Residents of compound houses had an
incidence rate five times higher than that of HDB flat dwellers. Most of these occurred in the southeastern and southern parts of the island. The main circulating dengue virus serotypes were dengue 1 and dengue 2.
A total of 266 cases of malaria, including three deaths from falciparum malaria, were reported. Virtually all the cases were imported, mainly from the Indian subcontinent and Southeast
Asia. Two sporadic cases with no recent travel history could have acquired the infection locally.
No case of Japanese encephalitis was reported.
Food-borne diseases
The incidence of cholera remained low with 7 indigenous and 3 imported cases reported. A
local resident was infected with Vibrio cholerae 0139. This strain was last isolated in 1993 and
1994 among imported cases from India and Thailand.
The incidence of indigenous typhoid and paratyphoid was also low with 14 and 2 cases,
respectively, reported. Majority of the notified cases of typhoid (82.5%) and paratyphoid (90.5%)
were imported.
A large proportion of the hepatitis A (81.8%) and hepatitis E (82.4%) cases were imported.
Only 14 indigenous cases of hepatitis A and 3 indigenous cases of hepatitis E cases were reported.
In 2000, there were 213 food poisoning notifications involving 1,542 cases. A common
source food-borne outbreak of 269 cases in a secondary school was associated with the consumption of contaminated iced drink made from non-food-grade ice. A water-borne outbreak of
122 cases of gastroenteritis occurred in a shopping/office/residential complex at Bukit Timah.
Investigation showed that the basement water tanks were contaminated with sewage leaking from
the sewerage pipes located above a tank with missing cover.
An outbreak of multidrug resistant Salmonella typhimurium definite type 104, involving mainly
children below 18 months of age, was traced to the consumption of undercooked ground “ikan
bilis”.
Two cases of ciguatera fish poisoning were reported. The diagnosis was based on the
typical clinical presentations. Ciguatoxin could not be detected in the implicated oral-reef fish
imported from Fiji.
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Disease Situation In Singapore, 2000 ........................... 1 - 5
Air-borne diseases
There were 509,966 attendances at restructured polyclinics for acute respiratory illnesses
and 26,077 attendances for conjunctivitis. Influenza A and B viruses were detected throughout
the year. Influenza A (H3N2), circulated in the beginning of the year and was replaced by the A
(H1N1) strains in Mar-Jun. An increase in polyclinic attendances for conjunctivitis was noted
during the Aug-Oct period. No virus study was carried out.
The number of chickenpox decreased from 31,592 cases in 1999 to 24,074 cases in 2000.
The resurgence of mumps, which started in 1999, declined by 6% with 5,981 cases reported in
2000. The resurgence was due to poor protection conferred by the Rubini mumps virus strain of
the Swiss MMR vaccine, which was subsequently deregistered. The incidence rate was highest in
children 5-14 years of age. Rubella incidence also declined from 432 cases in 1999 to 312 cases
in 2000. The incidence of measles increased from 65 cases in 1999 to 141 cases in 2000. The
incidence rate was highest in pre-school children below 5 year of age. No local cases of diphtheria
or poliomyelitis were reported.
Environment-related diseases
A total of 65 cases of legionellosis were reported in 2000 compared to 79 cases in the
previous year. The diagnosis was mainly based on serological finding of a single blood specimen
(indirect fluorescent antibody titre of ≥1:1024) in the presence of characteristic clinical presentation. About 70% of the cases had concurrent medical illness. The incidence rate was highest in
those above 65 years age. Of the cooling towers tested during the year, 59.5% were positive for
legionella bacteria.
The incidence of melioidosis remained stable with 77 cases reported. The highest incidence rate was among the elderly aged 65 years and above. Almost all the cases had some
underlying medical conditions. There had been a sharp reduction in case-fatality rates from 60%
in 1990 to 12% in 2000. This could be due to greater awareness among medical practitioners to
diagnose and treat the disease early, as reflected by the decreasing proportion of bacteraemic
cases from 91% to 36.4% during the same period.
Emerging diseases
Following reports of outbreaks of hand, foot and mouth disease (HFMD) in Sarawak in 1997
and Taiwan in 1998, a close surveillance of the disease was maintained in Singapore. A Standard
Operation Procedure (SOP) was prepared and the HFMD Task Force established.
An Overview Of The Communicable
Disease Situation In Singapore, 2000 ........................... 1 - 6
In September 2000, 4 deaths, including 2 siblings, were reported. Enterovirus 71 was isolated from the brain, lung and throat swabs of the 2 siblings. These deaths occurred when the
disease incidence was increasing rapidly. With the notification of the deaths of the two siblings,
the Task Force immediately activated the SOP by closing down all preschool centres from 1 Oct –
16 Oct 2000. The measure taken was effective in reducing transmission among preschool children. The incidence dropped sharply from a peak of 308 cases per day on 10 Oct to 10 cases per
day on 28 Oct.
In April 2000, 6 cases of meningococcal disease, including one death, related to travel to
Saudi Arabia were reported in Singapore. The disease was caused by an uncommon strain of
Neisseria meningitidis serogroup W135. Two of the cases were family contacts of returning Haj
pilgrims. Following this outbreak, the bivalent meningococcal vaccine (A/C) was replaced by the
quadrivalent (A/C/Y/W135) vaccine for all Haj pilgrims.
Campylobacter enteritits has been increasing from 84 cases in 1994 to 343 cases in 1999.
It then dropped to 231 cases in the following year. The incidence rate was highest in preschool
children below 5 years of age. The risk factor identified through a case-control study was failure of
caregivers to wash their hands after handling raw poultry and before preparing milk formula. The
Agri-food Veterinary Authority of Singapore is taking measures to reduce the high prevalence of
Campylobacter contamination of imported poultry.
An imported case of diarrhoea caused by E. coli O157:H7 and an imported case of listerosis
were notified during the year.
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