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• Campylobacteriosis• Cholera• Enteric fevers (Typhoid and Paratyphoid)• Hepatitis A and E• Listeriosis• Salmonellosis• Shigellosis• Food Poisoning
Air-/D
roplet-B
orneD
iseases
Vector-Borne/
ZoonoticD
iseases
Food-/Water-
Borne
Diseases
Blood-B
orneD
iseasesE
nvironment-
Related
Diseases
Childhood
Imm
unisation
Communicable Diseases Surveillance in Singapore 2003
IIIFOOD-/WATER-BORNE DISEASES
Food-borne diseases are caused by the ingestion of foodstuffs or water contaminated by:
CAMPYLOBACTERIOSISCampylobacter enteritis is an acute bacterial enteric disease of variable severity characterised by diarrhoea, abdominal pain, malaise, fever, nausea and vomiting. Campylobacter jejuni and less commonly, C. coli are the usual causes of Campylobacter enteritis in humans. The mode of transmission is by ingestion of the organisms in undercooked chicken and pork, contaminated food and water or unpasteurised milk.
There were 144 cases of Campylobacter gastroenteritis reported in 2003. In the majority of the cases, Campylobacter jejuni was isolated. (Table 3.1) The highest incidence rate (39.5/100,000) was in children below five years of age. (Table 3.2) Amongst the three major ethnic groups, the incidence was highest in Malay residents. (Table 3.3)
C. coli
4
1
19
3
0
0
0
0
0
1
Year
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
C. laridis
0
0
0
0
4
3
1
0
0
0
Other species
0
0
0
0
11
17
4
0
0
0
Unknown
0
0
0
0
0
0
0
0
0
3
Total
84
102
107
121
269
343
231
105
50
144
No. of cases caused by
*Based on estimated mid-year total population of the respective year(Source: Singapore Department of Statistics)
Table 3.1Incidence of reported Campylobacter enteritis, 1994-2003
C. jejuni
80
101
88
118
254
323
226
105
50
140
Incidence rateper 100,000 population*
2.5
2.9
2.9
3.2
6.9
8.7
5.8
2.5
1.2
3.4
45
(2) bacterial, viral or parasitic agents
(3) toxins produced by harmful algal species or (4) heavy metals and other organic compounds.
(1) toxins associated with bacterial growth in the food
present in specific fish species
Table 3.2Age-gender distribution and age-specific incidence rates of reported
Campylobacter enteritis, 2003
Male
52
21
2
1
2
4
5
87
Age (Yrs)
0 – 4
5 – 14
15 – 24
25 – 34
35 – 44
45 – 54
55+
Total
Total (%)
85 (59.0)
34 (23.6)
4 (2.8)
3 (2.1)
4 (2.8)
4 (2.8)
10 (6.9)
144 (100.0)
Female
33
13
2
2
2
0
5
57
Incidence rateper 100,000 population*
39.5
6.3
0.6
0.3
0.5
0.7
1.7
3.4
* Rates are based on estimated mid-year resident population, 2003(Source: Singapore Department of Statistics)
Table 3.3Ethnic-gender distribution and ethnic-specific incidence rates of reported
Campylobacter enteritis, 2003
Singapore Resident
Chinese
Malay
Indian
Others
Foreigner
Total
Cases (%)
84 (58.3)
28 (19.5)
10 (6.9)
8 (5.6)
14 (9.7)
144 (100.0)
Incidence rateper 100,000 population*
* Rates are based on estimated mid-year population, 2003(Source: Singapore Department of Statistics)
3.2
5.9
3.5
13.6
1.9
3.4
Male
49
15
8
3
12
87
Female
35
13
2
5
2
57
46
Communicable Diseases Surveillance in Singapore 2003
CHOLERACholera is an acute bacterial enteric disease characterised in its severe form by sudden onset, profuse painless watery stools, nausea and vomiting. Untreated cases proceed rapidly to dehydration, acidosis, hypoglycaemia, circulatory collapse and renal failure. The usual causative agent in Singapore is Vibrio cholerae serogroup O1 which includes two biotypes, Classical and El Tor. Each of these biotypes can be further classified into serotypes Inaba, Ogawa and Hikojima. Other serogroups in addition to O1 are O139 and Non O but these have not been seen in Singapore. The mode of transmission is through ingestion of food or
water contaminated with faeces or vomitus of infected persons.
In 2003, there were 2 reported cases of cholera. Both were aged over 55 years. One had a travel history to Thailand and the identified causative agent was Vibrio cholera O1, biotype El Tor serotype Inaba. The other was an 80-year-old local housewife with no travel history, who tested positive for V. cholera O1, biotype El Tor serotype Ogawa.
The overall incidence rate was 0.05 per 100,000 population. (Table 3.4)
Male
0
0
0
0
0
0
0
0
Age (Yrs)
0 – 4
5 – 14
15 – 24
25 – 34
35 – 44
45 – 54
55+
Total
Total (%)
0 (0.0)
0 (0.0)
0 (0.0)
0 (0.0)
0 (0.0)
0 (0.0)
2 (100.0)
2 (100.0)
Female
0
0
0
0
0
0
2
2
Incidence rateper 100,000 population*
0.0
0.0
0.0
0.0
0.0
0.0
0.3
0.05*Rates are based on 2003 estimated mid-year population.
(Source: Singapore Department of Statistics)
Table 3.4Age-gender distribution and age-specific incidence rates of reported cholera cases, 2003
Figure 3.1Reported cholera cases, 1994-2003
0
5
10
15
20
25
30
35
40
45
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003
Year
Num
ber o
f cas
es
ImportedLocal
47
ENTERIC FEVERSEnteric fevers are systemic, bacterial diseases characterised by insidious onset of sustained fever, severe headache, malaise, anorexia. Other features may include a relative bradycardia, splenomegaly, non-productive cough (in the early stage of the illness). Constipation is more common than diarrhoea in adults. Typhoid and paratyphoid fevers are collectively known as enteric fevers and the causative organisms are Salmonella typhi and Salmonella paratyphi
(types A, B or C). The mode of transmission is via food and water contaminated by faeces and urine of patients and carriers. From 1999 to 2003, a total of 395 enteric fever cases were notified. Typhoid made up 291 (74%) of cases. The majority of the enteric fever cases (88%) were local residents who had acquired the illness whilst overseas. (Table 3.5)
Year
1999
2000
2001
2002
2003
Total
Paratyphoid
( ) Cases acquired overseas
Table 3.5Classification of reported enteric fever cases, 1999-2003
Typhoid
48 (39)
80 (66)
82 (71)
49 (43)
32 (31)
291 (250)
A
15 (15)
21 (19)
34 (30)
25 (23)
9 (9)
104 (96)
B
0
0
0
0
0
0
C
0
0
0
0
0
0
Total
63 (54)
101 (85)
116 (101)
74 (66)
41 (40)
395 (346)
In 2003, there were 41 reported cases of enteric fevers, compared to 74 cases in 2002, with more cases being reported in the months of June and July. (Figure 3.2) Of these, 32
cases were typhoid fever and nine paratyphoid fever type A. As in previous years the majority of enteric fever cases were local residents who had acquired the illness whilst overseas.
0
2
4
6
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53
Week
No.
of c
ases
2002 2003
Figure 3.2E-weekly distribution of reported enteric fever cases, 2002 - 2003
Male
1
1
5
3
1
1
1
13
Age (Yrs)
0 – 4
5 – 14
15 – 24
25 – 34
35 – 44
45 – 54
55+
Total
Total (%)
1 (5.0)
4 (20.0)
8 (40.0)
4 (20.0)
1 (5.0)
1(5.0)
1 (5.0)
20 (100.0)
Female
0
3
3
1
0
0
0
7
Incidence rateper 100,000 population*
0.5
0.7
1.3
0.5
0.1
0.2
0.2
0.5
^Excluding 10 foreigners seeking medical treatment in Singapore and 2 tourists*Rates are based on 2003 estimated mid-year population.
(Source: Singapore Department of Statistics)
Table 3.7Age-gender distribution and age-specific incidence rates of reported typhoid cases^, 2003
48
Communicable Diseases Surveillance in Singapore 2003
Table 3.6Classification of reported typhoid and paratyphoid cases, 2003
Population Group
Local residents
Foreigners seeking medical treatment in Singapore
Tourists
Total
Typhoid No. (%)
20 (62.5)
10 (31.3)
2 (6.2)
32 (100.0)
Paratyphoid No. (%)
8 (88.9)
1(11.1)
0 (0.0)
9 (100.0)
Typhoid FeverAmong the 32 reported typhoid cases, there were 20 local residents, 10 foreigners seeking medical treatment in Singapore and two tourists. (Table 3.6) In local residents, 40% occurred in the 15-24
years age group. (Table 3.7) Foreigners residing in Singapore accounted for 40% of these 20 cases. (Table 3.8)
Male
1
1
5
3
1
1
1
13
Age (Yrs)
0 – 4
5 – 14
15 – 24
25 – 34
35 – 44
45 – 54
55+
Total
Total (%)
1 (5.0)
4 (20.0)
8 (40.0)
4 (20.0)
1 (5.0)
1(5.0)
1 (5.0)
20 (100.0)
Female
0
3
3
1
0
0
0
7
Incidence rateper 100,000 population*
0.5
0.7
1.3
0.5
0.1
0.2
0.2
0.5
^Excluding 10 foreigners seeking medical treatment in Singapore and 2 tourists*Rates are based on 2003 estimated mid-year population.
(Source: Singapore Department of Statistics)
Table 3.7Age-gender distribution and age-specific incidence rates of reported typhoid cases^, 2003
Table 3.8Ethnic-gender distribution and ethnic-specific incidence rates of reported typhoid cases^, 2003
^Excluding 10 foreigners seeking medical treatment in Singapore and 2 tourists*Rates are based on 2003 estimated mid-year population.
(Source: Singapore Department of Statistics)
Male
4
0
0
3
6
13
Singapore Resident
Chinese
Malay
Indian
Others
Foreigner
Total
Total (%)
5 (25.0)
0 (0.0)
3 (15.0)
4 ( 20.0)
8 (40.0)
20 (100.0)
Female
1
0
3
1
2
7
Incidence rateper 100,000 population*
0.2
0.0
1.1
6.8
1.1
0.5
49
The overall incidence rate of typhoid was 0.5 per 100,000 population. One local case did not have any history of recent travel, but had taken food prepared by a foreign domestic worker whose stool culture was positive for the causative agent.Of the 11 cases involving local residents who
contracted typhoid fever overseas, most travel destinations included Indonesia (54.5%) and India (45.5%). (Table 3.9) The purposes for their travel included pleasure/vacation (36.3%), social visits (27.3%), business/employment (27.3%) and others (9.1%). (Table 3.10)
Table 3.9Singapore residents who contracted typhoid overseas by country of origin, 1999-2003
Table 3.10Singapore residents who contracted typhoid overseas by purpose of travel, 1999-2003
Classification 1999 2000 2001 2002 2003No. (%) No. (%) No. (%) No. (%) No. (%)
Country visitedIndonesia 11 (78.6) 7 (33.3) 11 (47.8) 6 (50.0) 6 (54.5)India 2 (14.3) 10 (47.6) 4 (17.4) 3 (25.0) 5 (45.5)Malaysia 0 (0.0) 1 (4.8) 4 (17.4) 1 (8.3) 0 (0.0)Thailand 0 (0.0) 0 (0.0) 2 (8.7) 1 (8.3) 0 (0.0)Pakistan 1 (7.1) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)Myanmar 0 (0.0) 3 (14.3) 0 (0.0) 0 (0.0) 0 (0.0)Nepal 0 (0.0) 0 (0.0) 1 (4.3) 0 (0.0) 0 (0.0)China 0 (0.0) 0 (0.0) 1 (4.3) 1 (8.3) 0 (0.0)
Total 14 (100.0) 21 (100.0) 23 (100.0) 12 (100.0) 11 (100.0)
Classification 1999 2000 2001 2002 2003No. (%) No. (%) No. (%) No. (%) No. (%)
Purpose of TravelSocial visits 5 (35.7) 4 (19.0) 7 (30.4) 3 (25.0) 3 (27.3)Pleasure/vacation 8 (57.1) 13 (62.0) 8 (34.8) 4 (33.3) 4 (36.3)Business/employment 1(7.2) 4 (19.0) 7 (30.4) 5 (41.7) 3 (27.3)Pilgrimage 0 (0.0) 0 (0.0) 1 ( 4.4) 0 (0.0) 0 (0.0)Others 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 1 (9.1)
Total 14 (100.0) 21 (100.0) 23 (100.0) 12 (100.0) 11 (100.0)
50
Communicable Diseases Surveillance in Singapore 2003
Paratyphoid Fever
Among the nine reported paratyphoid cases, eight involved local residents. Five acquired their illness overseas and three were work permit holders. Overall incidence of paratyphoid fever
among local residents in 2003 was 0.2 per 100,000 population. Half of the cases (50%) were in the 25-34 years age group (Table 3.11) and the majority were foreigners (37.5%). (Table 3.12)
Male
0
0
0
3
1
1
0
5
Age (Yrs)
0 – 4
5 – 14
15 – 24
25 – 34
35 – 44
45 – 54
55+
Total
Total (%)
1 (12.5)
1 (12.5)
0 (0.0)
4 (50.0)
1 (12.5)
1 (12.5)
0 (0.0)
8 (100.0)
Female
1
1
0
1
0
0
0
3
Incidence rateper 100,000 population*
0.5
0.2
0.0
0.5
0.1
0.2
0.0
0.2
^Excluding 1 foreigner seeking medical treatment in Singapore.*Rates are based on 2003 estimated mid-year population.
(Source: Singapore Department of Statistics)
Table 3.11Age-gender distribution and age-specific incidence rates of reported paratyphoid cases^, 2003
Table 3.12Ethnic-gender distribution and ethnic-specific incidence rates of reported paratyphoid cases^, 2003
^Excluding 1 foreigner seeking medical treatment in Singapore.*Rates are based on 2003 estimated mid-year population.
(Source: Singapore Department of Statistics)
Male
1
1
0
0
3
5
Singapore Resident
Chinese
Malay
Indian
Others
Foreigner
Total
Female
1
0
1
1
0
3
Total (%)
2 (25.0)
1 (12.5)
1 (12.5)
1 (12.5)
3 (37.5)
8 (100.0)
Incidence rateper 100,000 population*
0.1
0.2
0.4
1.7
0.4
0.2
51
The purposes of travel for the five local residents who contracted the disease while overseas were
pleasure/vacation (20%), business/ employment (60%) and social visits (20%). (Table 3.13)
Purpose of travel
Social visits
Pleasure/vacation
Business/employment
Military training
Total
1999
No. (%)
2 (28.6)
1 (14.3)
4 (57.1)
0 (0.0)
7 (100.0)
2000
No. (%)
1 (16.7)
4 (66.6)
0 (0.0)
1 (16.7)
6 (100.0)
2001
No. (%)
3 (17.6)
10 (58.9)
4 (23.5)
0 (0.0)
17 (100.0)
2002
No. (%)
1 (9.1)
4 (36.4)
5 (45.4)
1 (9.1)
11 (100.0)
2003
No. (%)
1 (20.0)
1 (20.0)
3 (60.0)
0 (0.0)
5 (100.0)
Table 3.13Singapore residents who contracted paratyphoid overseas by purpose of travel, 1999-2003
Classification
HEPATITIS A AND EHepatitis A is a viral infection spread from person to person by the faecal-oral route. Foods that are eaten raw or partially cooked, prepared with contaminated water or by an infected food handler are common sources of infection.
For viral hepatitis E, the mode of transmission is the same as viral hepatitis A. The most common documented mechanism of transmission is via faecally contaminated drinking water.
In 2003, 55 cases of serologically confirmed viral hepatitis A and 17 cases of viral hepatitis E were reported as compared to 236 cases and 24 cases respectively in 2002. (Figures 3.3 and 3.4) Of the total reported, four cases of viral hepatitis A and two cases of viral hepatitis E involved patients seeking medical treatment in Singapore. Two viral hepatitis A cases were tourists.
52
Communicable Diseases Surveillance in Singapore 2003
Figure 3.3E-weekly distribution of reported hepatitis A cases, 2002 - 2003
Figure 3.4E-weekly distribution of reported hepatitis E cases, 2002 - 2003
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53
2002 2003
No.
of c
ases
32
28
24
20
16
12
8
4
0
No.
of c
ases
6
4
2
0
2002 2003
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53
Week
Week
53
Figure 3.5Geographical distribution of indigenous acute hepatitis A, 2003
One acute hepatitis A case
The geographical distributions of acute hepatitis A and E indigenous cases are shown
Figure 3.6Geographical distribution of indigenous acute hepatitis E, 2003
One acute hepatitis E case
in Figures 3.5 and 3.6 respectively. Various occupational groups were involved. (Table 3.14)
54
Communicable Diseases Surveillance in Singapore 2003
Table 3.14Distribution of acute hepatitis A & E cases^ by occupation, 2003
A
1
1
1
1
2
0
5
4
2
1
1
1
1
1
1
1
1
0
1
1
1
0
6
2
2
0
11
49
Occupation
Children under 4 years of age
Cleaners, labourers and related workers
Attendants
Construction labourers and related workers
Domestic helpers (general)
Legislators, senior officials and manager
Businessman
Director
Managers
Professionals
Engineers/technicians/electricians
Medical doctors/nurses
Reporter
Plant and machine operators and assemblers
Seaman
Drivers
Production craftsmen and related workers
Supervisor and general foreman
Worker (Building maintenance)
Self employed
Service workers and shop/market sales workers
Sales (Demonstrator)
Technicians and Associate Professionals
Immigration Officer
Insurance sales agent and broker
Management executive
Pharmaceutical assistant/dispenser
Technician (Building)
Unclassified
Army
Students
Housewives
Unemployed
Not applicable
Unknown
Total
Total
1
1
2
1
2
2
5
4
2
1
1
2
1
2
2
1
1
1
1
1
1
1
6
3
4
0
15
64
E
0
0
1
0
0
2
0
0
0
0
0
1
0
1
1
0
0
1
0
0
0
1
0
1
2
0
4
15
%
1.6
1.6
3.1
1.6
3.1
3.1
7.8
6.2
3.1
1.6
1.6
3.1
1.6
3.1
3.1
1.6
1.6
1.6
1.6
1.6
1.6
1.6
9.3
4.6
6.2
0.0
23.4
100.0
Hepatitis
^Excluding foreigners seeking medical treatment in SIngapore and tourists.
55
Among local residents, the age-specific incidence rate of acute hepatitis A was highest in the 35-44 years age group (1.9/100,000), but for hepatitis E the highest incidence is skewed towards the 45-54
years age group (0.9/100,000). The overall male to female ratio was 1.6:1 for acute hepatitis A and 6.5:1 for acute hepatitis E. (Table 3.15)
Male
1
4
3
8
7
2
5
30
Age (Yrs)
0 – 4
5 – 14
15 – 24
25 – 34
35 – 44
45 – 54
55+
Total
Total (%)
1(2.0)
6(12.3)
8(16.3)
11(22.5)
15(30.6)
3(6.1)
5(10.2)
49(100.0)
Female
0
2
5
3
8
1
0
19
Incidence rate per 100,000 population*
0.5
1.1
1.3
1.3
1.9
0.5
0.8
1.2
^Excluding 4 cases of hepatitis A, 2 cases of hepatitis E seeking medical treatment in Singapore and 2 tourists diagnosed with hepatitis A.*Rates are based on 2003 estimated mid-year population.
(Source: Singapore Department of Statistics)
Table 3.15Age-gender distribution and age-specific incidence rates of acute hepatitis A & E^, 2003
Male
0
0
1
3
3
5
1
13
Total (%)
0(0.0)
0(0.0)
1(6.7)
4(26.7)
4(26.7)
5(33.3)
1(6.7)
15(100.0)
Female
0
0
0
1
1
0
0
2
Incidence rate per 100,000 population*
0.0
0.0
0.2
0.5
0.5
0.9
0.2
0.4
Hepatitis A Hepatitis E
The incidence rate of hepatitis A in Indian residents is approximately twice that of Malays and Chinese.
Chinese residents and foreigners dominated those with hepatitis E in 2003. (Table 3.16)
56
Table 3.16Ethnic-gender distribution and ethnic-specific incidence rates of acute hepatitis A & E^, 2003
Male
19
3
2
1
5
30
Total (%)
30(61.2)
4(8.2)
6(12.3)
1(2.0)
8(16.3)
49(100.0)
Female
11
1
4
0
3
19
Incidence rate per 100,000 population*
1.1
0.8
2.1
1.7
1.1
1.2
^Excluding 4 cases of hepatitis A, 2 cases of hepatitis E seeking medical treatment in Singapore and 2 tourists diagnosed with hepatitis A.*Rates are based on 2003 estimated mid-year population.
(Source: Singapore Department of Statistics)
Male
10
0
0
0
3
13
Total (%)
12(80.0)
0(0.0)
0(0.0)
0(0.0)
3(20.0)
15(100.0)
Female
2
0
0
0
0
2
Incidence rate per 100,000 population*
0.5
0.0
0.0
0.0
0.4
0.4
Hepatitis A Hepatitis E
Chinese
Malay
Indian
Others
Foreigner
Total
Singapore Resident
Communicable Diseases Surveillance in Singapore 2003
Overseas-acquired viral hepatitisOf the 55 cases of hepatitis A and 17 cases of hepatitis E, 39 (70.9%) and 9 (52.9%) respectively were acquired overseas. (Table 3.17) The majority of cases acquired the infection from Southeast Asia (56.3%) and the Indian subcontinent (37.5%).
Table 3.17Overseas acquired acute hepatitis cases
by country of origin, 2003
Country of origin
Southeast Asia
Cambodia
Indonesia
Malaysia
Philippines
Thailand
Indian subcontinent
Bangladesh
India
Nepal
Pakistan
Other Asian countries
China
Others
Australia
Unknown
Total
A
0
13
5
2
1
2
8
1
4
1
1
1
39
E
1
0
5
0
0
2
1
0
0
0
0
0
9
Total
1
13
10
2
1
4
9
1
4
1
1
1
48
%
2.1
27.1
20.8
4.2
2.1
8.3
18.8
2.1
8.3
2.1
2.1
2.1
100.0
Hepatitis
Thirty-three (67.3%) local residents acquired hepatitis A and 7 (46.7%) acquired hepatitis E overseas. (Table 3.18)
Table 3.18Classification of overseas-acquired acute hepatitis cases by population group, 2003
Population Group
Singapore residents who contracted the disease overseas
Foreigners seeking medical treatment in Singapore
Work permit/employment pass holders
Tourists
Others
Total
HepatitisA
27
4
5
2
1
39
HepatitisE
4
2
3
0
0
9
%
64.6
12.5
16.7
4.1
2.1
100.0
Total
31
6
8
2
1
48
No. of cases
The purpose of travel for the 27 Singapore residents who contracted the diseases overseas was mainly for vacation. (Table 3.19)
Table 3.19Purpose of travel for Singapore residents who
contracted acute hepatitis A & E overseas, 2003
Purpose
Visit friends/relatives
Business/employment/study
Pleasure/vacation
Others
Total
No. of cases
3
10
14
0
27
%
11.1
37.0
51.9
0.0
100.0
Hepatitis A
No. ofcases
1
1
2
0
4
%
25.0
25.0
50.0
0.0
100.0
Hepatitis E
57
Consumption of shellfishThere was no significant association between shellfish consumption and hepatitis A. Of the 55 sporadic cases of hepatitis A, four (7.3%) gave a history of ingesting raw or partially cooked shellfish within 3 months prior to onset of illness compared to none from the 17 acute hepatitis E cases (p>0.1). (Table 3.20)
( ) Imported cases included in the total
Table 3.20Association between shellfish consumption
and hepatitis A & E, 2003
Hepatitis A
Hepatitis E
Yes
4
0
Consumption of raw and partially-cooked shellfish within past three months
%
7.3
0.0
No
51 (39)
17 (9)
%
92.7
100.0
Total
55 (39)
17 (9)
LISTERIOSISThe causative agent, Listeria monocytogenes, is a gram-positive rod shaped bacterium found in soil, water, mud and silage. The mode of transmission is via ingestion of raw or contaminated milk, soft cheeses, vegetables, and ready-to-eat meats, such as pâté.
There were two laboratory reported cases of listeriosis in 2003. Both cases were in elderly adults where Listeria monocytogenes was isolated from cerebrospinal fluid.
The normal host who acquires listeriosis may experience only an acute mild febrile illness. But in pregnant women, the infection can be transmitted to the foetus and result in abortion or severe illness in the newborn. In newborns and some adults, listeriosis may manifest as meningoencephalitis and or septicaemia. In others such as the immunocompromised or elderly the infection may be subacute.
SALMONELLOSISSalmonellosis is a bacterial disease commonly presenting as acute enterocolitis, with sudden onset of fever, headache, abdominal pain, diarrhoea, nausea and sometimes vomiting. Dehydration occurs commonly in infants. The causative agent, Salmonella is a genus of gram-negative, facultative anaerobic motile rod-shape bacteria. It is a complex genus with several different systems of classification. Salmonella is grouped into subgenera and species based on biochemical and antigenic reactions. Salmonella is confirmed and identified with A-E typing. Numerous serotypes of Salmonella are pathogenic for both animals and human; that includes the most commonly reported Salmonella enterica serovar Typhimurium (S. Typhimurium) and Salmonella enterica serovar Enteritidis (S. Enteritidis).
A wide range of domestic and wild animals including poultry, swine, cattle, rodents and pets may act as a reservoir for Salmonellosis.
The mode of transmission is by ingestion of the organisms in food from infected animals or contaminated by faeces of an infected animal or person.
There were 192 cases of non-typhoid Salmonellosis, reported in 2003. Of these 97 cases were caused by Salmonella enteritidis. (Table 3.21) The incidence was highest in children below five years of age. Among the major ethnic groups, the incidence rate was highest among Malay residents. (Table 3.22 & 3.23)
58
Communicable Diseases Surveillance in Singapore 2003
Table 3.21Incidence of reported non-typhoid salmonellosis, 2003
Salmonella Species
Group B Typhimurium Non-Typhimurium
Group C
Group D Enteritidis Non-Enteritidis
Group E
Others
Total
Incidence rateper 100,000 population*
0.020.5
0.6
2.30.4
0.5
0.1
4.6
No. of cases (%)
1 (0.5)23 (12.0)
27 (14.0)
97 (50.5)18 (9.4)
23 (12.0)
3 (1.6)
192 (100.0)
Table 3.23Ethnic-gender distribution and ethnic-specific incidence rates of reported Salmonella enteritidis, 2003
*Rates are based on 2003 estimated mid-year population. (Source: Singapore Department of Statistics)
Singapore Resident
Chinese
Malay
Indian
Others
Foreigner
Total
Total (%)
67 (69.1)
19 (19.6)
4 (4.1)
2 (2.1)
5 (5.1)
97 (100.0)
Incidence rateper 100,000 population*
2.6
4.0
1.4
3.4
0.7
2.3
Table 3.22Age-gender distribution and age-specific incidence rates of reported Salmonella enteritidis, 2003
Male
10
2
2
10
9
6
11
50
Age (Yrs)
0 – 4
5 – 14
15 – 24
25 – 34
35 – 44
45 – 54
55+
Total
Total (%)
22 (22.7)
3 (3.1)
5 (5.1)
13 (13.4)
16 (16.5)
15 (15.5)
23 (23.7)
97 (100.0)
Female
12
1
3
3
7
9
12
47
Incidence rateper 100,000 population*
10.2
0.6
0.8
1.5
2.1
2.6
3.8
2.3
* Rates are based on estimated mid-year population, 2003(Source: Singapore Department of Statistics)
Female
31
10
3
2
1
47
Male
36
9
1
-
4
50
59
Table 3.25Ethnic-gender distribution and ethnic-specific incidence rates of reported shigellosis, 2003
* Rates are based on estimated mid-year population, 2003(Source: Singapore Department of Statistics)
Singapore Resident
Chinese
Malay
Indian
Others
Foreigner
Total
Total (%)
3 (75.0)
0 (0.0)
0 (0.0)
0 (0.0)
1 (25.0)
4 (100.0)
Incidence rateper 100,000 population*
0.1
0.0
0.0
0.0
0.1
0.1
SHIGELLOSISShigellosis is an acute bacterial disease involving the large and distal small intestines, characterised by fever, diarrhoea, nausea and sometimes vomiting, cramps and tenesmus. The causative agent is genus Shigella comprising of four species or serogroups namely Group A, S. dysenteriae; Group B, S. flexneri; Group C, S. boydii; and Group D, S. sonnei. Groups A, B and C, and D are further divided into 12, 14, and 18 serotypes and subtypes, respectively. The mode of transmission is mainly by direct or indirect faecal oral transmission from a symptomatic patient or a short-term asymptomatic carrier. It may also be
transmitted via water and milk due to direct faecal contamination.
A total of 4 sporadic cases of shigellosis caused by Shigella sonnei (50%), Shigella boydii (25%) and Shigella flexneri (25%) were reported in 2003. All Shigella isolates were from stool specimens. The age-gender distribution and age-specific incidence rates are shown in Table 3.24. The male to female ratio was 2:1. The ethnic-gender distribution and ethnic-specific incidence rates are detailed in Table 3.25. No deaths were reported.
Male
0
1
0
1
0
0
0
2
Age (Yrs)
0 – 4
5 – 14
15 – 24
25 – 34
35 – 44
45 – 54
55+
Total
Total (%)
1(25.0)
2 (50.0)
0 (0.0)
1 (25.0)
0 (0.0)
0 (0.0)
0 (0.0)
4 (100.0)
Female
1
1
0
0
0
0
0
2
Incidence rateper 100,000 population*
0.5
0.4
0.0
0.1
0.0
0.0
0.0
0.1
Table 3.24Age-gender distribution and age-specific incidence rates of reported shigellosis, 2003
* Rates are based on estimated mid-year population, 2003(Source: Singapore Department of Statistics)
Female
1
0
0
0
1
2
Male
2
0
0
0
0
2
60
Communicable Diseases Surveillance in Singapore 2003
FOOD POISONINGIn 2003, there were 199 notifications of food poisoning involving 1,517 cases, compared with 238 notifications involving 2,247 cases in 2002. (Figure 3.7) Of these, 145
notifications were classified as outbreaks. An outbreak is defined as two or more cases epidemiologically linked to a common source.
Year
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
0
50
100
150
200
250
300
Cases Notifications
1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003
Notification of food poisoning, 1966 - 2003 Figure 3.7
61
No.
of c
ases
No.
of n
otifi
catio
ns
The majority of the outbreaks (80.7%) originated in restaurants and eating houses. (Table 3.26) The primary contributing factors of the 145 outbreaks
were due to poor personal, food and environmental hygiene.
Table 3.26Food poisoning notifications by type of food establishment, 2003
Type of food establishments
Restaurant In hotels Others
Eating house
Hawker center NEA / ENV HDB
Private food court
Fast food outlets
Other food outlets
Fair Food fair
Canteens Factory/office/staff/construction site School
Supermarket/market shops
Catering (licensed)
In house kitchen within institutions Police Drug rehabilitation centre Others
Total
No. of cases
192617
166
63
15
20
16
66
4185
6
83
1587
36
1,517
Microbiological investigations of 265 food samples and eight environmental swabs were conducted. Thirteen were positive for Staphylococcus aureus; seven E.coli; two Vibrio parahaemolyticus, one
Bacillus cereus, and one Salmonella organism. Of 190 food handlers sent for screening, five were found to be positive for Salmonella organisms, and one was positive for V. parahaemolyticus.
(*) 2 or more epidemiologically linked cases involved
Notifications Classifiedas Outbreak (*)
1558
42
21
3
2
5
2
23
1
4
11 3
145
No. of notifications
16 69
64
4 2
11
3
8
2
2 4
5
4
11 3
199
62
Communicable Diseases Surveillance in Singapore 2003
Norovirus Outbreak
Between December 2003 and January 2004, a total of 14 oyster-associated gastroenteritis outbreaks involving 305 people were notified from the central, eastern and northern regions of Singapore. An epidemiological investigation and case control study was carried out for each outbreak to establish the mode of transmission.
Of 305 cases (21.7%) identified from 1408 persons interviewed, 73% were males. The median age was 29 years (range 6–77 years). The ethnic distribution of the cases was Chinese, 93.7%; Malays, 5.8%; and Indians, 0.4%. The clinical symptoms were diarrhoea (94%), abdominal cramps (72%), vomiting (69%), fever (54%) and headache (49%). More than half of the cases (52.8%) sought medical treatment and 12.8% were hospitalised. The others self-medicated. No pathogenic enterobacter were isolated from stool samples of those hospitalised. Most cases recovered within two to three days and the median incubation period was 29 hours (range 3–103 hours). The onset of illness of the reported cases is shown in Figure 3.8. Analyses of
the food-specific attack rates based on 223 cases and 209 controls in six of the outbreaks showed that consumption of raw half-shelled oysters was significantly associated with illness in each outbreak (p< 0.0001). (Table 3.27)
10
20
30
40
50
60
0
14-D
ec-0
3
15-D
ec-0
3
16-D
ec-0
317
-Dec
-03
18-D
ec-0
3
19-D
ec-0
3
20-D
ec-0
321
-Dec
-03
22-D
ec-0
3
23-D
ec-0
324
-Dec
-03
25-D
ec-0
326
-Dec
-03
27-D
ec-0
3
28-D
ec-0
3
29-D
ec-0
3
30-D
ec-0
3
31-D
ec-0
3
Date of onset
No.
of c
ases
(n=2
23)
Onset of symptoms of
oyster-associated gastroenteritis
01-J
an-0
4
02-J
an-0
4Location
Restaurant 1
Restaurant 2
Residence 1
Restaurant 3
Military Institution 1
Restaurant 4
Outbreak
1.
2.
3.
4.
5.
6.
Attack rate (%)
82.9
95.8
88.9
82.4
98.8
93.8
Table 3.27 Association between oyster consumption and illness in 6 outbreaks of gastroenteritis
* Fisher’s exact test
ill
63
23
16
14
82
15
well
13
1
2
3
1
1
Ate
ill
6
0
1
1
4
1
well
72
17
10
30
47
13
Did not eat Attack rate (%)
7.7
0.0
9.1
3.2
7.8
7.1
OR
10.8
-
9.8
25.5
12.6
13.1
P value*
< 0.0001
< 0.0001
< 0.0001
< 0.0001
< 0.0001
< 0.0001
Figure 3.8
63
62
Site investigation revealed there was no departure from good food hygiene practices at the various implicated food establishments. None of the food handlers had a recent history of gastroenteritis.
The frozen half-shelled oysters (Crassostrea virginica) were traced to a specific shipment (11.4 tonnes) imported from Shandong, China. All remaining 21 cartons distributed to four seafood suppliers were voluntarily recalled by the importer. The recalled shipment implicated in the outbreak was tested for bacterial enteropathogens, norovirus and rotavirus at the Veterinary Public Health Laboratory, Agri-Food and Veterinary Authority of Singapore. RT-PCR revealed
that nine of 12 samples tested were positive for norovirus. RT-PCR sample was also sent to the Institute of Environmental Science & Research Ltd, New Zealand for reference testing, and confirmed positive for norovirus. Electromicroscopic (EM) examination was performed at the National University of Singapore and norovirus-like viral particles (35-50nm) were identified. In addition, 4 of the 5 stool samples tested positive for norovirus group II RNA at the Defence Medical and Environmental Research Institute (DMERI) laboratory.
The oyster-associated outbreak ceased after the remaining supply of the shipment was recalled.
64
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