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Communicable Diseases Surveillance in Singapore 2009

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IIIFood-/Water-Borne Diseases

Food-borne diseases are caused by the ingestion of foodstuffs or water contaminated by toxins associated with bacterial growth in the food, bacterial, viral or parasitic agents, toxins produced by harmful algal species or present in specific fish species or heavymetals and other organic compounds.

ACUte DIARRHoeAL ILLnessesTherewereatotalof107,953attendancesatpolyclinicsfor acute diarrhoeal illnesses in 2009 - a marginal decreaseof0.2%overthe108,184seenin2008.Weeklysurveillance of acute diarrhoeal attendances showed a similar pattern to that of previous year (Figure 3.1).

Figure 3.1Weekly attendances of diarrhoeal illnesses at polyclinics, 2008 – 2009

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, Campylobacter coli are the usual causes of Campylobacter enteritis in humans. The mode of transmission is by ingestion of the organism in undercooked chicken and pork, contaminated food and water or unpasteurised milk.A total of 261 cases of Campylobacter enteritis were reportedin2009,anincreaseof47.5%incomparisonto177casesreportedin2008.Campylobacter jejuni was

isolated in majority of the cases (Table 3.1). Of the 261 reportedcases,253werelocalresidentscomprising27imported cases and 226 indigenous cases. The other 8 cases were foreigners who came to Singapore to seek medical treatment for infections acquired overseas.

The incidence rate among indigenous cases was highest in the 0-4 year age group, with an overall male to female ratio of 1.5:1 (Table 3.2). Among the three major ethnic groups, the Chinese ethnic group had the highest incidence followed by Indians and Malays (Table 3.3).

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table 3.1Incidence of reported Campylobacter enteritis, 1998 – 2009

yearno. of cases caused by Incidence rate per

100,000 population*C. jejuni C. coli C. laridis other species total

1998 254 0 4 11 269 6.91999 323 0 3 17 343 8.72000 226 0 1 4 231 5.82001 105 0 0 0 105 2.52002 50 0 0 0 50 1.22003 140 1 0 3 144 3.42004 122 2 0 7 131 3.12005 241 0 0 0 241 5.52006 227 0 0 9 236 5.3

2007 161^ 1^ 0 9 170 3.7

2008 158 0 0 19 177 3.7

2009 240 0 0 21 261 5.2

^ one case has a concurrent infection of both C.jejuni and C.coli*Rates are based on 2009 estimated mid-year population.

(source: singapore Department of statistics)

table 3.2Age-gender distribution and age-specific incidence rates of reported Campylobacter enteritis^, 2009

Age (yrs) male Female total (%) Incidence rate per 100,000 population*

0 – 4 92 50 142 (56.1) 65.65 – 14 33 29 62 (24.5) 12.3

15 – 24 7 4 11 (4.3) 1.425 – 34 3 6 9 (3.6) 0.835 – 44 4 3 7(2.8) 0.845 – 54 5 2 7(2.8) 1.055+ 6 9 15 (5.9) 1.8

total 150 103 253 (100) 5.1

^ excluding eight foreigners seeking medical treatment in singapore.*Rates are based on 2009 estimated mid-year population.


table 3.3Ethnic-gender distribution and ethnic-specific incidence rates of reported Campylobacter enteritis^, 2009

male Female total (%) Incidence rate per 100,000 population*

Singapore ResidentChinese 80 54 134 (53.1) 4.8Malay 7 11 18(7.1) 3.6Indian 9 4 13 (5.1) 3.8Others 20 13 33 (13.0) 27.5

Foreigner 34 21 55(21.7) 4.4

total 150 103 253 (100) 5.1

^ excluding eight foreigners seeking medical treatment in singapore* Rates are based on 2009 estimated mid-year population



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CHoLeRACholera is an acute bacterial enteric disease characterising 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 canbe further classified into serotypes Inaba,Ogawa

and Hikojima. Other serogroups in addition to O1 are O139 and Non O. The mode of transmission is through ingestion of food or water contaminated with faeces or vomitus of infected persons.

In 2009, three imported and one local isolated case of cholera was reported (Figure 3.2). The overall incidence rate was 0.08 per 100,000 population (Table 3.4 and 3.5).

Figure 3.2e-weekly distribution of reported cholera cases in singapore, 2008-2009

table 3.4Age-gender distribution and age-specific incidence rates of reported cholera cases, 2009


0 – 4 0 0 0 (0.0) 0.00

5 – 14 0 0 0 (0.0) 0.00

15 – 24 0 0 0 (0.0) 0.00

25 – 34 1 0 1 (25.0) 0.09

35 – 44 1 0 1 (25.0) 0.11

45 – 54 1 0 1 (25.0) 0.14

55+ 1 0 1 (25.0) 0.12

total 4 0 4 (100.0) 0.08

*Rates are based on 2009 estimated mid-year population.(source: singapore Department of statistics)

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table 3.5Ethnic-gender distribution and ethnic-specific incidence rates of reported cholera cases, 2009


Singapore Resident

Chinese 2 0 2 (50.0) 0.07

Malay 1 0 1 (25.0) 0.20

Indian 1 0 1 (25.0) 0.29

Others 0 0 0 (0.0) 0.00

Foreigner 0 0 0 (0.0) 0.00

total 4 0 4 (100.0) 0.08

*Rates are based on 2009 estimated mid year population(source: singapore Department of statistics)

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 and non-productive cough (in the early stage of the illness). Constipation is more common than diarrhoea in adults. It is important to appreciate the difference between Salmonellosis food poisoning, and typhoid or paratyphoid fever, commonly known as enteric

fevers. Causative organisms for the enteric fevers are Salmonella typhi and Salmonella paratyphi (types A, B or C) and infections are usually associated with travel to countries where these diseases are endemic.

During the period 2005 to 2009, a total of 488 cases of entericfeverwerereported,ofwhich349(71.5%)casesweretyphoidand139(28.5%)caseswereparatyphoid.Themajority(92.2%)wereimportedcases(Table3.6).

table 3.6Classification of reported enteric fever cases, 2005 – 2009

year typhoidParatyphoid

totalA B C

2005 69 (64) 24 (23) 2 (1) 0 95 (88)

2006 60 (55) 23 (23) 0 0 83(78)

2007 67(63) 28 (25) 5 (2) 0 100 (90)

2008 84 (84) 28(27) 1 (0) 0 113 (111)

2009 69 (62) 21 (19) 7(3) 0 97(83)

total 349 (328) 124 (116) 15 (6) 0 488 (450)

( ) imported cases

In2009,atotalof97casesofentericfevers,comprising69 cases of typhoid, and 21 cases of paratyphoid A and 7 cases of paratyphoid B were reported, a decrease

from 113 cases of enteric fevers reported in 2008 (Figure 3.3).


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Figure 3.3e-weekly distribution of reported enteric fever cases, 2008 – 2009

table 3.7Classification of reported typhoid and paratyphoid cases, 2009

Population group typhoid no. (%) Paratyphoid no. (%)

Local residents 20 (29.0) 18 (64.3)

Foreigners seeking medical treatment in Singapore 6(8.7) 4 (14.3)

Tourists 5(7.2) 2(7.1)

Other categories of foreigners 38 (55.1) 4 (14.3)

total 69 (100.0) 28 (100.0)

typhoid FeverOf the 69 reported cases of typhoid, 62 were imported. Of the 62 imported cases, 11 were Singapore residents, 36 were work permit or employment pass holders, four were student pass holders, six foreigners seeking treatment inSingaporeandfivetourists(Table3.7).Ofthesevenlocal cases, four were Singapore residents while three were work permit or employment pass holders.

Overall the incidence rate of typhoid fever among local residents was 1.2 per 100,000 population (Table 3.8).

The incidence rate among local residents was highest in the 15 – 24 years age group, followed by the 25 – 34 years age group.

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table 3.8Age-gender distribution and age-specific incidence rates of reported typhoid cases^, 2009


0 – 4 2 0 2 (3.4) 0.9

5 – 14 2 1 3 (5.2) 0.6

15 – 24 9 13 22(37.9) 2.8

25 – 34 9 11 20 (34.5) 1.9

35 – 44 5 1 6 (10.3) 0.7

45 – 54 3 0 3 (5.2) 0.4

55 – 64 0 1 1(1.7) 0.2

65+ 0 1 1(1.7) 0.3

total 30 28 58 (100.0) 1.2

^ Excluding six foreigners seeking medical treatment in Singapore and five tourists*Rates are based on 2009 estimated mid-year population.


Among the three major ethnic groups, Indians had the highest incidence rate followed by Malays (Table 3.9).

Foreignerscomprised67.2%ofthecases.

table 3.9Ethnic-gender distribution and ethnic-specific incidence rates of reported typhoid cases^, 2009


Singapore Resident

Chinese 4 5 9 (15.5) 0.3

Malay 1 1 2 (3.4) 0.4

Indian 3 1 4 (6.9) 1.2

Others 1 3 4 ( 6.9) 3.3

Foreigner 21 18 39(67.2) 3.1

total 30 28 58 (100.0) 1.2

^ Excluding six foreigners seeking medical treatment in Singapore and five tourists*Rates are based on 2009 estimated mid-year population.


Of the 11 Singapore residents who acquired the infection overseas, the majority contracted the disease from India

and Indonesia (Table 3.10). Most cases were overseas onvacation(81.2%)(Table3.11).


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table 3.10singapore residents who contracted typhoid overseas by country of origin, 2005 – 2009

Classification2005 2006 2007 2008 2009

no. (%) no. (%) no. (%) no. (%) no. (%)Country visited

Bangladesh 1 (3.8) 1 (8.3) 1 (6.3) 2 (6.3) 0 (0.0)Cambodia 1 (3.8) 0 (0.0) 0 (0.0) 0 (0.0) 2 (18.2)China 0 (0.0) 0 (0.0) 0 (0.0) 1 (3.1) 0 (0.0)India 13 (50.0) 6 (50.0) 8 (50.0) 19 (59.4) 3(27.3)Indonesia 6 (23.1) 4 (33.4) 4 (25.0) 5 (15.6) 3(27.3)Malaysia 3 (11.5) 1 (8.3) 2 (12.4) 4 (12.5) 1 (9.1)Myanmar 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)Nepal 1 (3.8) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)Qatar 0 (0.0) 0 (0.0) 0 (0.0) 1 (3.1) 0 (0.0)Thailand 1 (3.8) 0 (0.0) 1 (6.3) 0 (0.0) 2 (18.2)

total 26 (100.0) 12 (100.0) 16 (100.0) 32 (100.0) 11 (100.0)

table 3.11singapore residents who contracted typhoid overseas by purpose of travel 2005 – 2009

Classification2005 2006 2007 2008 2009

no. (%) no. (%) no. (%) no. (%) no. (%)Purpose of travel

Vacation 22 (84.6) 8 (66.8) 12(75.0) 29 (90.6) 9 (81.2)

Business/employment 3 (11.5) 2 (16.6) 3(18.7) 3 (9.4) 2 (18.2)

Pilgrimage 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)

Others 1 (3.9) 2 (16.6) 1 (6.3) 0 (0.0) 0 (0.0)

total 26 (100.0) 12 (100.0) 16 (100.0) 32 (100.0) 11 (100.0)

Paratyphoid FeverOf the 28 reported cases of paratyphoid, 22 were imported cases and six were indigenous cases. Of the 22 imported cases, eleven were Singapore residents, four were work permit holders and one was a student pass holder. The remaining six were foreigners including two tourists not residing in Singapore, and those who came

to seek treatment in Singapore. The overall incidence rate of paratyphoid fever among local residents was 0.4 per 100,000 population (Table 3.12).

The incidence rate among local residents was highest in the 25 – 34 years age group (Table 3.12).

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table 3.12Age-gender distribution and age-specific incidence rates of reported paratyphoid cases^, 2009


0 – 4 0 0 0 (0.0) 0.0

5 – 14 1 0 1 (4.5) 0.2

15 – 24 0 2 2 (9.1) 0.3

25 – 34 6 2 8 (36.4) 0.7

35 – 44 2 2 4 (18.2) 0.5

45 – 54 2 0 2 (9.1) 0.3

55 - 64 0 2 2 (9.1) 0.4

65+ 2 1 3 (13.6) 0.8

total 13 9 22 (100.0) 0.4

^ excluding two tourists and four foreigners seeking medical treatment in singapore *Rates are based on 2009 estimated mid-year population.


Among the three major ethnic groups, Indians had the highest incidence rate (0.6 per 100,000 population) in

2009(Table3.13).Foreignerscomprised18.2%ofthecases.

table 3.13Ethnic-gender distribution and ethnic-specific incidence rates of reported paratyphoid cases^, 2009


Singapore Resident

Chinese 6 4 10 (45.5) 0.4

Malay 0 1 1 (4.5) 0.2

Indian 1 1 2 (9.1) 0.6

Others 3 2 5(22.7) 4.2

Foreigner 3 1 4 (18.2) 0.3

total 13 9 22 (100.0) 0.4

^ excluding two tourists and four foreigners seeking medical treatment in singapore *Rates are based on 2009 estimated mid-year population.


Of the eleven Singapore residents who acquired the infection overseas, the majority contracted the disease from India (4) and Indonesia (3) with rest from China

(1),Malaysia (1), Myanmar (1) and Pakistan (1) (Table 3.14).Mostcaseswere travellingonvacation(81.8%)(Table 3.15).


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table 3.14singapore residents who contracted paratyphoid overseas by country of origin, 2005 – 2009

Classification2005 2006 2007 2008 2009

no. (%) no (%) no (%) no (%) no (%)Country visited

Australia 0 (0.0) 1 (20.0) 0 (0.0) 0 (0.0) 0 (0.0)

Bangladesh 0 (0.0) 0 (0.0) 1 (11.1) 0 (0.0) 0 (0.0)

China 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 1(9.1)

Hong Kong 1 (14.3) 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0)

India 2 (28.6) 2 (40.0) 4 (44.4) 2 (22.2) 4 (36.4)

Indonesia 2 (28.6) 1 (20.0) 0 (0.0) 5 (55.6) 3(27.3)

Malaysia 2 (28.6) 0 (0.0) 2 (22.2) 1 (11.1) 1 (9.1)

Myanmar 0 (0.0) 1 (20.0) 1 (11.1) 0 (0.0) 1 (9.1)

Pakistan 0 (0.0) 0 (0.0) 0 (0.0) 0 (0.0) 1 (9.1)

Thailand 0 (0.0) 0 (0.0) 1 (11.1) 1 (11.1) 0 (0.0)

total 7 (100.0) 5 (100.0) 9 (100.0) 9 (100.0) 11 (100.0)

table 3.15singapore residents who contracted paratyphoid overseas by purposes of travel, 2005 – 2009

Classification2005 2006 2007 2008 2009

no. (%) no (%) no (%) no (%) no (%)

Purpose of travel

Vacation 6(85.7) 4 (80.0) 6(66.7) 7(77.8) 9 (81.8)

Business/employment 1 (14.3) 1 (20.0) 2 (22.2) 2 ( 22.2) 2 (18.2)

Seminar 0 (0.0) 0 (0.0 ) 1 (11.1) 0 (0.0 ) 0 (0.0)

total 7 (100.0) 5 (100.0) 9 (100.0) 9 (100.0) 11 (100.0)

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 faecal contaminated drinking water.

There were 89 cases of serologically confirmed viralhepatitis A and 90 cases of viral hepatitis E reported ascompared to107casesand54cases respectivelyin 2008 (Figures 3.4 and 3.5). Of the total reported, six cases of viral hepatitis A and nine cases of viral hepatitis E involved patients seeking medical treatment in Singapore (Table 3.16).

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Figure 3.4e-weekly distribution of reported hepatitis A cases, 2008 – 2009

Figure 3.5e-weekly distribution of reported hepatitis e cases, 2008 – 2009

num

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umbe

r of C

ases

table 3.16Classification of reported acute viral hepatitis A & E cases, 2009

Population groupno. of cases

Hepatitis A (%) Hepatitis e (%)

Local residents 55 (61.8) 43(47.8)

Workpermitholders/otherforeigners 28 (31.5) 38 (42.2)

Foreigners seeking medical treatment in Singapore 6(6.7) 9 (10.0)

total 89 (100.0) 90 (100.0)

Among local residents, theage-specific incidencerateof acute hepatitis A (2.3 per 100,000 population) was highest in the 25 – 34 years age group and Hepatitis E(2.5per100,000population)washighest inthe65+

years age group. The overall male to female ratio was 2.0:1 for acute hepatitis A and 2.0:1 for acute hepatitis E(Table3.17).


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table 3.17Age-gender distribution and age-specific incidence rates of acute hepatitis A & E^, 2009

Age (yrs)

Hepatitis A Hepatitis e

male Female total (%) Incidence rate per 100,000 population* male Female total (%) Incidence rate per

100,000 population*

0 – 4 0 2 2 (2.4) 0.9 0 0 0 (0.0) 0.0

5 – 14 6 4 10 (12.2) 2.0 2 0 2 (2.5) 0.4

15 – 24 10 4 14(17.1) 1.8 15 1 16 (20.3) 2.0

25 – 34 14 11 25 (30.5) 2.3 11 2 13 (16.5) 1.2

35 – 44 6 4 10 (12.2) 1.1 10 9 19 (24.0) 2.2

45 – 54 11 2 13 (15.8) 1.9 8 6 14(17.7) 2.0

55 – 64 4 0 4 (4.9) 0.9 4 2 6(7.6) 1.3

65+ 4 0 4 (4.9) 1.1 3 6 9 (11.4) 2.5

total 55 27 82 (100.0) 1.6 53 26 79 (100.0) 1.6

^excluding six cases of foreigners and one tourist seeking medical treatment in singapore (hepatitis A) and nine cases of foreigners and two tourists seeking medical treatment in singapore (hepatitis e)


Of the three main ethnic groups, Indians had the highest incidence rate of hepatitis A while Chinese has the highest incidence of hepatitis E. The ethnic and gender

distribution of Hepatitis A and E are shown in Table 3.18.

table 3.18Ethnic-gender distribution and ethnic-specific incidence rates of acute hepatitis A & E^, 2009


male Female total (%)Incidence rate

per 100,000 population*

male Female total (%)Incidence rate

per 100,000 population*

Singapore ResidentChinese 25 10 35(42.7) 1.3 18 19 37(46.8) 1.3Malay 5 2 7(8.5) 1.4 2 0 2 (2.5) 0.4Indian 4 2 6(7.3) 1.7 2 1 3 (3.8) 0.9Others 4 3 7(8.5) 5.8 0 1 1 (1.3) 0.8

Foreigner 17 10 27(33.0) 2.2 31 5 36 (45.6) 2.9total 55 27 82 (100.0) 1.6 53 26 79 (100.0) 1.6

^excluding six cases of foreigners and one tourist seeking medical treatment in singapore (hepatitis A) and nine cases of foreigners and two tourists seeking medical treatment in singapore (hepatitis e)


overseas-acquired viral hepatitisOf the 89 cases of hepatitis A and 90 cases of hepatitis E,52(58.4%)and45(50.0%)casesrespectivelywereacquired overseas (Table 3.19). The majority of cases

acquired the infection from the Indian subcontinent (53.6%)andSoutheastAsia(38.3%)(Table3.20).

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table 3.19overseas-acquired acute hepatitis A & e by population group, 2009

Population group

no. of casestotal (%)


Local ResidentsResidents who contracted the disease overseas 29 10 39 (40.2)Workpermit/employmentpassholders 8 24 32 (33.0)Student pass holders 8 0 8 (8.2)

Foreigners seeking medical treatment 7 11 18 (18.6)total 52 45 97 (100.0)

table 3.20overseas-acquired acute hepatitis A & e by country of origin, 2009

Country visitedno. of cases

total (%)Hepatitis A Hepatitis e

Southeast AsiaIndonesia 15 3 18 (18.6)Vietnam 1 1 2 (2.1)Malaysia 6 1 7(7.3)Philippines 2 1 3 (3.1)Myanmar 1 0 1 (1.0)Thailand 5 0 5 (5.2)Cambodia 1 0 1 (1.0)

Indian SubcontinentBangladesh 3 25 28 (28.9)India 13 8 21(21.7)Nepal 1 0 1 (1.0)Maldives 0 1 1 (1.0)Sri Lanka 0 1 1 (1.0)

Other CountriesColumbia 1 0 1 (1.0)China 1 2 3 (3.1)Hong Kong SAR 0 1 1 (1.0)South Korea 0 1 1 (1.0)Syria 1 0 1 (1.0)Uzbekistan 1 0 1 (1.0)

total 52 45 97 (100.0)

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 and the elderly. The causative pathogen, Salmonella is a genus of gram-negative, facultative anaerobic motile rod-shape bacteria. It is divided into two

species, Salmonella enterica and Salmonella bongori. Salmonella enterica is further subdivided into subspecies and serotypes based on biochemical and antigenic reactions.Themajority(59%)ofSalmonella serotypes belong to S. enterica subsp. enterica. Within S. enterica subsp. enterica, the most common O-antigen serogroups identified are from A to E. Numerous serotypes of


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Salmonellaarepathogenicforbothanimalsandhuman;that includes the most commonly reported Salmonella enterica serovar Typhimurium (S. Typhimurium) and Salmonella enterica serovar Enteritidis (S. Enteritidis).

Poultry is the commonest source of human salmonellosis. Consumption of contaminated meat and eggs is also a frequent cause. A wide range of domestic and wild

animals including poultry, swine, cattle, rodents and pets may act as reservoirs for salmonellosis.

A total of 1144 laboratory-confirmed cases of non-typhoidal salmonellosis were reported in 2009, an increase of 1.6-fold from 718 cases reported in 2008(Figure 3.6). Of these, 264 cases were caused by S. Enteritidis (Table 3.21).

Figure 3.6e-weekly distribution of reported salmonellosis cases, 2008 – 2009

table 3.21Incidence of reported non-typhoidal salmonellosis, 2009

salmonella serotypes no. of cases (%) Incidence rate per100,000 population*

Group A 1 (0.1) 0.02

Group B

Typhimurium 15 (1.3) 0.3

Untyped 288 (25.2) 5.8

Group C 184 (16.1) 3.7

Group D

Enteritidis 264 (23.1) 5.3

Untyped 223 (19.5) 4.5

Group E 111(9.7) 2.2

Group G 3 (0.3) 0.1

Untyped 55 (4.8) 1.1

total 1144 (100.0) 22.9


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s. enteritidis Of the 264 cases reported in 2009, 255 were local residents comprising 9 imported and 246 indigenous cases. Nine cases of S. Enteritidis were foreigners seeking medical treatment in Singapore.

ThenotificationsofS.Enteritidisamonglocalresidentshaddecreasedby6.6%ascompared to273cases in2008. The incidence rate was highest for the age group 0 - 4 years (Table 3.22).

table 3.22Age-gender distribution and age-specific incidence rates of reported S. Enteritidis^, 2009


0 – 4 33 27 60 (23.5) 27.7

5 – 14 2 1 3 ( 1.3) 0.6

15 – 24 12 9 21 ( 8.2) 2.6

25 – 34 20 13 33 (12.9) 3.1

35 – 44 16 7 23 ( 9.0) 2.6

45 – 54 20 9 29 ( 11.4) 4.2

55 - 64 16 12 28 ( 11.0) 6.2

65+ 28 30 58(22.7) 15.9

total 147 108 255 (100.0) 5.1

^ excluding one tourist and eight foreigners seeking medical treatment in singapore*Rates are based on 2009 estimated mid-year population.


Among the three major ethnic groups, Indians had the highest incidence rate of S. Enteritidis followed by

Malays and Chinese (Table 3.23).

table 3.23Ethnic-gender distribution and ethnic-specific incidence rates of reported S. Enteritidis^, 2009


Singapore Resident Chinese 64 72 136 ( 53.3) 4.9 Malay 16 18 34 ( 13.3) 6.8 Indian 9 15 24 ( 9.4) 7.0 Others 3 3 6 ( 2.4) 5.0

Foreigner 16 39 55 ( 21.6) 4.4total 108 147 255 (100.0) 5.1

^ excluding one tourist and eight foreigners seeking medical treatment in singapore*Rates are based on 2009 estimated mid-year population.



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FooD PoIsonIngTherewere211notificationsoffoodpoisoninginvolving1549cases,comparedwith136notifications involving1252 cases in 2008 (Figure 3.7). Of these, 201

notificationswereclassifiedasoutbreaksinvolvingtwoor more cases epidemiologically linked to a common source,ascomparedto126notificationsin2008.

Figure 3.7Notifications of food poisoning in Singapore, 1965-2009

Majority(52.7%)oftheoutbreaksoccurredinrestaurantandeatinghouses.(Table3.26).

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table 3.26food poisoning notifications by type of food establishment, 2009

type of food establishments No. of notifications Notification classified as outbreak*

no of food establishments

involvedno. of cases

general outletsRestaurant

In hotels 12 12 11 68Others 66 62 59 211

Eating house 35 32 35 122Hawker centre 24 23 16 206Private food court 12 11 11 29Fast food outlets 9 9 9 26Other food outlets 17 16 14 101Canteens

Factory/office/staff/constructionsite 1 1 1 15

School 2 2 2 9Supermarket/marketshops 3 3 3 8Catering (licensed) 12 12 11 306Catering (unlicensed) 4 4 4 76Food factory 0 0 0 0sub-total (general outlets) 197 187 176 1177InstitutionIn house kitchen

Army 1 1 1 16DRC 1 1 1 124School 2 2 1 171Hostel/Hotel 4 4 4 35Others 6 6 6 26

sub-total (Institution) 14 14 13 372total 211 201 189 1549

*two or more epidemiologically linked cases involved

Microbiological investigations of 212 food samples and 30 environmental swabs were conducted. Of the 212 food samples, three were positive for Staphylococcus aureus, one was positive for Vibrio parahaemolyticus, one was positive for Bacillus cereus and one was positive for Escherichia coli. Of 385 food handlers sent for screening, 14 were found to be positive for Salmonella, six were positive for Aeromonas, four were positive for Plesiomonas shigelloides, three were positive for Campylobacter, one was positive for Salmonella Typhi and Vibrio parahaemolyticus each, while another four were positive for Norovirus and Rotavirus respectively.

One case study is discussed below.

Case study 1: Food poisoning outbreak associated with serving of reheated turkey - a retrospective cohort study.

NotificationOn 22 Dec 2009, the Ministry of Health (MOH) was notifiedof71peoplesufferingfromfoodpoisoningaftera Christmas party held in a hospital on 18 Dec 2009. The report summarises the investigation into this outbreak which implicates reheated turkey as the source of the outbreak.


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Epidemiological findingsAcasewasdefinedasapersonwhodevelopeddiarrhoeaor vomiting after attending the Christmas party on 18 Dec 2009.67caseswereidentifiedbasedonthisdefinitionfrom 182 attendees. Cases were mostly Singaporean Chinese(n=38;56.7%),female(n=47;70.1%),agedbetween25and34years (n=37;56.1%).Diarrhoeaand stomach cramps were the dominant symptoms of this outbreak with 41 (61.2%) cases self-medicatingand the remainder seeking private outpatient treatment (table 1).

Based on data from 56 cases who could provide an exact time to their onset of illness, a mean and median incubation period of 40 hours, with range from 9 – 109 hours was calculated. The epidemiological curve (Figure 1) shows a normal distribution with a single peak at 0800 hours on 20 Dec 09.

The source of the outbreak was traced to a catering company who was in charge of the event. A total of eight food samples, an environmental swab and 10 food handlers from this caterer were tested. High total plate count and coliform counts were found in various foods (table 2). One food handler was positive for norovirus group II.

As the cohort of individuals attending the party was well defined, a retrospective cohort study was conducted.Of the 182 attendees, 128 (70.3%) responded to thequestionnaire.Food-specificriskscalculatedconcludedthat people who ate turkey were twice as likely to develop food poisoning symptoms compared to those who did not (table 3). No common foods were consumed prior to the party.

DiscussionMost of the attendees were aged between 25 to 34 years of age, with some below the age of 15 years and above the age of 55. This observation was consistent with the fact that the party was extended to the relatives of the staff.Nogender,ethnicoragespecificdifferenceswereobserved between those who were ill and well.

The onset chart shows a point source outbreak with a mean and median incubation period of 40 hours. This suggests Salmonella, Campylobacter and norovirus as possible agents of this outbreak. Long incubation periods up to 10 days are not uncommon to Salmonella and Campylobacter infections, and can occur when low

doses of the pathogen are ingested (1).Thefindingofhighcoliformcountandhigh totalplatecounts in food that has been just cooked suggests a poor level of hygiene during food processing. Consistent with laboratory findings, the implicated food premisewas penalised for poor housekeeping and stacking raw food with cooked food. As the turkey was imported at a seasonal basis from the United States, neither the caterer nor the meat wholesaler could provide any samples for testing.

This study is limited by the lack of stools from cases and samples of the implicated item to test for pathogens. Hence the report can only speculate on the agent responsible for the outbreak based on available evidence.

Turkey was found to be the implicated food item in this outbreak (RR = 2.03). To determine where the likely source of infection was, the meat wholesaler and the caterer were interviewed in greater detail.

Turkeys are processed at the meat wholesaler (Figure 2) under controlled conditions and are inspected by regulating authorities on a regular basis. After the turkey was prepared at the wholesaler, the turkey was delivered to the caterer within two hours. It is recommended the turkey be consumed within three hours of purchase or stored and reheated at 200°C. The caterers, however, reported that they had the cooked turkeys delivered to them 1 day in advance and they reheated the turkeys at 160°C for 30 minutes the next day, after which transferred the turkey to serving dishes for garnishing prior to serving.

In the context of this outbreak, the process of storing cooked food may have led to the proliferation of food borne pathogens which were not eliminated due to undercooking compounded with additional food handling (transfer and garnishing) and poor hygiene practices such as poor housekeeping and mixing of raw and cooked food.

Undercooking or reheating turkeys have been implicated in outbreaks in the United States. Undercooked turkey was responsible for an outbreak of salmonellosis at a Thanksgiving Dinner in Nevada, where raw turkey was cookedat177°Cforonehour,withouttheuseofameatthermometer, resulting in undercooked turkeys and stuffing(2).Otherturkey-relatedoutbreakssuchasone

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in the state of Kentucky, was caused by the undercooking of turkey resulting in proliferation of bacteria during the four hour post-cooking period prior to consumption (3). Reheating cooked turkey, together with ill food handlers, undercooking of raw turkeys, and leaving cooked turkey to stand for 10 hours unrefrigerated prior to serving, caused a salmonellosis outbreak in South Carolina (4).

RecommendationsTurkeys are an important source of food poisoning owing to the likelihood of the bird being undercooked or poorly handled after cooking. It is recommended to consume turkey immediately after cooking or to store andreheattheturkeyatatemperaturesufficienttokillany proliferating bacteria. Additionally, turkey and other large animals should be cooked at high temperatures and for a duration that is sufficient to ensure that themeat is cooked through.

References1. Heymann DL (2008). Control of Communicable

Diseases Manual, 19th Edition. APHA Press. 2. Centers for Disease Control and Prevention (1996).

Salmonellosis associated with a Thanksgiving dinner--Nevada, 1995. MMWR Morb Mortal Wkly Rep. 45 (46):1016-7.

3. Kelsay RC (1970). Food poisoning outbreak inKentucky traced to creamed turkey. Public Health Rep. 85 (12): 1103-8.

4. Luby SP, Jones JL, Horan JM (1993). A largesalmonellosis outbreak associated with a frequently penalized restaurant. Epidemiol Infect. 110 (1):31-9.

table 1: symptoms and mode of treatment of cases

mode of treatment (n = 67) Count (%)

Self-medicated 41 (61.2)

Outpatient 26 (38.8)

Hospitalisation 0 (0.0)

symptoms (n = 67) Count (%)

Diarrhoea 65(97.0)

Stomach cramps 59 (88.1)

Nausea 20 (29.9)

Headache 15 (22.4)

Fever 12(17.9)

Vomiting 11 (16.4)

Bloody diarrhoea 1 (1.5)

table 2: Results of bacterial analysis of food and environmental sampling of the caterer implicated in the food poisoning incident.

Food sample total plate count (count) total coliform count (count)

Green Salad with Dressing Positive(150’000CFU/g) Positive(460MPN/g)

Honey Baked Ham Positive(580’000CFU/g) Positive(240MPN/g)

Sautéed Spicy Prawn Negative(800CFU/g) Negative (not detected)

Sautéed Chipolata sausage Negative(1100CFU/g) Negative(not detected)

Vegetable medley Negative(12000CFU/g) Positive(460MPN/g)

Christmas log cake Negative(<100CFU/g) Negative(9.2MPN/g)

IceJelly Negative(1400CFU/g) Positive(1100MPN/g)

Ice Negative(<1CFU/ml) Negative(4.5MPN/ml)

environmental sample total plate count total coliform count

Swab of chopping board Negative(<10CFU/g) Negative(not detected)

CFU:colonyformingunits; MPN:Mostprobablenumber


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table 3: Retrospective cohort study of 128 attendees of the food poisoning incident

exposuresick Well

RR P value CIexposed not exposed exposed not exposed

Turkey* 44 23 18 43 2.036 <0.01 1.412–2.937

Green salad 19 48 23 38 0.811 0.291 0.533 – 1.188

Honey baked ham 40 27 35 26 1.047 0.790 0.746–1.469

Garlic rice 49 18 37 24 1.329 0.133 0.896–1.973

Sphaghetti 50 17 43 18 1.107 0.600 0.750–1.634

Grilledfish 60 7 52 9 1.224 0.462 0.684 – 2.191

Sauteed prawns 27 40 19 42 1.203 0.281 0.866–1.671

Shepherd’s pie 44 23 36 25 1.329 0.437 0.648–2.722

Chipolata sausage 47 20 35 26 1.318 0.133 0.903–1.079

Vegetable medley 32 35 31 30 0.943 0.730 0.677–1.314

Log cake 26 41 26 35 0.927 0.661 0.658 – 1.305

Fruit cocktail 29 38 35 26 0.763 0.111 0.545 – 1.069

Pizza 10 57 7 54 1.146 0.566 0.740–1.773

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