APRIL - JUNE 2015 VOL. 41 NO. 2 57 carriers in a highly endemic community by testing
stool samples obtained from more than 1,000 bucket latrines turned out to be a futile effort. One unexpected consequence of the re-location programme for street hawkers was a large outbreak of 119 cases in a food centre at Taman Jurong in 1975.8 In that outbreak, six acute cases and two carriers selling a variety of cooked food and iced drinks were identified.
Epidemiology
The rapid socio-economic development and urbanisation with corresponding improvements in environmental hygiene and sanitation was the main contributing factor to the rapid reduction of typhoid incidence over the last few decades from 22.8 per 100,000 in 1975 to 5.9 in 1980, 1.2 in 1989 and 0.14 per 100,000 in 2009.9 In 1980, 99.5% of the popula-tion had access to safe water supply and 82% served
with modern sanitation. In 1987, the last bucket latrine was phased out and by 1997, 100% of the population were served with modern sanitation. The declining incidence of typhoid was significantly correlated with infant mortality rate (Spearman’s rank-order coefficient 0.59; p=0.003) (Fig. 7).
The epidemiology of typhoid is currently very similar to that in the industralised nations with more than 90% of the reported cases imported, mainly from the endemic countries in Southeast Asia and the Indian subcontinent.9 Imported cases from India and Indonesia accounted for 48.8% and 20.5%, respectively, of the total imported cases reported during the period 2010-2013.
With the natural attrition of typhoid carriers over the past decades, there is minimum risk of transmission to susceptible contacts through contaminated food within households and in the community. No death from ty-phoid has been reported for more than a decade.
0 1 2 3 4 5 6 7
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Infant mortality rate per 1,000 resident live-births
Incidence per 100,000 population
Year
Infant Mortality Rate (per 1,000 resident live-births) Incidence (per 100,000 population) of typhoid
Figure 7
Typhoid incidence and infant mortality rate in Singapore, 1990 - 2013
(Based on a paper prepared by Ty A, Ang LW and Goh KT for the 9th International Conference on Typhoid and Invasive NTS Disease, organised by Coalition against Typhoid, a programme of Sabin Vaccine Institute, 30 April-3 May 2015)
References
1. Ng SY, Leong KW. Typhoid fever in Singapore. Proceedings of the Alumni Association Malaysia 1955;8:183-9.
2. Koh TS, Goh KT. Enteric fever surveillance in Singapore. Singapore Med J 1976;17:32-7.
3. Kanagaratnam K. Typhoid in Singapore with special reference to Chung Cheng School epidemic, 1965. Sing Pub Hlth Bull 1967; 1:8-20.
4. Goh KT. Surveillance of enteric fevers in Singapore. In: Epidemiological surveillance of communicable diseases in Singapore. Tokyo:
Southeast Asian Medical Information Center, 1983.
5. Cvjetanovic B. Control of enteric fever Singapore Med J 1976; 17:38-9.
6. Koh TS. Food hygiene campaign. Singapore Pub Hlth Bull 1975:15:13-6.
7. Soh CS, Chuo-Ng PH. The ‘Better Food for Better Health’ campaign1975. Singapore Pub Hlth Bull 1975; 16:3-10.
8. Goh KT, Narayanan N. An epidemiological investigation of the 1975 Jurong typhoid outbreak. Singapore Pub Hlth Bull 1976; 7: 40-9.
Comments
However, the problem is far from over, as Singa-pore is situated in a region highly endemic for typhoid.10. Singapore is a well-connected global city with more than 15 million international visitors in 2014, including more than 6 million from the ASEAN region. About 5.6 million residents travelled by air and another 1.7 million by sea. Local residents and foreign workers constituted 35.6 % and 48.1%, respectively, of the imported cases reported during the period 2010-2013. Only about 20%
of Singapore travellers sought pre-travel advice as it was perceived that there was a low risk of acquiring infec-tious diseases while overseas.11 Fortunately, among locally acquired cases, drug-resistant Salmonella Typhi strains remained uncommon with 100% sensitive to ciprofloxacin and ceftriaxone and 73% -100% sensi-tive to ampicillin and co-trimoxazole.9 However, S Typhi resistant to fluoroquinolones among imported cases is a great problem with 70% non-susceptible to ciprofloxacin. Importation of contaminated food is of concern as several outbreaks of enteric diseases had
been reported in the past; viz outbreak of paratyphoid A and oysters from the Philippines in 197912, hepatitis A and cockles from Malaysia in the 1980s and 1990s13,14, norovirus gastroenteritis and oysters from China in 2003/200415, paratyphoid A and coconut from Malaysia in 199616, salmonellosis caused by multi-drug resistant S Typhimurium and dried anchovy from Southeast Asia in 200017.
Various measures have been taken by the licens-ing authority to further strengthen surveillance and control of imported food, including microbiological testing. A high standard of personal, food and envi-ronmental hygiene should continue to be promoted among public food handlers. With ageing population, the intermediate to long-term healthcare institutions are at an increased risk to outbreaks of enteric dis-eases, such as norovirus gastroenteritis, cholera and typhoid, if there are lapses in standards of hygiene and sanitation.18-20 Active surveillance, reporting and epidemiological investigations and control are essen-tial in rapid interruption of transmission of infection.
APRIL - JUNE 2015 VOL. 41 NO. 2 59
Any comments or questions should be addressed to:
The Editor Epidemiological News Bulletin
Communicable Diseases Division, Ministry of Health
The Epidemiological News Bulletin is published quarterly by the Ministry of Health, Singapore
EDITORIAL BOARD Senior Editor Prof Goh Kee Tai Editor
A/Prof Jeffery Cutter Members
A/Prof Stefan Ma Dr Ooi Peng Lim Dr Joanne Tay
SCIENTIFIC ADVISORY COMMITTEE A/Prof Vincent Chow,
Department of Microbiology, National University of Singapore Prof Richard James Coker,
Saw Swee Hock School of Public Health, National University of Singapore Prof Leo Yee Sin,
Director, Institute of Infectious Diseases and Epidemiology and Clini-cal Director, Communicable Disease Centre, Tan Tock Seng Hospital A/Prof Ng Lee Ching,
Director, Environmental Health Institute, National Environment Agency Dr Leong Hon Keong,
Director, Risk Assessment and Epidemiology Department, Agri-Food and Veterinary Authority of Singapore
A/Prof Raymond Lin,
Head, National Public Health Laboratory, Ministry of Health EDITORIAL STAFF
Ms Ang Li Wei Mr Chng Meng Hong Mr Han Hwi Kwang Ms Toh Hai Yin Mr Yuske Kita
9. Ty AU, Ang GY, Ang LW,et al. Changing epidemiology of enteric fevers in Singapore. Ann Aca Med Singapore 2010;39:889-96.
10. Crump JA, Luby CP, Mintz ED. The global burden of typhoid fever. Bull World Health Organ 2004;82:346-53.
11. Lee VJ, Wilder-Smith A. Travel characteristics and health practices among travellers at the Traveller’s Health and Vaccination Clinic in Singapore. Ann Aca Med Singapore 2006;35:667-73.
12. Goh KT. An outbreak of paratyphoid A in Singapore: clinical and epidemiological studies. Southeast Asian J Trop Med Public Health 1981;12:55-33.
13. Goh KT, Chan L, Ding JL., Oon CJ. An epidemic of cockles-associated hepatitis A in Singapore. Bull World Health Organ 1984;62:893-7.
14. Lee HC, Ang LW, Chiew PKT et al. Changing epidemiological patterns of hepatitis A in Singapore. Ann Aca Med Singapore 2011;40:439-47.
15. Ng TL, Chan PP, Phua TH et al. Oyster-associated outbreaks of norovirus gastroenteritis in Singapore. J Infect 2005;51:413-8.
16. Teoh YL, Goh KT, Neo KS et al. A nationwide outbreak of coconut -associated paratyphoid fever in Singapore. Ann Aca Med Singapore1977;26:544-8.
17. Ling ML, Goh KT, Wang GCY et al. An outbreak of multi-drug resistant Salmonella enterica subsp. enterica serotype Typhimurium, DT 104L linked to dried anchovy in Singapore. Epidemiol Infect 2002;128:1-5.
18. Goh KT, Teo SH. Tay L et al. Epidemiology and control of an outbreak of typhoid in a psychiatric institution. Epidemiol Infect 1992;108:221-9.
19.Goh KT, Lam S, Ling MK. Epidemiological characteristics of an institutional outbreak of cholera in Singapore. Trans Roy Soc Trop Med Hyg 1987;81:230-2.
20. Goh KT, Teo SH, Lam S et al. Person-to-person transmission of cholera in a psychiatric hospital. J Infect 1990;20:193-200.
