An outbreak of Salmonella gastrointestinal illness in a military camp.
BACKGROUND
Non-typhoidal Salmonellae are important causes of bacterial food-borne infection, especially in institutional settings. An outbreak of gastrointestinal infection occurred in a military camp in January 2007, and an epidemiological outbreak investigation was conducted.


METHODS
A survey was conducted on soldiers in the camp on their clinical symptoms, and recent meals consumed. After determining the affected meal, a subsequent survey was conducted on those who had eaten the meal. A case-control study was then performed to determine the outbreak's likely food source. Laboratory tests were also conducted to determine the bacteriological cause.


RESULTS
Of the 94 responders, 55 (58.5%) met our case definition of gastrointestinal illness. The dinner on 9 January was the most likely affected meal, with the onset of symptoms occurring within 6 to 36 hours. The mashed potato was the most likely food source with an attack rate of 80.7% for those who consumed it versus 32.7% for those who did not (P <0.01). From the multivariate analysis, the mashed potato remained the only food item independently and significantly associated with infection, with a relative risk of infection 9.49 times those who did not consume it (95% CI, 2.73-32.97). Salmonella group E was cultured from 4 individuals. Although no specific contamination was identified, the mashed potato was stored for more than 5 hours before the last serving.


CONCLUSIONS
Risk during preparation of large quantities of food should be identified a priori, and measures taken to reduce them, to prevent outbreaks.
Army Medical Services, Singapore Armed Forces, Singapore. vernonljm@hotmail.com
Vernon J
VJ
Lee
Alan E S
AE
Ong
Matthew
M
Auw
D016022:Case-Control Studies; D004196:Disease Outbreaks; D005516:Food Microbiology; D005759:Gastroenteritis / Q000209:etiology*; D008887:Military Medicine; D012475:Salmonella / Q000302:isolation & purification; D012478:Salmonella Food Poisoning / Q000209:etiology*; D012846:Singapore; D011198:Solanum tuberosum