An outbreak of norovirus gastroenteritis on an Israeli military base.
BACKGROUND
Noroviruses (NVs) are a predominant cause of viral gastroenteritis outbreaks, but they are difficult to identify because they cannot be cultivated in cell culture. Therefore, reverse-transcriptase polymerase chain reaction (RT-PCR) assays are widely used in the testing of clinical stool specimens for NV. However, testing of perianal swabs in the context of an outbreak is considered to be an insensitive method for identification of NV using the RT-PCR technique. An outbreak of acute gastroenteritis involving 159 soldiers on a training base of the Israel Defense Force in December 1999 allowed us to evaluate this identification method.


METHODS
An epidemiologic investigation, a sanitation survey and a case-control study of exposure to different food items served up to 48 h preceding the outbreak were conducted. Stool samples in the form of post-defecation perianal swabs were collected from 24 ill personnel and three non-ill food handlers. Swabs were tested for the presence of NV by RT-PCR assay.


RESULTS
Epidemiologic data were consistent with a pointsource food-borne outbreak which was associated with consumption of fresh vegetable salad in the base mess hall (OR = 4.38, 95% CI 1.51-13.35). Both epidemiologic and clinical features were suggestive of gastroenteritis caused by NV, and upon laboratory analysis perianal swabs from four of 24 cases were positive for NV.


CONCLUSIONS
The combination of practical specimen collection with perianal post-defecation swabs, and the utilization of a molecular epidemiology approach, can simplify the rapid identification of outbreaks caused by NVs.
Grotto
I
I
Army Health Branch, Israel Defense Force Military Corps, Military Post 02149, Israel, 19 Izmargad Street, Hod Hasharon 45045, Israel. grotto@netvision.net.il
Huerta
M
M
Balicer
R D
RD
Halperin
T
T
Cohen
D
D
Orr
N
N
Gdalevich
M
M
D000328:Adult; D017250:Caliciviridae Infections / Q000453:epidemiology* / Q000473:pathology; D016022:Case-Control Studies; D004196:Disease Outbreaks; D016021:Epidemiologic Studies; D005506:Food Contamination; D005511:Food Handling; D005759:Gastroenteritis / Q000453:epidemiology* / Q000473:pathology / Q000821:virology*; D006801:Humans; D007557:Israel / Q000453:epidemiology; D008297:Male; D008889:Military Personnel; D029322:Norovirus / Q000472:pathogenicity*; D015995:Prevalence; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012499:Sanitation