Epidemiological investigation of a food-borne gastroenteritis outbreak caused by Norwalk-like virus in 30 day-care centres.
In March 1999, an outbreak of gastroenteritis occurred affecting 30 day-care centres served by the same caterer. A retrospective cohort study was performed in 13 randomly selected day-care centres to determine the source and mode of transmission. Electron microscopy and PCR were used to verify the diagnosis. The overall attack rate (AR) was 37% (195/524): 30% in children and 62% in adults. Modified by the age of the patient, eating pumpkin salad served on 1 March was associated with becoming an early case (odds ratio = 3.9; 95% confidence interval 1.8-8.8). No significant association was found between food consumption and becoming a late case. The primary food-borne AR was 27% and the secondary AR was 14%. The same genotype of Norwalk-like virus was found in 5 cases and in 1 ill and 1 asymptomatic food-handler. Contamination by 1 of the food-handlers seems the most likely route of spread of the virus and underlines the importance of strict hygienic routines.
Götz
Hannelore
H
Department of Epidemiology, Swedish Institute for Infectious Disease Control. gotzh@ggd.rotterdam.nl
de Jong
Birgitta
B
Lindbäck
Johan
J
Parment
Per Arne
PA
Hedlund
Kjell Olof
KO
Torvén
Maria
M
Ekdahl
Karl
K
D000328:Adult; D017250:Caliciviridae Infections / Q000453:epidemiology* / Q000821:virology*; D002648:Child; D002656:Child Day Care Centers; D002675:Child, Preschool; D015331:Cohort Studies; D028464:Cucurbita / Q000821:virology; D004196:Disease Outbreaks; D005511:Food Handling / Q000592:standards; D005516:Food Microbiology; D005759:Gastroenteritis / Q000453:epidemiology* / Q000821:virology*; D006801:Humans; D007223:Infant; D016015:Logistic Models; D029322:Norovirus / Q000235:genetics / Q000302:isolation & purification* / Q000648:ultrastructure; D016133:Polymerase Chain Reaction; D012189:Retrospective Studies; D013997:Time Factors