A foodborne disease outbreak is defined as the occurrence of
two or more cases of a similar illness resulting from the ingestion of
a common food, or if the food vehicle was undecided, sharing a
common meal or food facility. The etiology was classified as
confirmed if V. parahaemolyticus was isolated from the implicated
food, equipment or utensils used, and faecal samples or vomitus
from patients (Ministry of Health of the People's Republic of China,
1996). Outbreaks that did not meet these criteria were not reported
to NFDSN by participant provinces. Outbreaks with multiple etiology
were excluded from the analysis.