OBJECTIVETo compare the field epidemiological investigation and the criminal investigation on a nitrite poisoning event caused by deliberate contamination.

METHODSCases were searched according to the definition of the disease. Information on the histories of onset and diet of all the cases and normal population on site, were investigated face to face. Information as ingredients, processing and sales of foods was also gathered. Samples were collected and nitrite detection were performed. Relevant materials were searched, cases were interviewed and data related to criminal results were collected.

RESULTSPoisoned persons were staff of a big company in Longgang district of Shenzhen. The overall attack rate was 56.25% (63/112), with suspected and confirmed rates as 41.96% and 14.28%, respectively. The fatality rate was 3.17% (2/63). Clinical manifestation and effect of treatment were in accordance with the characteristics of an episode related to acute nitrite food poisoning in terms of factors as the time of onset, involving different age, sex and jobs of the patients. A total of 191 samples, including vomits from patients and seven batches of food and environment samples, were collected, with a positive detected rate of nitrite as 18.84%. Information gathered from the field environment, food distribution and processing supported the assumption that this was an incident of nitrite poisoning event with intention.

RESULTSfrom the criminal investigation showed that the suspect stemmed from the market management rivalry, bought nitrite, dissolved and spread on food stalls F9 and F10.

CONCLUSIONThis event of intentional nitrite release resulting in food contamination which further leading to food poisoning, was completely proved by the joint efforts of the teams and expertise from the field epidemiology survey and the criminal investigation.