上海市闵行区甲型肝炎暴发流行的调查分析

闵行区1988年1月15日至2月15日甲型肝炎(甲肝)流行期间共报告2449例病人,罹患率为23.2‰,其中20～29岁、30～39岁两组罹患率分別为41.4‰和39.9‰。调查表明本次流行系生食毛蚶所致。证据如下:(1)两次供应毛蚶均先于两流行峰前1个月,正好是甲肝的潜伏期,且供应量多流行峰亦高;人群生食毛蚶率高达27.9％;(2)病例对照调查提示甲肝病人吃蚶率为94.4％,极显著高于一般人群(27.9％)和对照病人(28.7％),OR值高达72.0(95％CL:25.9～200.3),且吃蚶量越多OR值越高;(3)人群抽样调查发现吃毛蚶者较未吃者发生肝炎的相对危险性为29.37倍,归因于吃毛蚶的病例占发病数的93.1％。

INVESTIGATION OF THE PREVALENCE OF HEPATITIS A OUTBREAK IN MINHANG DISTRICT, SHANGHAI

From January 15th to February 15 th, 1988, 2449 cases of acute hepatitis A were reported in Minhang, Shanghai, a district of 105, 476 residents. The attack rate was 23.2 per thousand population with 41.4% among those of 20-29 years old, 39.9% 30-39 years old, and none elder than that. Investigation disclosed that the cause of outbreak was due to having eaten raw clams, Arca (Anadara) subcrenata,. The facts found to confirm the source of infection were: (1) two supplies of clams preceded the two epidemic peaks by one month, corresponding to the incubation period of hepatitis A; and up to 27.9% people in sample population were found to have taken these raw clams; (2) a case-control study indicated that 94.4 % of hepatitis A patients had history of having eaten clams, significantly higher than the percentages of general population (27.9%) and control patients (28.7%), and that the odds ratio (OB) was up to 72.0 (95% confidence level: 25.9-200.3); the more olams one consumed, the higher the OR value would be; and (3) sampling survey of the population showed that the relative risk (RR) of acquiring hepatitis A infection in those who had taken the clams was 29.37 times higher that in those who had not; 93.1% of the total hepatitis A cases were estimated to be attributed to having eaton contaminated clams.