An Epidemic of Hepatitis A Attributable to the Ingestion of Raw Clams in Shanghai, China

Authors:
  • LKLai-Yi Kang
    Lai-Yi Kang
  • TZTing-Kui Zhou
    Ting-Kui Zhou
  • MHMeng-Dong Hu
    Meng-Dong Hu
  • QPQi-Chao Pan
    Qi-Chao Pan
  • TFTing-Yuan Fu
    Ting-Yuan Fu
  • YHYu-Sheng Huang
    Yu-Sheng Huang
  • SHShan-Lian Hu
    Shan-Lian Hu
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Abstract
An epidemic of hepatitis A in 1988 in Shanghai had an overall attack rate of 40831100,000 population (292,301 cases). The epidemic curve showed three peaks in January and February. A case-control study of 1208 matched pairs supported that clams were the vehicle for the virus (summary odds ratio, 9.47; P < .001). Analysis of subsets who had eaten clams indicated that only 3.5% with hepatitis A had cooked their clams compared with 18.1% without hepatitis A, and those with the disease consumed more clams. A historical cohort study indicated that ∼ 31.7% of the population had eaten clams one or more times between 9 December 1987 and 3 January 1988. The estimated attack rates in those who had and had not eaten clams were 11.93% and 0.52%, respectively (relative risk, 22.94; attributable risk, 11.41%). The three peaks in the consumption curve correlated with those in the epidemic curve, Hepatitis A virus was demonstrated in clams taken from the Shanghai markets and from the catching area.