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

Abstract

An epidemic of hepatitis A in 1988 in Shanghai had an overall attack rate of 4083/100,000 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 less than .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 approximately 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.

High-Pressure Inactivation of Hepatitis A Virus within Oysters

“…In fact, HAV and other viruses are readily identified in shellfish harvested in certain European regions (3,10,17,29,31). HAV-contaminated shellfish have caused significant outbreaks of human disease (5,11,22). Furthermore, global trade of virally contaminated shellfish has resulted in outbreaks and dissemination of HAV and other exotic virus strains to geographic areas where they are not endemic (5,19,27,35,36).…”

Scientific Opinion on the minimum hygiene criteria to be applied to clean seawater and on the public health risks and hygiene criteria for bottled seawater intended for domestic use

“…Foods of primary importance are those susceptible to be contaminated at the pre-harvest stage such as bivalve molluscs, particularly oysters, clams and mussels, salad crops, such as lettuce, green onions and other green leafy vegetables, and soft fruit, such as raspberries and strawberries. All these types of food have been implicated in foodborne HAV outbreaks (CDC, 1997;Halliday et al, 1991;Pinto et al, 2009;Shieh et al, 2007;Wheeler et al, 2005). Epidemiological data therefore indicate that infectivity is retained within shellfish.…”

“…The virus can also retain infectivity following freezing or in ice (Butot et al, 2008;Carter, 2005 The first documented shellfish-borne outbreak of -infectious hepatitis‖ occurred in Sweden in 1955, when 629 cases were associated with raw oyster consumption (Roos, 1956). However, the most significant outbreak of HAV infection occurred in Shanghai, China, in 1988, in which almost 300,000 cases were caused by consumption of clams harvested from a sewage-polluted area (Halliday et al, 1991). This is the largest virus-associated outbreak of food poisoning ever reported.…”

Exposure to enteroviruses and hepatitis A virus among divers in environmental waters in France, first biological and serological survey of a controlled cohort

“…Enteroviruses, hepatitis A virus (HAV) and rotaviruses can cause waterborne epidemics [9][10][11][12][13], but there is little quantitative information on the relation between water quality and disease attack rates after bathing and diving in contaminated water [14][15][16]. The detection of enteric viruses in large volumes of water presents major difficulties in collecting a representative sample and in concentrating the viruses for laboratory investigations.…”