The risk of acquiring hepatitis from sewage-contaminated water.

There is little information on the risk of acquiring hepatitis A from drinking sewage-contaminated water. In a large outbreak of gastrointestinal illness at Crater Lake National Park, Oregon, a US national park, in June-July, 1975, approximately 100,000 persons were exposed to sewage-contaminated water. State health departments reported three cases of Crater Lake-associated hepatitis A for a rate of 12/100,000 per year, comparable to the reported US incidence of non-B hepatitis 10/100,000 per year. Questionnaire survey of 3997 overnight park visitors revealed five cases of hepatitis A, occurring in 2206 persons who drank water but did not receive immune serum globulin (ISG) within two weeks of exposure, an attack rate of 0.23%. The association between drinking park water and subsequently developing hepatitis was not statistically significant. No cases of hepatitis occurred in 320 park staff and family members, repeatedly exposed to contaminated water. The authors do not recommend routine use of prophylactic ISG for similar outbreaks of gastroenteritis caused by sewage-contaminated water but suggest close surveillance of the exposed group, and careful consideration of risk factors and costs.