Ascertainment of secondary cases of hepatitis A--Kansas, 1996-1997.

Each year, 25,000-30,000 cases of hepatitis A are reported in the United States. The most common infection source (22%-26%) is household or sexual contact with a person already infected with hepatitis A virus (HAV) (i.e., the source-patient). In Kansas during 1992-1997, contact with a source-patient was reported by 39% of persons with hepatitis A. Cases reported in 1996 and 1997 were studied retrospectively to determine the reasons for the apparently high proportion of secondary cases and to evaluate missed opportunities for prevention (i.e., postexposure prophylaxis with immune globulin [IG]). Results of this investigation indicate that persons with hepatitis A often were classified incorrectly as secondary cases and that some correctly identified secondary cases represented missed opportunities for prevention.