Viral hepatitis: prevention and prophylaxis.

Hepatitis A is spread by fecal-oral transmission and accounts for 25% of the cases of sporadic hepatitis in this country; fatal cases have been documented but are unusual, and chronic hepatitis A has not been documented. Hepatitis B is spread by varied routes of transmission, fecal-oral being the least important, and accounts for half the cases of sporadic hepatitis in this country; fatal cases are well documented and chronic hepatitis B is common. The only documented route of transmission of non-A, non-B hepatitis is parenteral; fatal and chronic cases have been documented, and a quarter of the cases of sporadic hepatitis are non-A, non-B. Diagnosis of the etiology of viral hepatitis cannot be determined on clinical grounds but must be made through serologic tests.