[An outbreak caused by hepatitis A virus in an institution for the mentally handicapped--detection of hepatitis A virus RNA using CTAB method].

The prevalence of hepatitis A virus (HAV) antibody in people has decreased from year to year in Japan. A sequential outbreak occurred in an institution for the mentally handicapped people in Chiba City in the summer of 1995. Eight people were infected including 7 residents and one staff member. We tested to detect antigen in fecal samples by ELISA and PCR for early diagnosis for hepatitis A infection. Four sera and 5 feces were obtained from 5 patients between 2 and 8 days after the onset of symptoms. The anti-HAV IgM was found to be positive in 4 sera examined. The HAV antigen was detected in 3 out of 5 feces using ELISA. An existence of inhibitor in 2 negative specimens against the ELISA was suggested by the recovery test of added antigen. HAV RNA was extracted by CTAB method from feces and detected in 4 our of 5 specimens in PCR amplification and in all of 5 specimens in nested PCR amplification. The sequence of PCR products in the P1/P2 junction of the HAV genome revealed that the virus associated with the outbreak belongs to HAV subgenotype IA. HAV RNA was detected in ELISA negative specimens and in the specimen from a patient 2 days after the onset of symptoms using PCR amplification by CTAB method. These results indicate that PCR amplification was useful for the early diagnosis of hepatitis A infection.