Hepatitis A Molecular Epidemiology in the United States, 1996–1997: Sources of Infection and Implications of Vaccination Policy

Abstract

BACKGROUND: The genetic relatedness of hepatitis A virus (HAV) isolates was determined to identify possible infection sources for case patients in the Sentinel Counties Study of Acute Viral Hepatitis. METHODS: A 315-nucleotide segment of the VP1-P2 region of the HAV genome was amplified and sequenced from serum of case patients and analyzed together with risk-factor data. RESULTS: Of 508 HAV-RNA-positive case patients, 449 (88.4%) were interviewed, and 255 (50.1%) reported >/=1 risk factor. Some 123 unique nucleotide sequence patterns (UNSPs) were identified--77 (62.6%) from only 1 case patient and the rest in 2-99 persons. Among international travelers, a single person was more often infected with a single type of UNSP (17/54 [31.5%]), compared with other case patients (48/393 [12.2%]; P<.001). UNSPs from travelers to Mexico (33/37 [89.2%]) clustered with those from Hispanic children (47/49 [95.9%]). Of 119 men who had sex with men, 96 (80.7%) had the same or similar UNSPs, which were also found in 37 men and 10 women with no identified infection source. CONCLUSION: HAV is often transmitted within networks of persons with similar risk factors, which may be the infection source for others in the community.