Hepatitis A molecular epidemiology in the United States, 1996-1997: Sources of infection and implications of vaccination policy

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 greater than or equal to1 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%];). UNSPs P < .001 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.