Changing prevalence of anti-hepatitis A virus in adolescents in a rural township in Taiwan.

Hepatitis A virus (HAV) is transmitted through the oral-anal route. Areas of low prevalence of anti-HAV might have risks for a hepatitis A outbreak even under accidental infection as the source can spread easily. The prevalence of anti-HAV among children in Taipei is reported to be nearly 0%; however, the prevalence in rural areas remains undetermined. Our study aims to realize the prevalence change in a rural area. The prevalence of anti-HAV has decreased to a very low level in recent years and is almost 0% in the generation born after 1984 in rural areas. Therefore, the possibility of an HAV outbreak should be noted. Furthermore, it is also necessary to offer correct information and suggestions concerning hepatitis A for tourists traveling abroad and reentering Taiwan. The prevalence of anti-HAV was 0.96% (2/209) among subjects born between 1984-1985, and 0.6% (1/168) in those born between 1993-1994. The HAV vaccine was not available for at the time of the earlier study, and it is suggested that this figure was caused by natural infection. The only anti- HAV-positive student in the later study had a history of HAV vaccination. We took blood samples for anti-HAV detection from the entire junior high school population in Taihsi Township of Yunlin County in Taiwan. Two cross-sectional studies were conducted in 1999 and 2006, with students born in the years 1984-1985 and 1993-1994 respectively.