and T.F. generation and high risk population Belotecan hydrochloride may prevent outbreak in Japan. Introduction Hepatitis A virus (HAV) infection occurs sporadically and is primarily transmitted via the fecal-oral route, bearing a high potential for either cyclic recurrence or explosive worldwide spread as an epidemic, especially in the case of a food or waterborne outbreak1. In addition, sexual transmission, especially in men who have sex with men have been documented2. However, HAV endemics are strongly related to socio-economic conditions, and Rabbit Polyclonal to RCL1 such infections can be reduced by improving the hygiene, sanitary habits, and water supply of the population and by using HAV vaccination. It has been estimated that millions people worldwide are infected with HAV each year. In 2015, there were approximately 11,000 deaths from HAV, contributing to 0.8% of the total death from viral hepatitis3,4. Although vaccination against HAV infection has been available since the early 1990s, it is not widely used5,6 and most people maintain immunity via exposure resulting from a childhood infection. The severity of HAV infection greatly depends on the age at the time of viral entry. Approximately 90% of infections were asymptomatic among infected children under 5 years of Belotecan hydrochloride age, whilst approximately 70% of infections cause the typical symptoms of acute hepatitis among older children and adults, of which less than 1% may progress into fatal fulminant hepatitis7. The severity of disease increases with age; more than 53% of adults 60 years old require hospitalization for acute hepatitis8. HAV is a self-limiting disease that can resolve without inducing chronic infection or other manifestations. Individuals experiencing HAV infection with or without symptoms have lifelong immunity; in contrast, immunization through inactivated or live attenuated HAV vaccines does not guarantee lifelong immunity9. With a high proportion of the population not immune Belotecan hydrochloride to HAV, deterioration in existing sanitation and water supply could lead to a massive transmission of HAV. HAV endemicity levels vary worldwide, and regions are separated into three main categories: high, intermediate, and low endemic areas. These three regions indirectly indicate the socioeconomic level, including the sanitation, hygiene, and water supply of the country. In highly endemic countries, more than 90% of children have been exposed to HAV infection by 10 years of age, while 50% have seroconverted into anti-HAV positive by 15 years of age in intermediate countries and by 30 years of age in low endemic countries10. These three categories (high endemic areas, intermediate endemic areas, and low endemic areas) are determined based on whether the positive rate of anti-HAV IgG in human serum in the study population is 15%, 15C50%, or 50%11. The National Institute of Infectious Disease in Japan conducted nationwide sero-surveys on HAV prevalence among the general population four times, in 1973, 1984, 1994, and 2003. Using these large scale nationwide surveys, the overall anti-HAV prevalence was reported to be 8% (1973), 10% (1984), 19.4% (1994), and 12.2% (2003). All studies revealed very low anti-HAV prevalence among the young population and a gradual increase in anti-HAV positivity after 50 years of age. Moreover, 10 year shift in anti-HAV prevalence in each age group was also found between the studies, showing persistent very low anti-HAV prevalence among the general population, especially in young adults under 50 years of age12C14. After 2003, no more reports on anti-HAV prevalence among general population have been documented in Japan. The very low prevalence previously reported may threaten possible mass transmission of HAV in Japan. Therefore, it is important to know the current situation of HAV infection among the general population in Japan. We conducted this study to investigate the prevalence of anti-HAV.