For professionals:

• Hepatitis A virus is a RNA virus, 27nm enterovirus
• HAV virus is shed in stool during the period from 7 ~ 10 days prior to one week after the onset of the illness, therefore it is not easy to prevent the infection from HAV.

• Keeping food and dining utensils clean and uncontaminated for prevention of Infection from HAV.
• Clinical symptoms usually subside 2 ~ 6 weeks after the onset of symptoms and natural cure occurs in 4~8 weeks.

• 1~2 % of the cases will come out to be fulminant hepatitis and die within 2 weeks.

• HAV superinfection on patient with chronic hepatitis C or B may develop into fulminant hepatitis. (NEJM, 1998; 338:286).

• In recent studies, the age incidence of HAV has shown a tendency of more cases and more severe clinical course and outcome among older persons and cases with extrahepatic complications of acute renal failure, pure red cell anemia, hypoplastic anemia, hemolytic anemia and idiopathic thrombocytopenic purpura.

• Severe clinical conditions may be caused by variant strains through cytopathic effect (Beneduce F, et al. 1995; Virus Res 36: 299-309).

• Recently, homosexuality of men and HIV victims are included in high risk group of HAV infection. (Ishida T. et al.; Jpn.J.Infect.Dis. 1999; 52: 131-132. MMWR; 1998; Vol 47, No 34;708)

• Successful control of HAV infection in Taiwan
  • Infection rate in western plain region of Taiwan:
  • 1981: above the age of 15 yrs ----- 95% of the people have
  been infected.
  • 1989: 15 yrs old -----33%, 13 yrs old ----- 15% of the population
  have been infected.
  • It means that there has been a remarkable improvement in environmental sanitation in western Taiwan since after 1981.
  • On the contrary, the infection rate in eastern mountain region of Taiwan:
  • 1991: above 15 yrs old -----95 ~ 100%
  • 7 ~ 14 yrs old ----- 85 ~ 90%
  • 1 ~ 6 yrs old ----- 75%
  • Thus, we can evaluate the status of the environmental sanitation of a region by the infection rate of viral hepatitis A .
  • Most of the population in western plain region, who were born before 1966, have already been infected with HAV and having antibody to HAV, therefore, they will not be reinfected from HAV.

  • However, those born after 1980, having grown under the well controlled environmental sanitation and never infected by HAV, are susceptible to infection by HAV because they have no antibody to HAV.

  • Those born between 1967 to 1979 are having antibody to HAV in different proportion, the lower in those born later.

  • Therefore, most of the population group born after 1980 in the western region of Taiwan are susceptible to hepatitis A virus infection and should receive vaccination against hepatitis A virus before traveling to high endemic regions as those countries of South-Eastern Asia and mainland China, including the eastern mountain region of Taiwan.

• In Japan, only below 1% of the population born after 1954 have been infected from HAV in the survey by Kiyohara in 1994, therefore they are all susceptible to HAV infection. The situation is the same in all developed countrues.
• In war time or the natural disaster causing poor environmental sanitation, there will be a high possibility of epidemics of viral hepatitis A.
  
• For reference:
  
  • CDC - Factsheet about HAV
  • CDC - Recomendation for prevention
  • CDC - FAQ about information on hepatitis A
• For more information refer to:
  
  • Clinical features of acute viral hepatitis:
  • Clinical features of chronic hepatitis:
  • Acute liver failure:
  • Treatment for viral hepatitis:
  • Prognosis of chronic hepatitis:
  • Prevention of viral hepatitis:
  • Prevention of viral hepatitis for international travelers: (For consumers)
  • For interpretation of liver test, refer to homepage
• References: