Pathology of illness: The incubation period for hepatitis A virus is generally 2–6 weeks, and with a sudden onset of symptoms including fever, headache, malaise, fatigue, anorexia and nausea, usually followed by vomiting and abdominal pain. When symptoms do occur, they are usually mild and recovery is complete in 1–2 weeks. Many infections do no result in clinical illness especially in children (Grohmann 1997). Less than 0.4 per cent of reported cases in the United States are fatal, usually occurring in the elderly (Sobsey et al. 1991; FDA 2003). Recovery is complete and gives lifelong immunity to further infection. Immunocomprised individuals are more susceptible to infection (Sobsey et al. 1991; FDA 2003).
The mechanisms by which illness is caused are not fully understood, but viral particles are thought to replicate in the gastrointestinal tract and then the liver where they cause cellular damage.
