Hepatitis A

甲型肝炎

Evidence-backed information EN 5/7 applicable sections · ZH 5/7 applicable sections Updated Oct 23, 2026

Hepatitis A is a liver inflammation caused by the hepatitis A virus and is transmitted through ingestion of faecal-contaminated food or water, inadequate sanitation, poor hygiene, or oral-anal contact ^[1]. Globally it caused an estimated 35,569 deaths in 2023, representing 2.6% of viral hepatitis mortality ^[1]. The infection occurs sporadically and in epidemics, with recurrence cycles and explosive food- or waterborne outbreaks ^[1].

Read the full clinical and epidemiological profile 6

Definition

Hepatitis A is an inflammation of the liver resulting from infection with the hepatitis A virus ^[1]. It is a form of viral hepatitis that, unlike types B and C, does not lead to chronic liver disease ^[1].

Clinical features

The illness ranges from mild to severe and can rarely progress to fulminant hepatitis with acute liver failure that is often fatal ^[1]. Infected young children frequently show no noticeable symptoms ^[1].

Epidemiology

Hepatitis A appears both sporadically and in epidemics worldwide with cyclic recurrences, and contaminated-food or water outbreaks can be explosive, as seen in a 1988 Shanghai event affecting around 300,000 people ^[1]. The virus persists in the environment and resists standard food-control processes for bacteria ^[1]. Geographical areas are classified as high, intermediate, or low infection levels; low- and middle-income countries with poor sanitation see 90% of children infected by age 10, usually without symptoms, whereas high-income countries show low rates ^[1].

Transmission

The virus spreads mainly when an uninfected and unvaccinated person ingests food or water contaminated with faeces from an infected individual ^[1]. It is linked to unsafe water or food, inadequate sanitation, poor personal hygiene, and oral-anal sex ^[1]. Person-to-person transmission can sustain prolonged community outbreaks over months ^[1].

Prevention

Vaccination is a core preventive measure, with catch-up hepatitis A immunization recommended during adolescent visits to complete early childhood schedules ^[2]. Combined hepatitis A and B vaccine may be considered for specific populations such as rheumatoid arthritis patients without hepatitis B antibodies ^[3]. General prevention also depends on safe water, adequate sanitation, and good hygiene to limit faecal-oral exposure ^[1].

References

1 World Health Organization. Hepatitis A [Internet]. cited 23 Oct 2026. Available from: https://www.who.int/news-room/fact-sheets/detail/hepatitis-a
2 Bernstein HH et al. The Need to Optimize Adolescent Immunization. Pediatrics. 2017 Mar. PMID: 28167517. doi: 10.1542/peds.2016-4186. PubMed: https://pubmed.ncbi.nlm.nih.gov/28167517/
3 Brenol CV et al. 2012 Brazilian Society of Rheumatology Consensus on vaccination of patients with rheumatoid arthritis. Rev Bras Reumatol. 2013 Feb. PMID: 23588512. PubMed: https://pubmed.ncbi.nlm.nih.gov/23588512/