Hepatitis A is an acute liver infection caused by Hepatitis A virus, or HAV. It is primarily transmitted through the faecal-oral route, meaning that infection occurs when a susceptible person ingests food or water contaminated with infected faecal material, although close personal and sexual contact can also transmit the virus. Hepatitis A differs fundamentally from Hepatitis B and Hepatitis C because it does not normally establish chronic infection. Most infected people recover completely and develop long-lasting immunity, although illness can occasionally be severe and fulminant hepatitis with acute liver failure can occur. WHO reports that Hepatitis A remains closely associated with sanitation, hygiene and safe-water conditions.
The epidemiology of Hepatitis A varies with sanitation and socioeconomic conditions. In areas where HAV circulation is common, many people acquire infection during childhood, often without recognisable symptoms. In settings with lower childhood exposure, susceptible adolescents and adults may experience symptomatic disease when exposed later in life. Transmission can occur within households, through contaminated food and water, during outbreaks and through particular forms of close sexual contact. The virus is environmentally resilient enough to persist under conditions relevant to food and water contamination. Risk therefore reflects both community-level sanitation and individual exposure. Vaccination and previous infection provide protection, making immunity status an important determinant of susceptibility.
The incubation period of Hepatitis A is usually about 14 to 28 days. Symptoms can include fever, malaise, loss of appetite, nausea, diarrhoea, abdominal discomfort, dark urine and jaundice. Adults are more likely than young children to develop noticeable illness, while many infected young children have no obvious symptoms. Disease severity generally increases with age and underlying liver vulnerability. Some people experience a prolonged or relapsing course after the initial illness, but the infection remains categorically different from chronic viral hepatitis. The absence of symptoms in an exposed person does not exclude infection, which is relevant during outbreaks because individuals may transmit HAV without recognising that they are infected.
Diagnosis of Hepatitis A cannot reliably be made from symptoms alone because acute HAV infection resembles other causes of acute hepatitis. Detection of HAV-specific immunoglobulin M antibodies in blood is a principal diagnostic method for recent infection. Molecular testing for HAV RNA can also be used in specialised circumstances and may identify infection early. Liver biochemical tests commonly show evidence of acute hepatocellular injury but do not identify HAV specifically. Clinical assessment may also consider exposure history, vaccination status, outbreak circumstances and alternative causes of hepatitis. Correct diagnosis matters because the infection-control implications differ from those of bloodborne chronic viruses such as Hepatitis B and Hepatitis C.
There is no specific routine antiviral treatment for Hepatitis A. Management is generally supportive, focusing on adequate fluids, nutrition and symptom control while the immune system clears the infection. Severe disease or acute liver failure may require hospital treatment and specialist care. Because the liver can be vulnerable during acute hepatitis, unnecessary medications or substances that can adversely affect hepatic function should be avoided under appropriate medical guidance. Most people recover fully, although fatigue and other symptoms can persist for weeks or months. Chronic antiviral suppression is not required because HAV normally does not persist as a chronic infection.
Prevention of Hepatitis A combines vaccination with sanitation, hygiene and food-safety measures. Safe drinking water, appropriate sewage disposal and thorough hand hygiene reduce environmental transmission. Vaccination provides effective individual protection and is particularly relevant for populations or settings in which exposure risk is increased. Post-exposure vaccination or immune-based measures may be considered in specific circumstances according to public-health guidance. The vaccine does not treat an established infection. Prevention strategies are therefore directed at interrupting transmission and establishing immunity before exposure. WHO recommends considering Hepatitis A vaccination within comprehensive prevention programmes according to local epidemiology and public-health circumstances.
Hepatitis A should not be confused with the general term Hepatitis. Hepatitis describes liver inflammation from many causes, whereas Hepatitis A specifically identifies infection with HAV. It should also be distinguished from Hepatitis B and Hepatitis C because the principal transmission routes, chronicity and treatment approaches differ. HAV is predominantly faecal-oral, while HBV and HCV are principally associated with infected blood or other body-fluid exposure. HAV generally resolves without chronic liver disease, whereas chronic HBV and HCV can lead to cirrhosis and liver cancer. These distinctions are fundamental to interpreting laboratory results, assessing contacts and selecting preventive measures.
Historically, Hepatitis A has been strongly linked to sanitation and water quality because its transmission depends heavily on faecal contamination. Large outbreaks can occur when contaminated food or water reaches susceptible populations, while person-to-person transmission can sustain prolonged community outbreaks. The global public-health burden remains significant despite the availability of effective vaccination and sanitation measures. The infection is therefore an example of how environmental infrastructure, behavioural practices, immunisation and clinical medicine intersect. Its most important biological distinction is that HAV produces an acute infection that the immune system normally clears, leaving immunity, rather than the persistent viral replication characteristic of chronic Hepatitis B or Hepatitis C.
