Hepatitis A

Hepatitis A is an inflammation of the liver caused by the hepatitis A virus (HAV), classified taxonomically within the order Picornavirales, family Picornaviridae, and genus Hepatovirus. It represents one of five recognized hepatitis viruses (A, B, C, D, and E) and is characterized by a single serotype despite the existence of multiple genotypes. The virus possesses a protein shell encapsulating its RNA genome and demonstrates remarkable environmental stability, persisting in the environment and withstanding food production processes routinely used to inactivate bacterial pathogens. Infection confers lifelong immunity following recovery.

The clinical presentation of hepatitis A ranges from asymptomatic infection, particularly common in children under six years of age who may not experience noticeable symptoms, to symptomatic acute hepatitis with varying severity. The incubation period typically spans 14 to 28 days, with symptoms lasting up to eight weeks when they occur and including fever, malaise, loss of appetite, nausea, vomiting, diarrhea, abdominal discomfort, dark-colored urine, and jaundice. Adults experience symptomatic illness more frequently than children, and approximately 10 to 15 percent of infected individuals may experience a recurrence of symptoms during the six months following initial recovery. While most cases resolve without complications, fulminant hepatitis (acute liver failure) occurs rarely but carries high mortality, with risk increasing in older age groups. Extrahepatic manifestations may include joint pains, red cell aplasia, pancreatitis, and lymphadenopathy, though kidney failure and pericarditis are uncommon.

Hepatitis A occurs sporadically and in epidemics worldwide, exhibiting a tendency for cyclic recurrences that reflect changing population immunity levels. Geographic distribution varies considerably based on sanitary conditions, with high endemicity in low- and middle-income countries where poor sanitation and hygiene practices facilitate transmission, intermediate levels in regions undergoing economic transition, and low endemicity in high-income countries with established water and sanitation infrastructure. In high-endemicity areas, approximately 90 percent of children become infected before age ten, most often without symptoms. The 1988 epidemic in Shanghai exemplifies the explosive potential of waterborne outbreaks, affecting approximately 300,000 individuals. WHO estimated 7,134 deaths attributable to hepatitis A in 2016, representing 0.5 percent of mortality from viral hepatitis globally.

The hepatitis A virus is transmitted primarily through the fecal-oral route, occurring when an uninfected and unvaccinated person ingests food or water contaminated with feces from an infected individual. Contaminated food, particularly undercooked or raw shellfish, and water represent common vehicles, with waterborne outbreaks typically associated with sewage contamination or inadequate water treatment. Person-to-person transmission occurs within households through contaminated hands when an infected person prepares food, and close physical contact such as oral-anal sex can also spread the virus. Casual contact among the general population does not efficiently transmit hepatitis A. The virus can persist in the environment for extended periods, contributing to ongoing transmission risks in affected communities.

Anyone who has not been vaccinated or previously infected with hepatitis A virus can acquire infection, though risk varies substantially by geographic setting and exposure context. In high-endemicity areas, most infections occur during early childhood through routine environmental exposure to contaminated water and food. Adults in high-income countries with low endemicity face elevated risk when traveling to endemic regions, and specific behavioral risk factors include injection drug use and oral-anal sexual contact. Immunocompromised individuals and those with pre-existing chronic liver disease may experience more severe outcomes if infected. The elderly population demonstrates higher mortality risk from fulminant hepatitis, warranting particular attention in outbreak settings with significant geriatric populations.

Prevention of hepatitis A centers on vaccination as the primary public health intervention, with the hepatitis A vaccine demonstrating high effectiveness for prevention and providing long-lasting immunity. WHO recommends routine vaccination for children in regions with high endemicity and for high-risk groups who have not been previously vaccinated, including travelers to endemic areas, men who have sex with men, persons who inject drugs, and those with chronic liver disease. Beyond immunization, prevention requires addressing the underlying determinants of transmission through provision of safe drinking water, adequate sanitation infrastructure, improved personal hygiene practices, and food safety measures. The environmental stability of the virus necessitates comprehensive approaches that combine vaccination with infrastructure improvements to achieve sustained disease reduction.

Hepatitis A surveillance should account for the disease's variable clinical expression, as many infections, particularly in young children, remain asymptomatic and may not come to medical attention, potentially underestimating true community transmission intensity. Laboratory confirmation through detection of HAV-specific immunoglobulin M (IgM) antibodies in blood is required for definitive diagnosis, as clinical presentation cannot reliably distinguish hepatitis A from other acute viral hepatitis etiologies. Reverse transcriptase polymerase chain reaction (RT-PCR) testing can detect viral RNA early in infection, even before antibody development, offering utility for early case identification and outbreak investigation. Surveillance systems should monitor both sporadic cases and outbreak patterns, recognizing that epidemics can emerge explosively from contaminated food or water sources and may exhibit prolonged transmission through person-to-person spread within communities.

1. 1 WHO Fact Sheet. Hepatitis A.
2. 2 Wikidata. hepatitis A.
3. 3 Wikipedia. Hepatitis A - Wikipedia.

ICD-10

B15

ICD-11

1E50.0

Total cases

346K

Total deaths

140

Peak month

2010-08

Coverage

4 reporting countries · 2000-01-01 → 2023-12-30