Open Outbreak

Hepatitis A

Also known as: HAV, hepatitis A virus

Hepatitis A is a liver infection caused by hepatitis A virus. It is usually an acute illness, which means it does not become a lifelong infection. The virus spreads mainly by the fecal-oral route: when tiny amounts of stool from an infected person get into another person’s mouth, often through close personal contact, contaminated food or water, dirty hands, or some sexual contact. WHO says infection is typically self-limiting and rarely fatal, but some people have more severe illness that can last for months. Risk is often higher for unvaccinated people in close-contact settings and for certain groups in low-endemicity countries, including travellers to endemic areas, men who have sex with men, people who inject drugs, and people with chronic liver disease. Vaccines exist and WHO says they should be used for prevention, including outbreak control and post-exposure prophylaxis for close contacts. Treatment is mainly supportive care rather than an antiviral cure.

Key facts

TransmissionFecal-oral spread, usually by direct person-to-person contact or contaminated food or water; also through dirty hands, close physical contact, and some sexual contact.
Incubationunknown
Case fatalityunknown; WHO describes hepatitis A as rarely fatal.
Reproduction numberunknown
VaccineYes. Hepatitis A vaccine is available and WHO recommends it for prevention and outbreak control in people at increased risk.
TreatmentNo specific antiviral treatment was identified in the sources used here; care is mainly supportive.
ReservoirHumans
Endemic regionsWorldwide. Higher endemicity is described in developing countries and some settings are classed as high, intermediate, or low endemicity.

Transmission

Hepatitis A spreads mainly by the fecal-oral route. In plain language, that means the virus moves from stool into another person’s mouth. WHO says this usually happens through direct person-to-person contact or through food or water contaminated with feces. It can also spread through dirty hands, close physical contact, and sexual contact. In the 2017 WHO outbreak notice, sexual transmission was highlighted especially among men who have sex with men, with oral-anal contact named as an important risk. A literature source also describes spread as generally person to person, or by oral intake after fecal contamination of skin or mucous membranes, with food- and water-borne spread less common. This pattern means crowding, poor sanitation, and close personal networks can all matter. Because spread depends so much on hygiene and contact, vaccination, handwashing, safer sex measures, and food safety are central tools for prevention.

Symptoms and severity

Hepatitis A affects the liver. WHO says infection is typically acute and self-limiting, meaning most people recover and it does not become chronic liver disease. The encyclopedia overview used for background says many cases have few or no symptoms, especially in younger people. When illness does happen, symptoms can include jaundice, fever, nausea, vomiting, diarrhea, and abdominal pain. WHO notes that some patients develop more severe symptoms that may last for a few months. In the 2017 outbreak notice, WHO also said no deaths had been reported in connection with that event and described hepatitis A as rarely fatal overall. For a worried reader, the key point is that hepatitis A can make adults quite unwell, but the usual course is recovery rather than long-term infection. The sources used here did not provide a single reliable overall case-fatality percentage, so that figure is best treated as unknown on this page.

Treatment and vaccines

The main protection against hepatitis A is vaccination. WHO says countries with low endemicity should routinely offer hepatitis A vaccine to people at increased risk, including travellers to endemic areas, men who have sex with men, people who inject drugs, and people with chronic liver disease. WHO also says vaccine should be preferred for pre-exposure and post-exposure prophylaxis, such as for close contacts of a known case. During shortages, WHO noted that countries may consider a single-dose schedule to help control outbreaks. The literature source from 2020 also describes hepatitis A as vaccine-preventable. For treatment, the sources used here do not identify a specific antiviral cure. Instead, hepatitis A is described as an acute, self-limited disease, so management is mainly supportive care while the illness runs its course. In practice, that means rest, fluids, and medical assessment if symptoms are severe or if the person has other liver disease or signs of liver failure.

Where it occurs

Hepatitis A occurs worldwide, but the pattern is not the same everywhere. A review article says hepatitis A is endemic in developing countries, where many residents are exposed during childhood. In contrast, it says exposure rates have fallen in developed countries as hygiene and sanitation improved. WHO describes countries and populations as having high, intermediate, or low endemicity. In low-endemicity countries, hepatitis A rates are usually low, but outbreaks can still happen in adolescents and adults in higher-risk groups, including men who have sex with men, people who inject drugs, travellers to endemic areas, and some closed communities. WHO also notes that in high-endemicity settings, infections are common but disease may be less conspicuous because many infections occur earlier in life. For readers, this means hepatitis A is not limited to one continent. Risk depends on local sanitation, vaccination coverage, travel, and close-contact networks rather than on geography alone.

Recent history

On this site’s archive, hepatitis A has appeared rarely: there is 1 archived WHO-era event on record since 1996, and 1 site record is listed, “Hepatitis A outbreak, Costa Rica [monitoring].” The WHO Disease Outbreak News item found in this session was published on 2017-06-07 and described multi-country outbreaks mainly affecting men who have sex with men in Europe and the Americas. WHO reported that between 2016-06 and mid-2017, 15 countries in the European Region had reported 1,173 outbreak-related cases linked to three distinct multinational outbreaks. The same WHO notice also described 706 reported hepatitis A cases in Chile as of 2017-05-05 and an increase among men who have sex with men in New York City. WHO’s concern at the time was not only ongoing spread, but also limited global vaccine availability. Taken together, the archive and WHO material suggest hepatitis A is common globally but has generated relatively few high-profile WHO outbreak notices on this site.

What to watch

The main warning signs would be changes that suggest hepatitis A is spreading faster, reaching new groups, or becoming harder to control. WHO’s 2017 notice points to several such signals: unusual increases in cases in low-endemicity countries, spread into new countries or the wider general population, ongoing person-to-person transmission in close-contact or sexual networks, and pressure on vaccine supply. Another practical signal is outbreaks linked to contaminated food or water, because those can expose many people quickly. In places that usually report few cases, clusters among adults may matter more because illness can be more noticeable and severe than in young children. Public health teams would also watch whether close contacts are being vaccinated quickly enough and whether vaccine shortages are limiting outbreak response. The sources used here do not report antiviral resistance or a change toward chronic infection. So the biggest concerns, based on current evidence, are broader geographic spread, sustained transmission in high-risk networks, and insufficient vaccine availability during outbreaks.

Related outbreaks

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