Open Outbreak

Hepatitis E

Also known as: HEV, hepatitis E virus

Hepatitis E is a liver infection caused by hepatitis E virus. It spreads mainly when tiny amounts of infected stool get into drinking water or food. In many places this is linked to poor sanitation, flooding, conflict, and crowded camp settings. Some types of the virus also spread from animals to people, especially through uncooked or undercooked meat. Most infections are short and clear on their own within a few weeks, but some become severe. WHO says the incubation period is 2 to 10 weeks, usually about 5 to 6 weeks. Severe liver failure is uncommon overall, but the risk is much higher in pregnancy, especially late pregnancy. WHO states that up to 20% to 25% of pregnant women may die if infected in the third trimester. There is no specific antiviral that changes the course of ordinary acute hepatitis E. Care is mainly supportive. A vaccine exists and is licensed in China and some other countries, but it is not widely available worldwide.

Key facts

TransmissionMainly faecal-oral transmission through contaminated drinking water; genotypes 3 and 4 can also spread zoonotically, especially through uncooked or undercooked meat and possibly environmental exposure.
Incubation2 to 10 weeks, average 5 to 6 weeks.
Case fatalityAbout 0.5% to 3% in young adults in one 2018 review; WHO states up to 20% to 25% among pregnant women infected in the third trimester. Outbreak CFR varies: for example 0.3% in Chad in 2024 and 5.5% in South Sudan in 2023.
Reproduction numberunknown
VaccineA hepatitis E vaccine is licensed in China and some other countries and has been used in outbreak response, but it is not in broad global use.
TreatmentNo specific antiviral treatment for typical acute hepatitis E; supportive care is standard. Chronic infection in immunosuppressed people has been reported, and ribavirin is discussed in reviews, but WHO says there is no specific antiviral that alters the course of acute disease.
ReservoirHumans for genotypes 1 and 2; non-human mammals for genotypes 3 and 4.
Endemic regionsWorldwide, but most common in sub-Saharan Africa and east and south Asia.

Transmission

Hepatitis E usually spreads by the faecal-oral route. In plain terms, the virus leaves an infected person in stool and reaches another person through contaminated water or food. WHO says this is the main route globally, and it helps explain why outbreaks are often linked to unsafe water, weak sanitation, flooding, and overcrowded camp settings. WHO also notes that genotypes 1 and 2 mainly infect humans and are behind many large waterborne outbreaks in Africa and parts of Asia. Genotypes 3 and 4 are different: they mainly infect animals and can spread to people, especially through uncooked or undercooked meat, with environmental exposure also considered likely. People can shed the virus for days before illness starts and for several weeks after onset. A standard reproduction number is not well established from the sources reviewed here, so it is best described as unknown.

Symptoms and severity

Many infections are mild or cause no obvious symptoms, especially in children in places where hepatitis E is common. When symptoms do happen, WHO lists fever, poor appetite, nausea, vomiting, belly pain, itching, rash or joint pain, jaundice, dark urine, pale stools, and a tender enlarged liver. Symptoms usually last 1 to 6 weeks, and the illness often clears on its own within 2 to 6 weeks. The main danger is rare but serious acute liver failure, sometimes called fulminant hepatitis. Severity is not the same for everyone. A 2018 review reported a case fatality rate of about 0.5% to 3% in young adults, while WHO states that pregnant women, especially in the second or third trimester, face a much higher risk. WHO says up to 20% to 25% of pregnant women may die if infected in the third trimester. Chronic infection can also occur in immunosuppressed people.

Treatment and vaccines

For most people with acute hepatitis E, treatment is supportive. That means rest, fluids, monitoring, and avoiding medicines that can further stress the liver. WHO says there is no specific antiviral treatment proven to alter the course of ordinary acute hepatitis E, and most cases do not need hospital care. Hospital care is important when there are signs of acute liver failure, and WHO says symptomatic pregnant women should also be considered for admission because their risk is higher. A vaccine does exist: WHO states that a hepatitis E vaccine is licensed in China and some other countries and has been used during outbreaks. Still, it is not widely available worldwide, so prevention still depends mainly on safe water, sanitation, hygiene, and food safety. In the research literature, chronic hepatitis E in immunosuppressed people is recognized, and reviews discuss ribavirin use in that setting, but that is not the same as a standard treatment for routine acute infection.

Where it occurs

Hepatitis E is found worldwide, but it is not evenly distributed. WHO says the disease is most common in sub-Saharan Africa and east and south Asia. Large outbreaks are especially associated with places that have limited access to safe drinking water, sanitation, hygiene, and health services. WHO also notes that nearly half of outbreaks occur in camp settings such as refugee camps and camps for internally displaced people. That pattern fits recent outbreak reports on the WHO Disease Outbreak News archive, which include events in Chad, South Sudan, Burkina Faso, Namibia, Nigeria, Niger, Sudan, and earlier Chad notices. In richer countries, the pattern can look different: infections are more often sporadic rather than large waterborne outbreaks, and some are linked to animal reservoirs and food, especially undercooked meat. So the disease is global, but the local risk depends a lot on water systems, sanitation, crowding, and food exposure.

Recent history

On this site, hepatitis E has 11 archived WHO or major-event notices since 1996. The recent pattern is repeated outbreaks in fragile settings rather than one continuous global wave. WHO reported an outbreak in Chad on 2024-05-08: from 2024-01-02 to 2024-04-28, Ouaddai province recorded 2092 suspected cases and 7 deaths, for a reported case fatality ratio of 0.3%. WHO linked the outbreak to displaced populations, crowded camps, and poor water and sanitation conditions. On 2023-05-05, WHO reported an outbreak in Wau, South Sudan, with 91 suspected cases, 35 confirmed cases, and 5 deaths, a reported CFR of 5.5%. Earlier WHO notices document outbreaks or alerts in Chad in 2022 and 2021 South Sudan, Burkina Faso in 2020, Namibia in 2018, Nigeria and Niger in 2017, and Sudan and Chad in 2004. Taken together, the archive shows hepatitis E recurring where water, sanitation, and displacement pressures are severe.

What to watch

The main warning signs are practical public-health signals, not just case counts alone. One is spread into new regions or countries, especially where hepatitis E has been rarely diagnosed before; WHO highlighted this concern in Burkina Faso and Namibia. Another is evidence of wider human-to-human transmission through contaminated shared water in crowded settings, especially camps, conflict zones, or flood-affected areas. A third is rising severity: more deaths overall, more severe disease in pregnant women, or signs of acute liver failure. Fourth, watch for persistent infection in immunosuppressed patients and any sign that usual management is becoming less effective. Last, vaccine access matters. WHO says a vaccine exists and has been used in outbreak response, but it is not broadly available worldwide. If large outbreaks keep occurring while vaccine supply remains limited, that would increase concern. In short, worsening water and sanitation failures, displacement, wider geographic spread, and poor access to prevention tools are the signals to monitor most closely.

Updated