Hepatitis E

Hepatitis E is inflammation of the liver resulting from infection with the hepatitis E virus (HEV), recognized as the fifth form of viral hepatitis ^[1][2]. The virus is excreted in stool and enters the body through the oral route ^[1].

The incubation period after exposure ranges from 2 to 10 weeks, averaging 5 to 6 weeks, and viral shedding begins a few days before to several weeks after symptom onset ^[1][2]. Most infections are asymptomatic with spontaneous viral clearance, but a self-limiting hepatitis may occur and occasionally progresses to fulminant hepatitis or acute liver failure ^[1][3]. In endemic areas, symptomatic disease is most common among young adults aged 15–40 years, while children often have mild or silent illness ^[1].

Hepatitis E occurs worldwide and is especially common in low- and middle-income countries with poor water, sanitation, and hygiene services, appearing as both outbreaks and sporadic cases ^[1][2]. HEV genotypes 1 and 2 predominate in developing regions and drive large waterborne outbreaks, whereas genotypes 3 and 4 are encountered mainly in developed countries with zoonotic transmission ^[1][2][3]. Approximately 20 million infections occur annually, and in high-endemicity settings symptomatic infection concentrates in young adults ^[1][3]. Outbreaks have affected conflict and humanitarian emergency settings where safe water is limited ^[1].

HEV is shed in feces and primarily enters humans via the oral route, mainly through contaminated drinking water in a fecal–oral manner ^[1]. Genotypes 1 and 2 spread chiefly among humans through contaminated water, while genotypes 3 and 4 are mainly zoonotic, transmitted by consumption of undercooked meat and likely environmental exposure ^[1][2][3].

Prevention of hepatitis E centers on avoiding transmission routes identified in the evidence. Since genotypes 1 and 2 are mainly faecal-orally transmitted via contaminated drinking water, especially in low- and middle-income countries with limited water, sanitation and hygiene access, ensuring safe water and sanitation is critical ^[1]. Genotypes 3 and 4 are mainly zoonotic, transmitted through consumption of uncooked or undercooked meat, indicating that proper cooking of meat is a relevant preventive measure ^[1]. For outbreak response, a hepatitis E vaccine was approved under the International Coordinating Group mechanism and WHO is working to make it available as an outbreak response intervention; WHO also issued guidance in 2014 on recognition, investigation and control of waterborne outbreaks ^[1].

1. 1 World Health Organization. Hepatitis E [Internet]. cited 3 Sept 2026. Available from: https://www.who.int/news-room/fact-sheets/detail/hepatitis-e
2. 2 Aslan AT et al. Hepatitis E virus: Epidemiology, diagnosis, clinical manifestations, and treatment. World J Gastroenterol. 2020 Oct 7. PMID: 33071523. doi: 10.3748/wjg.v26.i37.5543. PubMed: https://pubmed.ncbi.nlm.nih.gov/33071523/
3. 3 Songtanin B et al. Hepatitis E Virus Infections: Epidemiology, Genetic Diversity, and Clinical Considerations. Viruses. 2023 Jun 17. PMID: 37376687. doi: 10.3390/v15061389. PubMed: https://pubmed.ncbi.nlm.nih.gov/37376687/