病毒性肝炎主要分为五种，被忽视的最多的就是戊型肝炎。然而，戊型肝炎已经以每年2000万的感染人数席卷全球。绝大多数患者感染戊型肝炎病毒后是没有任何症状的，却每年有56,600个患者因为戊型肝炎病毒及其并发症死亡。

　　戊型肝炎有四种基因型，可以引起急性自限性肝炎。戊型肝炎患者患有潜在的肝部疾病，例如慢性乙型肝炎的感染就会加重肝部疾病。除了患者本身具有的免疫抑制(例如，患者进行过器官移植或是HIV感染者)，急性戊型肝病毒感染者一般不会转变成慢性。感染后还可以引起其他组织器官的疾病，例如，神经系统疾病、胰腺炎、肾损伤和引起血小板减少。

　　这种病毒在亚洲和非洲的发展中国家呈地区性分布，主要以基因1和2型为主，通过粪便或是口鼻传播，例如饮用受污染的水源和母婴垂直传播。戊型肝炎导致了儿童包括2岁以下儿童感染者0.5~4.0%的死亡率，导致了10~25%的孕妇死亡，死亡主要发生妊娠第三个月，表现为暴发性肝衰竭，有出血和子痫的风险。

　　在过去的十年中，人们认为在发达国家患有戊型肝炎是因为患者从疫区生活过。地域性的戊肝病毒现而今也会在发达国家发现，主要受感染者为中老年人，特别是酗酒的人群。比起粪便和口鼻传播，发达国家趋向于动物源性感染的基因3型和4型，主要是未熟的被感染的猪肉 ，还有可能就是因输血而感染。

　　Of the five main forms of viral hepatitis, perhaps the most neglected is hepatitis E virus (HEV). Nevertheless, the virus is one of the most common causes of hepatitis worldwide: an estimated 20 million infections with HEV occur every year. The majority of these infections are asymptomatic, although there are an estimated 3·3 million symptomatic cases and 56?600 HEV-related deaths per year.

　　HEV, of which there are four major genotypes, can cause an acute, self-limiting hepatitis. People with underlying liver disease, such as those with chronic hepatitis B infection, are at risk for exacerbation of their underlying disease if also infected with HEV. Acute HEV infection tends not to develop into a chronic condition except in the immunosuppressed (eg, organ transplant recipients, HIV-infected individuals). Infection with HEV also causes potentially severe extrahepatic manifestations such as neurological symptoms, pancreatitis, kidney injury, and thrombocytopenia. The virus is endemic to regions of Asia and Africa; in developing countries, genotypes 1 and 2 are predominantly spread by the faecal–oral route, mainly by ingestion of contaminated water, although vertical or perinatal transfer from mother to child also occurs. In these areas, HEV primarily affects young adults, with an overall mortality of 0·5–4·0%, increasing in young infants (<2 years). Mortality peaks at 10–25% in pregnant women, particularly those in the third trimester, where women are at risk for fulminant hepatic failure and obstetric complications such as haemorrhage and eclampsia.

　　The perception that HEV infections in developed countries were limited to people returning from travelling in endemic regions has changed over the past decade. Autochthonous HEV is now recognised to occur in developed countries, mainly affecting middle-aged or elderly men, particularly those with high alcohol consumption. Rather than faecal–oral transmission, infection in developed countries tends to occur as a result of zoonosis of genotypes 3 and 4, being transmitted via poorly cooked contaminated food, predominantly pork. Infection can also occur via parenteral transmission by transfusion of blood products.