Infection is caused by hepatitis E virus (HEV), a single-stranded, RNA virus belonging to the Hepeviridae family.
HEV is transmitted primarily by the fecal-oral route. In regions with poor sanitation and limited access to safe drinking water, epidemics and interepidemic occurrences of hepatitis E are largely waterborne. Transmission to fetuses and neonates by women infected during pregnancy is common. In Japan and Europe, sporadic disease can be zoonotic and foodborne, associated with eating meat and offal (including liver) of deer, boars, and pigs. In France, disease can be acquired from eating figatellu, a sausage delicacy prepared from raw pig liver. Sporadic disease also is observed in the United States and other temperate countries, but its cause is generally unknown. Shellfish can transmit HEV. Transmission from blood transfusion has been reported, although rare.
Waterborne outbreaks (which can be large, involving hundreds to thousands of people) have occurred in South and Central Asia, tropical East Asia, Africa, and Central America (Map 3-06). Of note, Hong Kong SAR and Singapore have been identified as endemic areas. Clinical attack rates are highest in young adults aged 15–49 years. In outbreak-prone areas, interepidemic disease is sporadically encountered. In these areas, pregnant women—whether infected sporadically or during an epidemic—are at risk of their HEV disease progressing to liver failure and death. Miscarriages and neonatal deaths are common complications of HEV infection.
Sporadic disease also occurs in regions that are not prone to outbreaks, such as the Middle East, temperate East Asia (including China), North and South America, and Europe. Symptomatic disease is observed most frequently in adults aged >50 years. Primary infection acquired by people who are immunosuppressed, particularly recipients of solid-organ allografts, may progress to chronic infection.
People living in the United States are at risk of HEV infection when they travel to areas where epidemics have occurred. When traveling in Japan and Europe, eating raw or inadequately cooked venison, boar meat, pig liver, pig meat, or food products derived from these is a risk factor for infection.
Map 3-06. Distribution of hepatitis E virus infection1
1Disease data adapted from: World Health Organization. The Global Prevalence of Hepatitis E Virus Infection and Susceptibility: A Systematic Review. http://whqlibdoc.who.int/hq/2010/WHO_IVB_10.14_eng.pdf. Accessed November 13, 1024. 2Defined as waterborne outbreaks or confirmed Hepatitis E virus infection ≥25% of sporadic non-A, non-B hepatitis 3Defined as confirmed Hepatits E virus infection in <25% of sporadic non-A, non-B hepatits
The incubation period of acute hepatitis E is 2–9 weeks (mean 6 weeks). Signs and symptoms of disease during acute infection include jaundice, fever, loss of appetite, abdominal pain, and lethargy. A wide range of neurologic manifestations have been associated with HEV. For most people, HEV infection and disease is self-limited. Pregnant women (especially those infected during the second or third trimester) may present with or progress to liver failure, and their fetuses are at risk of spontaneous abortion and premature delivery. People with preexisting liver disease may undergo further hepatic decompensation with HEV infection. Recipients of organ transplants tend to have no symptoms associated with acute and chronic HEV infection.
The diagnosis of acute hepatitis E is established by detecting anti-HEV IgM and IgG in serum. Detecting HEV RNA in serum or stools further confirms the serologic diagnosis but is seldom required. Longer-term, serial detection of HEV RNA in serum or stools, regardless of the HEV antibody serostatus, suggests chronic HEV infection. No diagnostic test for HEV has been approved by the Food and Drug Administration.
Treatment is supportive. Oral ribavirin has been used to treat chronic hepatitis E in solid-organ transplant recipients.
No vaccine is available, nor are drugs for preventing infection. Travelers should avoid drinking unboiled or unchlorinated water and beverages that contain unboiled water or ice. Travelers should eat only thoroughly cooked food, including seafood, meat, offal, and products derived from these (see Chapter 2, Food & Water Precautions).