- Hepatitis E is a liver disease caused by infection with a virus known as hepatitis E virus (HEV).
- Every year, there are an estimated 20 million HEV infections worldwide, leading to an estimated 3.3 million symptomatic cases of hepatitis E (1).
- WHO estimates that hepatitis E caused approximately 44 000 deaths in 2015 (accounting for 3.3% of the mortality due to viral hepatitis).
- The virus is transmitted via the fecal-oral route, principally via contaminated water.
- Hepatitis E is found worldwide, but the disease is most common in East and South Asia.
- A vaccine to prevent hepatitis E virus infection has been developed and is licensed in China but is not yet available elsewhere.
Hepatitis E is a liver disease caused by the hepatitis E virus (HEV). The virus has at least 4 different types: genotypes 1, 2, 3 and 4. Genotypes 1 and 2 have been found only in humans. Genotypes 3 and 4 circulate in several animals (including pigs, wild boars, and deer) without causing any disease, and occasionally infect humans.
The virus is shed in the stools of infected persons, and enters the human body through the intestine. It is transmitted mainly through contaminated drinking water. Usually the infection is self-limiting and resolves within 2–6 weeks. Occasionally a serious disease, known as fulminant hepatitis (acute liver failure) develops, and a proportion of people with this disease can die.
Symptoms
The incubation period following exposure to HEV ranges from 2 to 10 weeks, with an average of 5 to 6 weeks. The infected persons excrete the virus beginning from a few days before to 3-4 weeks after onset of the disease.
In areas with high disease endemicity, symptomatic infection is most common in young adults aged 15–40 years. In these areas, although infection does occur in children, they often have either no symptoms or only a mild illness without jaundice which goes undiagnosed.
Typical signs and symptoms of hepatitis include:
- an initial phase of mild fever, reduced appetite (anorexia), nausea and vomiting, lasting for a few days; some persons may also have abdominal pain, itching (without skin lesions), skin rash, or joint pain.
- jaundice (yellow colour of the skin and whiteness of the eyes), with dark urine and pale stools; and
- a slightly enlarged, tender liver (hepatomegaly).
These symptoms are often indistinguishable from those experienced during other liver illnesses and typically last 1–6 weeks.
In rare cases, acute hepatitis E can be severe, and result in fulminant hepatitis (acute liver failure); these patients are at risk of death. Fulminant hepatitis occurs more frequently when hepatitis E occurs during pregnancy. Pregnant women with hepatitis E, particularly those in the second or third trimester, are at increased risk of acute liver failure, fetal loss and mortality. Up to 20–25% of pregnant women can die if they get hepatitis E in third trimester.
Cases of chronic hepatitis E infection have been reported in immunosuppressed people, particularly organ transplant recipients on immunosuppressive drugs, with genotype 3 or 4 HEV infection. These remain uncommon.
Diagnosis
Cases of hepatitis E are not clinically distinguishable from other types of acute viral hepatitis. However, diagnosis can often be strongly suspected in appropriate epidemiologic settings, for example when several cases occur in localities in known disease-endemic areas, or in settings with risk of water contamination, when the disease is more severe in pregnant women, or if hepatitis A has been excluded.
Definitive diagnosis of hepatitis E infection is usually based on the detection of specific IgM antibodies to the virus in a person’s blood; this is usually adequate in areas where disease is common. Rapid tests are available for field use.
Additional tests include reverse transcriptase polymerase chain reaction (RT-PCR) to detect the hepatitis E virus RNA in blood and/or stool; this assay requires specialized laboratory facilities. This test is particularly needed in areas where hepatitis E is infrequent, and in cases with chronic HEV infection.
Treatment
There is no specific treatment capable of altering the course of acute hepatitis E. As the disease is usually self-limiting, hospitalization is generally not required. Most important is the avoidance of unnecessary medications. Acetaminophen/Paracetamol and medication against vomiting should not be given.
However, hospitalization is required for people with fulminant hepatitis, and should also be considered for symptomatic pregnant women.
Immunosuppressed people with chronic hepatitis E benefit from specific treatment using ribavirin, an antiviral drug. In some specific situations, interferon has also been used successfully.
