How is Hepatitis E Transmitted?

Hepatitis E virus (HEV) is an RNA virus with fecal-oral transmission. It is the only member of the hepevirus genus of the family Hepeviridae. At the moment 4 genotypes of the virus (1-4) and up to 24 subtypes have been described. It has not been possible to demonstrate a clear association of the genotype with the clinical manifestations although it seems that genotypes 1 and 2 only produce infections in humans while genotypes 3 and 4 can infect humans and animals. Genotype 3 of HEV has been associated with lower virulence.

It is similar to the hepatitis A virus (HAV), although it seems that the latter has a wider global distribution and produces a greater number of infections. However, it is possible that the HEV is more widely distributed in Western countries than has been described so far.

The highest incidence of HEV infection occurs in Asia, Africa, the Middle East and Central America.

It is transmitted in endemic areas by the ingestion of water with fecal contamination. Transmission between people is infrequent. It can also be transmitted by transfusion and by consuming products from infected animals that have not been properly cooked. The infection can also be transmitted from the infected mother to the newborn (perinatal transmission).

It usually produces a self-limited acute infection although fulminant hepatitis can also develop (with a mortality rate between 0.5 and 3%). Fulminant hepatic failure is more frequent in pregnant women, and in these cases a mortality rate of 25% can be reached, mainly in women in the first trimester of pregnancy. Fulminant hepatitis is also more common in patients with malnutrition or with underlying liver disease

The incubation period of the infection ranges between 15 and 60 days. The symptoms are similar to those seen with other acute viral hepatitis although they may be more severe than with HAV infection. Prolonged cholestasis (stopping of the flow of bile to the duodenum) has been described in up to 60% of those infected with HEV and, in addition to typical symptoms (jaundice, fever, vomiting, abdominal pain, hepatomegaly), symptoms such as arthralgia (joint pain), diarrhea and a urticarial rash have been less frequently reported.

After acute infection, patients do not develop chronic hepatitis except in some special situations. Chronic infection (persistence of elevated levels of liver enzymes, detection of HEV RNA in serum, compatible histological changes with chronic viral hepatitis, and absence of other viral infections) has been described in solid organ transplant patients. Although the natural history of chronic infection in transplant patients is not fully understood, it is usually accompanied by progressive disease and cases of evolution to cirrhosis have been described. Patients with chronic HEV infection have a risk of reactivation, although this seems to be infrequent. Immunosuppression, in general, could predispose to chronic infection and isolated cases by other causes have also been described.

The diagnosis is based on the detection of the virus in serum or feces with PCR techniques or in the detection of IgM antibodies against HEV. The virus can be detected in feces from one week before the clinic starts and can persist for weeks.

In most patients, the period of viremia is usually short, although it may persist for several months. IgM against HEV appears early in serum and disappears after 4-5 months, while IgG titers increase progressively and may remain positive for more than 10 years.

It must be kept in mind that serological tests have been associated with false positives and false negatives with some frequency.

The treatment of the infection is supportive although there are isolated cases that suggest a possible benefit with the use of ribavirin in chronic infection.

Fecal-oral route is the main way of Hepatitis E transmission. Other transmission routes have also been observed, but they only explain a much smaller number of cases: the ingestion of undercooked meat or meat products derived from infected animals, the transfusion of infected blood product and the vertical transmission of a pregnant woman to the fetus.

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