HEPATITIS E VIRUS - detection from blood

HEPATITIS E VIRUS (HEV)

KEY FACTS:

HEV infection causes inflammation of the liver. 

Transmission: fecal-oral route, especially contaminated water. HEV: found worldwide; most common East and South Asia. 

OVERVIEW:

HEV has 4 different types: genotypes 1, 2, 3 and 4. Genotypes 1 and 2: only in humans; genotypes 3 and 4: in pigs, wild boars and deer without causing any disease, and occasionally infect humans. 

The virus: shed in the stools of infected persons; enters the human body through the intestine. It is transmitted mainly through contaminated drinking water. The infection is usually self-limiting and resolves within 2-6 weeks. Occasionally leads to fulminant hepatitis (acute liver failure); it can be fatal. 

TRANSMISSION:

HEV infection is found worldwide, but common in low- and middle- income countries with limited access to essential water, sanitation, hygiene and health services. Here, it occurs both as outbreaks and as sporadic cases. The outbreaks follow periods of faecal contamination of drinking water supplies. Sporadic cases are also believed to be related to contamination of water, albeit at a smaller scale. The cases in these areas are caused mostly by infection with genotype 1 virus, and much less frequently by genotype 2 virus. In areas with better sanitation and water supply, HEV infection is infrequent, with only occasional sporadic cases. Most of these cases are caused by genotype 3 virus and are triggered by infection with virus originating in animals, usually through ingestion of undercooked animal meat.

SYMPTOMS:

Incubation period: 2-10 weeks (5-6 weeks average). The infected persons excrete the virus beginning from a few days before to 3-4 weeks after onset. Typical sings and symptoms: 

- initially: mild fever, reduced appetite (anorexia), nausea and vomiting (a few days);

- abdominal pain, itching, skin rash, or joint pain;

- jaundice, dark urine and pale stools;

- enlarged, tender liver (hepatomegaly)

These symptoms typically last 1-6 weeks. 

Rarely, acute hepatitis E can be severe and results in fulminant hepatitis (acute liver failure) - risk of death. Cases of chronic HEV infection: in immunosuppressed people, particularly organ transplant recipients on immunosuppressive drugs, with genotype 3 or 4 HEV infection (uncommon). 

DIAGNOSIS:

Hepatitis E cases: not clinically distinguishable from other acute viral hepatitis. However, diagnosis can often be strongly suspected when for example several cases occur in localities in known disease-endemic areas, 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 HEV infection is usually based on the detection of specific anti-HEV immunoglobulin M (IgM) antibodies in a person's blood. Rapid tests are available for field use. Additional tests: reverse transcriptase polymerase chain reaction (RT-PCR) to detect the HEV RNA in blood and stool.

TREATMENT:

As the disease is usually self-limiting, hospitalization is generally not required. Acetaminophen, paracetamol and medication against vomiting should be used sparingly. Hospitalization: required for fulminant hepatitis and symptomatic pregnant women. For immunosuppressed people with chronic hepatitis E: ribavirin treatment. In some specific situations, interferon has also been used successfully. 

PREVENTION:

At the population level, HEV transmission and infection  can be reduced by: 

- maintaining quality standards for public water supplies;

- establishing proper disposal systems for human faeces.

On an individual level, infection risk can be reduced by: 

- maintaining hygienic practices;

- avoiding consumption of water and ice of unknown purity.