Kolkata: Hepatitis E is a liver disease caused by infection with a virus known as hepatitis E virus (HEV): a small virus, with a positive-sense, single-stranded ribonucleic acid (RNA) genome.
According to the World Health Organization report, every year, there are an estimated 20 million HEV infections worldwide, leading to an estimated 3.3 million symptomatic cases of hepatitis E.The virus has at least 4 different types: genotypes 1, 2, 3 and 4. Genotypes 1 and 2 have been found only in humans. Genotype 3 and 4 viruses 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.
Hepatitis E infection is found worldwide. Two different patterns are observed, where hepatitis E is found in: resource-poor areas with frequent water contamination and areas with safe drinking water supplies.The disease is common in resource-limited countries with limited access to essential water, sanitation, hygiene and health services. In these areas, the disease occurs both as outbreaks and as sporadic cases. The outbreaks usually follow periods of faecal contamination of drinking water supplies and may affect several hundred to several thousand persons.
Some of these outbreaks have occurred in areas of conflict and humanitarian emergencies, such as war zones, and in camps for refugees or internally displaced populations (IDP), situations where sanitation and safe water supply pose special challenges.Sporadic cases are also believed to be related to contamination of water or food, 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, hepatitis E disease is infrequent with only occasional sporadic cases. Most of these cases are caused by genotype 3 virus, and are caused by infection with virus originating in animals, usually through ingestion of undercooked animal meat (including animal liver) and are not related to contamination of water or other foods.
Serological evidence of prior exposure to the virus has been found in most areas, with higher seroprevalence rates (proportion of people who test positive for IgG antibodies to HEV) in regions with lower standards of sanitation and thus higher risk for transmission.
However, presence of these antibodies does not imply presence of or increased risk of disease. The usefulness of such data for epidemiological purposes may also be limited due to variable and possible sub-optimal performance of available serological assays, and possible disappearance of the antibody with the passage of time among those exposed to the virus.