Hepatitis is an inflammation of the liver due to infections, alcohol, drugs, or autoimmune diseases. There are five hepatitis viruses: hepatitis A, B, C, D, and E. Many people also refer to these viruses as HAV, HBV, HCV, HDV, and HEV, respectively. Hepatitis E is a widespread condition occurring in developing countries that lack clean water and adequate environmental sanitation. Asia, Africa, the Middle East, Central America, and Mexico have experienced outbreaks. It is uncommon for physicians to diagnose HEV in developed countries unless the patient has recently traveled to a developing country.

Definition of Hepatitis E

A single-stranded RNA virus -- the hepatitis E virus  -- causes the condition. According to the World Health Organization, more than 20 million people experience HEV infections around the world every year. The most common source for transmission is contaminated drinking water. HEV enters the body through the intestine and exits through the stools of those infected. It generally goes away on its own within two to six weeks. Patients usually do not experience complications and mortality is low. However, some patients with hepatitis E can develop a more serious condition that causes acute liver failure (ALF), which can be fatal.

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The Unique Characteristics of HEV

Researchers have identified four genotypes of hepatitis E that cause illness in humans, but each has different epidemiological and clinical characteristics and are unlike any other types of hepatitis. These differences vary between countries. Asia and Africa report large outbreaks of genotype 1 transmitted through water or poor sanitation. Medical researchers found sporadic genotype 2 infections in Mexico and West Africa. Refugee camps or overcrowded housing situations near natural disasters are at-risk locations for HEV. China, Taiwan, Japan, and Europe experience mostly food-borne genotype 4, but outbreaks do not usually occur. People contract genotype 3 from food and it occurs in isolated cases in developed countries.

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Transmission of Hepatitis E

HEV genotypes 1 and 2 affect only humans, primarily through fecally contaminated water. Epidemics of acute HEV-associated hepatitis occur in developing areas, along with ongoing infections transmitted through contaminated groundwater. Medical professionals blame contaminated food for outbreaks of genotypes 3 and 4 in developing nations, with sporadic cases in developed countries as well. Transmission of HEV through blood transfusions occurs in countries where the infection is prevalent among the general population. Research shows no evidence that individuals can contract hepatitis E by sharing needles or through sexual contact, although there is a risk with oral-anal contact.

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Animal Transmission of Hepatitis E

Researchers identified hepatitis E genotypes 3 and 4 in boar, deer, and pork meat, linking the transmission of the virus through food. This would most likely occur in sporadic cases involving contaminated, uncooked, or undercooked meat or organs. Individuals who handled, processed, and consumed deer meat account for a percentage of these HEV infections. There have been studies linking the transmission of HEV infections from domestic pigs to those who work with them occupationally. Researchers say the human and swine strains of HEV are closely related. Shellfish and rodents in some areas may also be capable of HEV transmission. But researchers also found other animal species that carry anti-HEV antibodies, including cows, horses, sheep, rabbits, and avian species.

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Symptoms of Hepatitis E

Symptoms associated with hepatitis E are similar to other types of hepatitis. Individuals who contract hepatitis E usually have a fever and report an overall feeling of discomfort, illness, and fatigue. Additionally, they experience jaundice, a yellowing of the skin or whites of the eyes that generally indicates liver issues. Anorexia, nausea, and vomiting are also symptoms. Some individuals report abdominal and joint pain as well. Upon examination, doctors find a slightly enlarged, tender liver. Dark urine and pale stools are also hepatitis E symptoms. Nearly 28 percent of pregnant women with hepatitis E are anemic, according to a study published by the American Society of Tropical Medicine and Hygiene.

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Higher Risk Groups

In developing countries, people between the ages of 15 and 44 appear to be at greater risk for contracting hepatitis E. Those with preexisting liver conditions are more susceptible to serious complications. Doctors consider pregnant women with hepatitis E to be a high-risk group for developing a serious, life-threatening illness. This illness, fulminant hepatitis, is a rare syndrome featuring a decrease in liver size. According to research statistics, around 30 percent of pregnant women who contract hepatitis E die from it. Malnutrition may also play a role in hepatitis E infections.

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Incubation and Infectiousness

Symptoms for hepatitis E usually develop between 15 and 60 days after exposure. Most symptoms continue for one to six weeks after infection. However, studies have found cases where symptoms persisted for up to ten weeks. Within the first few days and up to three or four weeks following the onset of hepatitis E, infected individuals begin to excrete the virus through their stools. Infected persons remain infectious from onset up to 30 days, although research has not revealed specific periods of infectiousness.

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Diagnosis is challenging if the patient has not traveled to or resided in an area with a high prevalence of infection because hepatitis E is not distinguishable from other forms of viral hepatitis. Where available, doctors perform tests to determine the presence of IgM antibodies to the virus in the patient’s blood. Additional testing includes RT-PCR, used to detect hepatitis E virus RNA in the stool or blood. Although the FDA has not yet approved testing methods for hepatitis E in the U.S., commercial research laboratories are performing serologic testing. Ongoing research continues for effective methods of diagnosis.

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Increased Chronic HEV Infections Within Specific Populations

In recent years, medical communities are reporting an increasing number of hepatitis E cases that progressed to chronic hepatitis and chronic liver disease, according to the Centers for Disease Control. Many of these cases occurred among patients with genotype 3 infections who were receiving immunosuppressive treatments for an organ transplant. Treatment included lowering the dosage of these medications, which helped clear the infection. Additionally, doctors have diagnosed chronic HEV infections in patients with a hematological disease and in HIV-positive patients. Physicians treating these patients with antiviral therapies have found success in clearing the infections as well.

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Prevention and Treatment

There currently is no vaccine available in the U.S. to prevent hepatitis E, though there are vaccines that are under development in some parts of the world. The best prevention is good sanitation practices. Clean drinking water is imperative. For those who travel to areas of the world where HEV infections are prevalent, experts advise drinking only purified water. People in both developed and developing countries should avoid undercooked pork and be cautious when handling and preparing deer meat. Individuals who work closely with animals including veterinarians and butchers should take precautionary measures to prevent infection.

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