Hepatitis E

Hepatitis E is a viral hepatitis (liver inflammation) caused by infection with a virus called hepatitis E virus (HEV). Infection with this virus was first documented in 1955 during an outbreak in New Delhi, India.^[1]

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Signs and symptoms

• Prolonged cholestasis has been described in up to 60 percent of patients.^[2]
• Jaundice
• Malaise
• Anorexia
• Nausea
• Vomiting
• Abdominal pain
• Fever
• Hepatomegaly
• Other less common features include diarrhea, arthralgia, pruritus, and urticarial rash. Some patients have asymptomatic infection.

Virology

The viral particles are 27 to 34 nanometers in diameter, are non-enveloped and contain a single-strand of positive-sense RNA that is approximately 7300 bases in length. The virus particle was first visualised in 1983^[3] but was only molecularly cloned in 1990.^[4]

It was previously classified family Caliciviridae. However, its genome more closely resembles the rubella virus. It is now classified in a new virus family, named as Hepeviridae.

Epidemiology

The incidence of hepatitis E is highest in adults between the ages of 15 and 40. Though children often contract this infection as well, they less frequently become symptomatic. Mortality rates are generally low, for Hepatitis E is a “self-limiting” disease, in that it usually goes away by itself and the patient recovers. However, during the duration of the infection (usually several weeks), the disease severely impairs a person’s ability to work, care for family members, and obtain food. Hepatitis E occasionally develops into an acute severe liver disease, and is fatal in about 2% of all cases. Clinically, it is comparable to hepatitis A, but in pregnant women the disease is more often severe and is associated with a clinical syndrome called as 'fulminant hepatic failure'. Pregnant women, especially those in the third trimester, suffer an elevated mortality rate from the disease ~20%.

Patterns

Hepatitis E is prevalent in most developing countries, and common in any country with a hot climate. It is widespread in Southeast Asia, northern and central Africa, India, and Central America. It is spread mainly through fecal contamination of water supplies or food; person-to-person transmission is uncommon. Outbreaks of epidemic Hepatitis E most commonly occur after heavy rainfalls and monsoons because of their disruption of water supplies. Major outbreaks have occurred in New Delhi, India (30,000 cases in 1955-1956), Burma (20,000 cases in 1976-1977), Kashmir, India (52,000 cases in 1978), Kanpur, India (79,000 cases in 1991), and China (100,000 cases between 1986 and 1988).

Animals as a reservoir

Domestic animals have been reported as a reservoir for the hepatitis E virus, with some surveys showing infection rates exceeding 95% among domestic pigs.^[5] Transmission after consumption of wild boar meat and uncooked deer meat has been reported as well.^[6] The rate of transmission to humans by this route and the public health importance of this are however still unclear. Rats also carry the virus.^[7]

Recent outbreaks

In 2004, there were two major outbreaks, both of them in sub-Saharan Africa. There was an outbreak in Chad in which, as of September 27 there were 1,442 reported cases and 46 deaths. In Sudan, which has been troubled with conflict recently (see, Darfur conflict), they are also suffering from a severe Hepatitis E epidemic. As of September 28, there were 6,861 cases and 87 deaths, mainly in the West Darfur Region. UNICEF, Doctors Without Borders, the Red Cross, and other international health organizations are currently working to increase the availability of soap, dig new wells, and chlorinate water supplies and reserves. However, the existing resources are still not enough, and more personnel and funds are severely needed in the region to assure the health and welfare of the people. Increasingly, hepatitis E is being seen in developed nations with reports of cases in the UK, US and Japan. The disease is thought to be a zoonosis in that animals are thought to be the source. Both deer and pigs have been implicated.

Prevention

Improving sanitation is the most important measure, which consists in proper treatment and disposal of human waste, higher standards for public water supplies, improved personal hygiene procedures and sanitary food preparation. Thus, prevention strategies of this disease are similar to those of many others that plague developing nations, and they require large-scale international financing of water supply and water treatment projects. A vaccine based on recombinant viral proteins has been developed and recently tested in a high-risk population (military personnel of a developing country).^[8] The vaccine appeared to be effective and safe, but further studies are needed to assess the long-term protection and the cost-effectiveness of hepatitis E vaccination.

References