What is Hepatitis E or ET-Non A Non B Hepatitis and its Epidemiological features?

Hepatitis E or Enterically transmitted Non A Non B (ET-Non A Non B) heptitis is a viral infection commonly caused by use of contaminated drinking water with sewage through faeco-oral route and person to person among household contacts. It is the most common cause of Hepatitis in the South East Asia & the Indian subcontinents.It occurs in two epidemiological forms,the epidemic and the sporadic hepatitis.

Hepatitis E or Enterically transmitted Non A Non B Hepatitis

Hepatitis E is an enterically transmitted Non A Non B hepatitis (ET-NA NB) virus. It is a viral infection commonly caused by use of contaminated drinking water with sewage through faeco-oral route and person to person among household contacts. It is the most common cause of hepatitis in the South-East Asia and the Indian sub-continent. This disease occurs in two epidemiological forms, the epidemic form & the sporadic form of hepatitis.

Hepatitis E in India :

This infection is responsible for the most of epidemics of viral hepatitis occurring in India. The first recorded epidemic of this infection occurred in Delhi from December 1955 to January, 1956. Heavy rain fall in October, 1955 lead to flood in river Yamuna which flows through the city. There was total contamination of water of one pumping station of the city from a large, open drain from 10th to 17th November, 1955. Epidemic of hepatitis starts in the city in the 1st week of December. The disease appears with following symptoms:
• Anorexia
• Nausea
• Vomiting and
• Abdominal pain & discomfort followed by
• Appearance of dark coloured urine and
• Jaundice.

More than 29,000 populations develop clinical symptoms of disease. The epidemic reached its peak in about a fortnight and become less active quickly within one and half months of its onset. Only about 2.5% of people using polluted water are affected by hepatitis while those receiving water from other sources, the frequency of jaundice during this period was only 0.35% which was quite less.
• Incubation Period of hepatitis in this epidemic ranges from 22 to 60 days.
• The incidence rate of disease is highest in the age group from 15 to 39 years
• Both sexes are affected equally.
• The disease is often benign and self limiting.
• Case fatality rate is 10% in pregnant females due to Fulminant hepatic failure.
• Women in 3rd trimester of pregnancy were especially vulnerable.

The epidemic was initially believed to be due to Hepatitis A Virus but in 1980,when a stored serum samples were tested serologically for HAV & HBV infections, it was found that the epidemic is due to Enterically Transmitted non A, non B hepatitis viruses.
Other similar epidemics recorded in different parts of India at different times in Ahmedabad (1975-76) and in Baramulla district in Kashmir (1980). It has been established that hepatitis E or enterically transmitted non-A, non-B virus was responsible for 9 out of 10 epidemics of hepatitis in our country. All these epidemics are very similar to that of Delhi epidemic

Epidemiological features of Hepatitis E :

Hepatitis E or ET- Non A Non B epidemic in India and other developing countries, infection spread from person to person where sanitary condition is poor with unprotected water supply. Hepatitis E infection is also facilitated in people with low socio-economic status and poor personal hygiene resulting faecal contamination (only route of infection).In certain geographical areas Non A Non B infection is reported in endemic form with seasonal outbreaks. Epidemic mostly occur 97% in developing countries of South East Asia as compared to developed Western countries. The ende- micity of this disease is not known. Travellers from endemic areas Non A Non B or people from epidemic area acts as carrier to the western countries.
It has been observed that the peak of epidemic occurs in a susceptible geographic area around 6 weeks after infection of disease. Majority of population is at risk between the ages of 20 to 40 years. The disease is rare in extreme of age. Children of school going age and below do not develop the signs and symptoms of disease (they are in sub-clinical state). Pregnant females show clinical picture with 9% incidence of Fulminant Liver Failure as compared to non pregnant females up to 3%.

Clinical features of ET-NA NB Viral Hepatitis :

• Clinical features of enterically transmitted non A non B hepatitis resembles to infectious hepatitis (hepatitis A) like anorexia, nausea, vomiting, abdominal pain & discomfort followed by appearance of dark coloured urine and jaundice.
• Incubation period of disease is between 2 to 9 weeks. The incubation period of shorter duration is seen in the epidemics.
• Attack rate is highest between 15-40 years of age
• Sub-clinical infection observed in children with changed enzyme values
• Chronic liver disease or viraemia is not seen
• High percentage of death is seen in pregnant females due to cytokines.

Diagnosis of Hepatitis E :

Laboratory diagnosis is established by serological examination (serology) by exclus-ion of Hepatitis A, B, C and D infections. Diagnosis of Hepatitis E is done by seeing the virus like particles (VLPs) in the stool of patient. This test is done within 5 days of the starting of prodromal symptoms by immune Electron microscopy. Two types of virus like particles (VLPs) are seen in ET-NA NB infection. The size of larger particle is between 32-34 nm and that of an incomplete virus particle is of 27-30 nm size. Two types of histological changes occur in human patients of ET-NA NB namely
• Degenerative changes
• Necro-inflammatory changes
Degenerative changes occur with acidophilic degeneration and coagulation type of liver cell necrosis with highest values. The nuclei of these cells are like Pyknotic & nuclear chromatin remnants disperse all over and appear as acidophilic bodies. Liver cell necrosis is generalised in fulminant hepatic failure patients, or it may be spotty in case of mild infection.
The characteristic features under microscope are prominent intra-lobular histocytic inf-fileration with scanty lymphocytes although collection of mononuclear cells and macrophages are seen in sinusoidal lumen.

Characteristic features of Virus like Particles (VLPs) in Hepatitis E infection:
In the stool of hepatitis E (Non A Non B) patients, presence of VLPs were reported in the early 80's of 19th century. In 1982-83 it was found that these VLPs have a constant size ranges 27-34nm is very much smaller than hepatitis B & hepatitis C virus infection. They are extremely sensitive calcium chloride & could be changed in character by freezing and heating. Pelleting stools completely loose VLPs and only few incomplete VLPs could be seen under electron microscope. Bile of gall bladder is richest source of VLPs. The virus like particles possesses single stranded undeveloped RNA.

Serology pf ET-Non A Non B VLPs :

The individuals who are infected by this virus develops a vigorous active phase antibody response but fails to develop high affinity antibody titre seen in other viral hepatitis infections.

Prevention of Hepatitis E :

There is no specific treatment of disease. It can only be prevented by proper sanitation of sewage and protected water supply for drinking purposes. Immuno-prophylaxis by immunoglobin may be useful in pregnant females.


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