A viral infection of the liver is most commonly due to one of the five types of hepatitis viruses – A, B, C, D and E. These viruses are similar in structure, except for hepatitis D, and the pathogenesis is also similar. Some are more likely to cause just an acute infection and resolve, while others are often associated with a chronic infection. The risk profiles may vary for the different types of hepatitis due to the mode of transmission. In this regard, hepatitis A and E are more frequently associated with the ingestion of contaminated food or water (orofecal route). Hepatitis B, C and D are transmitted by the sharing of bodily fluids, mainly blood and semen and less frequently saliva.
Of the different types of viral hepatitis, it is hepatitis A, B and C that are most commonly heard of with hepatitis D being seen in about one fourth of all hepatitis B infections. A less frequently heard of viral hepatitis is hepatitis E. This is endemic in certain areas like south and central Asia and is more likely to be observed in travelers to these areas. About half of all acute cases of viral hepatitis contracted by travelers to India is due to the hepatitis E virus (HEV). However, recently the prevalence of this hepatitis E has increased globally although it is still fairly uncommon.
What is hepatitis E?
Hepatitis E is a viral infection of the liver caused by the hepatitis E virus (HEV). It causes acute hepatitis that is self-limiting and does not progress to chronic hepatitis and liver diseases like cirrhosis. However, in pregnant women, HEV infection may lead to the development of acute liver failure and there is a high mortality rate. About 20% of pregnant women with HEV infection will die of acute liver failure.
The hepatitis E virus (HEV) is a calcivirus with a single strand of RNA that is unenveloped. It was identified in he 80s when non-A and non-B hepatitis was investigated further. The hepatitis E virus, like the hepatitis A virus, is transmitted via the orofecal route. During an active infection, the patient sheds virions in the stool and in countries with poor sewage systems, this can easily contaminate drinking water. Water contaminated with fecal particles containing the virus may be drank or consumed in food. HEV is a zoonotic disease because certain animals apart from humans may be reservoirs, including dogs, cats, pigs and monkeys.
Signs and Symptoms of HEV
Hepatitis E is almost never seen in children. Young adults and adults up to the age of 40 years are at the greatest risk. The mean incubation period is between 4 to 6 weeks and the symptoms resolve within 2 to 4 weeks. Hepatitis E is an acute, self-limiting disease with two clinical phases.
Non-specific symptoms include :
- Nausea and vomiting
- Abdominal discomfort or pain
- Joint pains
- Muscle pain
- Loss of appetite
- Weight loss
- Dark urine
- Itchy skin
- Skin rash
- Pale stools
What is Hepatitis G?
The hepatitis G virus (HGV or GBV-C) is a flavivirus that is genetically similar to the hepatitis C virus (HCV) and spread by contact with blood. However, hepatitis G is often not considered with the other five hepatitis viruses because it does not have predilection for the liver and neither does it cause an elevation of the liver enzymes as is the case with the other hepatitis viruses. HGV targets the bone marrow and spleen and replicates at these site. It does not appear to cause any known human disease. Co-infection is possible and occasionally seen with hepatitis B and hepatitis C but unlike the hepatitis D virus, this is not essential for the replication of HGV.
Other Viruses That Cause Hepatitis
The liver is prone to various viral infections, as is the case with other organs. These other viruses are not specific for the liver as is the case with the hepatitis viruses. These other viruses are sometimes termed non-A, non-B, non-C (NANBNC) in reference to absence of the more common hepatitis viruses – HAV, HBV and HCV.
Some of these other viruses includes :
- Cytomegalovirus (CMV)
- Epstein-Barr virus (EBV)
- Herpes simplex (HSV)
These viral infections of the liver are more frequently seen in immunocompromised patients. Abnormal liver function tests (LFTs) may also be seen with other viral infections like chickenpox, rubella, measles and in acute HIV infection despite the lack of liver-specific symptoms like jaundice.