Viral hepatitis is an important cause of morbidity and mortality worldwide. It can result in acute hepatitis, chronic liver disease, and hepatocellular carcinoma. A number of DNA viruses are associated with viral hepatitis. These include the hepatitis B virus, the hepatitis C virus, and the hepatitis E virus.
Hepatitis B virus (HBV) is a small DNA virus that can cause viral hepatitis. It is most commonly spread from mothers to infants during pregnancy (perinatal transmission) or through horizontal transmission (exposure to infected blood).
Infection with hepatitis B can lead to serious liver disease and even liver cancer. Chronic hepatitis B infection can go unnoticed for decades until a person develops liver problems like cirrhosis or liver failure.
Hepatitis B virus enters the cell by binding to a special protein on the surface of the cell called nucleotide transfer protein (NTP). Once inside the cell, a hepatitis B virus DNA polymerase incorporates its pre-genomic RNA into the capsid. The pgRNA undergoes reverse transcription to make the (+) DNA strand. It is then converted to covalently closed circular DNA (cccDNA). This cccDNA serves as the template for viral mRNA production by a host RNA polymerase. The hepatitis B virus then replicates and infects new cells, producing more virus particles.
Hepatitis C is caused by the Hepatitis C virus (HCV). This single-stranded RNA virus is spread through blood-to-blood contact.
A speck of blood, invisible to the naked eye, can carry hundreds of HCV particles. In most cases, hepatitis C is transmitted through needlestick exposures or other blood-related equipment used to prepare or inject drugs.
The hepatitis C virus can also be passed from an infected mother to her baby during pregnancy or from blood-to-blood contact during sex. These modes of transmission are less common.
The hepatitis C virus is a major cause of liver disease and can lead to life-threatening health problems such as liver failure, cirrhosis, and cancer. It is highly treatable with antiviral medicines. However, access to diagnosis and treatment is limited.
Hepatitis E virus (HEV) is the major etiologic agent of enteric hepatitis worldwide. It is primarily transmitted by fecal-oral transmission, although it can also be spread through person-to-person contact and blood transfusions.
HEV is a single-stranded, positive-sense RNA virus with a diameter of 27 to 34 nm and is a member of the family Hepeviridae. It has four genotypes that affect mammals.
The most common hosts of HEV are pigs, deer, rabbits, and humans. Other mammals, such as dogs and cats, may be at risk of infection.
Infection with HEV causes an acute illness that usually lasts a few weeks. In rare cases, hepatitis E can cause severe hepatitis and fulminant hepatitis that require hospitalization and treatment. It can be more severe in people with a suppressed immune system or in pregnant women. Pregnant women who become infected with hepatitis E are at increased risk of fetal loss, fulminant liver failure, and death.
Hepatitis is inflammation of the liver and can be caused by many different things, including viruses, other infections, alcohol, and drugs. It can be self-limiting or progress to fibrosis (scarring), cirrhosis, or cancer of the liver.
Viral infection is the most common cause of hepatitis.There are five hepatitis viruses, each of which causes a slightly different type of liver disease.
Viral hepatitis is an inflammation of the liver that usually happens as a result of infection with one of these five types of viruses, another virus, an autoimmune disease, or drugs that damage the liver. The most common symptoms include a poor appetite, nausea, vomiting, and fever.
The hepatitis F virus was first discovered in 1994 and is believed to be responsible for some cases of hepatitis that are transmitted through contaminated food or water. This virus was also found to cause post-transfusion hepatitis in some children who had undergone liver transplantation. The reason for this is unknown, but it may be related to the way that hepatitis F affects the blood clotting process.