Hepatitis means injury to the liver with inflammation of the liver cells. Toxins, certain drugs, some diseases, heavy alcohol use, bacterial and viral infections can all cause hepatitis.
Hepatitis is also the name of a family of viral infections that affect the liver; the most common types in the India and Asian countries are hepatitis A, hepatitis B and hepatitis C.
Types of Viral Hepatitis:
A group of viruses known as the hepatitis viruses cause most cases of liver damage worldwide. Common viruses cause hepatitis include A, B, C, D, E and G (95% cause of viral hepatitis). Other viruses include, Herpes simplex virus, Cytomegalovirus, Epstein-Barr virus, Yellow fever virus and Adenoviruses also cause hepatitis.
HCV infection in India has a population prevalence of around 1%, and occurs predominantly through blood transfusion and the use of unsterile glass syringes.
- Transfusion of infected blood and blood products,
- Unprotected sexual contact with an infected partner.
Most common cause of all viral hepatitis includes — •
• Use of infected needle and syringes,
• Intravenous drug users,
Hepatitis A virus: Infection causes due to eating raw shellfish from water polluted with sewage and contaminated food and water. Travel or work in regions with high rates of hepatitis A.
Carrier of Hepatitis B virus: Some people with Hepatitis B never fully recover from the infection (chronic infection), they still carry the virus and can infect others for the rest of their lives. HBV can be transmitted between family members within households by contact of non-intact skin or mucous membrane with secretions or saliva containing HBV.
Causes of Hepatitis C virus: Occurs as the result of percutaneous transmission of the hepatitis C virus through infectious blood. It can be passed from an infected mother to her baby. HCV can also be transmitted through household contact (sharing of personal items such as razors, toothbrushes, scissors and manicuring equipment within the same household).
Causes of Hepatitis D virus: HDV is transmitted parenterally, it can replicate independently within the hepatocyte, but it requires HBs Ag for propagation. Sexual transmission is less efficient than with HBV. Perinatal transmission is rare.
Causes of Hepatitis E virus: Infection spread by fecally contaminated water within endemic areas. On the other hand, in non-endemic areas, the major mode of the spread of HEV is food borne, especially undercooked pork.
Causes of Hepatitis G virus: It has been identified in all ethnicities, and 1% - 4% of worldwide blood donors are carriers of the virus at the time of blood donation.
Pathophysiology of Hepatitis
[I] Hepatitis A
Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus. The hepatitis A virus is one of several types of hepatitis viruses that cause inflammation that affects liver’s ability to perform normal function. Nearly everyone who develops Hepatitis A makes a full recovery; it does not lead to chronic disease. Mild cases of hepatitis A do not require treatment, and most people who are infected recover completely with no permanent liver damage.
After oral inoculation the virus is transported across the intestinal epithelium. After travelling through the mesenteric veins to the liver, the virus enters hepatocytes, where replication of hepatitis A virus (HAV) occurs exclusively within the cytoplasm via RNA-dependent polymerase.
The liver damage is due to direct killing of hepatocytes and by the host’s immune system response to infected hepatocytes indicates inflammation of liver. Microscopically there is spotty parenchymal cell degeneration, with necrosis of hepatocytes, with disruption of liver cell cords.
[II] Hepatitis B
Hepatitis B is a serious liver infection caused by the hepatitis B virus (HBV), which infects the liver and causes an inflammation called hepatitis, originally known as “serum hepatitis”. It ranges in severity from a mild illness, lasting a few weeks (acute), to a serious long-term (chronic) illness that can lead to liver cancer or cirrhosis (a condition that causes permanent scarring of the liver).
HBV infection in itself does not lead to the death of infected hepatocytes. The host’s immune response to viral antigens is thought to be the cause of the liver injury in HBV infection.
Liver damage arises from cytolytic effects of the immune system's cytotoxic T lymphocytes (CTL) which attempt to clear infection by killing infected cells. The cellular immune response, rather than the humoral immune response, seems to be primarily involved in disease pathogenesis. Induction of antigen-specific T-lymphocyte response is thought to occur when host T lymphocytes are presented with viral epitopes by antigen-presenting cells in lymphoid organs. These antigen-specific T cells mature, expand and then migrate to the liver. In acute HBV infection, most HBV DNA is cleared from hepatocytes through non-cytocidal effects of inflammatory byproducts of CD8+ T lymphocytes, stimulated by CD4+ T lymphocytes, notably interferon-gamma and tumour necrosis factor-alfa.
These cause down-regulation of viral replication, and trigger direct lysis of infected hepatocytes by HBV-specific CD8+ cytotoxic T cells. In contrast, people with chronic HBV infection display weak, infrequent, and narrowly focused HBV- specific T-cell responses, and the majority of mononuclear cells in livers of chronic HBV- infected people are non-antigen-specific.
[III] Hepatitis C
Hepatitis C is a liver disease caused by the hepatitis C virus (HCV). The virus can cause both acute and chronic hepatitis infection, ranging in severity from a mild illness lasting a few weeks to a serious, lifelong illness. Hepatitis C is usually spread through direct contact with the blood of infected person.
The natural targets of HCV are hepatocytes and possibly, B lymphocytes. Viral clearance is associated with the development and persistence of strong virus-specific responses by cytotoxic T lymphocytes and helper T cells. In most infected people, viremia persists and is accompanied by variable degrees of hepatic inflammation and fibrosis.
[V] Hepatitis E
It is a serious liver disease caused by the hepatitis E virus (HEV), usually results in an acute infection. It does not lead to a chronic infection.
Hepatitis E is an enterically transmitted infection typically self-limited. Hepatitis E has many similarities with hepatitis A. Hepatitis E has been associated with chronic hepatitis in solid organ transplant recipients, patients infected by HIV, and an individual on rituximab treatment for non-Hodgkin lymphoma.
Etiology and Pathophysiology
The hepatitis E virus (HEV) genome contains 3 open reading frames (ORFs). The largest, ORF-1, codes for the non-structural proteins responsible for viral replication. ORF-2 contains genes encoding the capsid. The function of ORF-3 is unknown, but the antibodies directed against ORF-3 epitopes have been identified.
HEV is an RNA virus of the genus Hepevirus. The virus is icosahedral and non- enveloped. It has a diameter of approximately 34 nanometres, and it contains a single strand of RNA approximately 7.5 kilobases in length. Four HEV genotypes have been identified. Genotypes 1 and 2 are considered human viruses; genotypes 3 and 4 are zoonotic and have been isolated from humans and animals.
[VI] Hepatitis G
A new virus recently identified in humans.
GB virus C (GBV-C), formerly known as hepatitis G virus (HGV) and also known as HPgV is a virus in the flaviviridae family and a member of the Pegivirus genus, is
known to infect humans, but is not known to cause human disease.
Hepatitis G virus and GB virus C (GBV-C) are RNA viruses that were independently identified in 1995, and were subsequently found to be two isolates of the same virus.
Common symptoms of all viral hepatitis includes —
• Nausea and vomiting
• Loss of appetite
• Weakness and fatigue
• Dark urine
• Pale stool
• Stomach pain and side pain.
• Abdominal pain