Hepatitis, also known as viral or virus hepatitis, is defined as an acute inflammation of the liver caused by one of the hepatitis viruses: Viral hepatitis A (HAV, formerly known as infectious hepatitis); viral hepatitis B (HBV, formerly known as serum hepatitis); viral hepatitis non-A non-B (other viruses, including C), one of which is known as hepatitis C. Viral hepatitis is a leading cause of death and suffering. In the past years, new hepatitis viruses have been proposed. There are now effective (but expensive) vaccines to prevent hepatitis A and B, though none for hepatitis C and other more poorly known forms.
Although the forms of hepatitis differ etiologically and epidemiologically they are similar clinically. The characteristic symptoms and signs include anorexia, nausea, vomiting, abdominal distress, liver enlargement and jaundice. Unicteric cases (cases without jaundice) are common. The duration of illness is usually between two to eight weeks but may be longer. Attacks are more severe in the old than the young, in whom the disease may be mild and brief. Persistent or chronic active hepatitis may follow HBV or hepatitis non-A non-B, but not HAV. This occurs especially when infection is acquired in infancy and childhood.
Viral hepatitis A is usually spread by the intestinal-oral route; infection occurs readily in conditions of poor sanitation and overcrowding. A common source of epidemic outbreak is contaminated food and/or water. The incubation period varies from between 15 to 50 days. In countries with poor standards of hygiene and sanitation the majority of infections occur in children under the age of ten, often without any clinically apparent disease. In countries with high standards of hygiene and sanitation, only 10-15% of infections occur during childhood.
Viral hepatitis B is spread parenterally (not through the alimentary canal) with an incubation period of between 50 to 160 days. In areas of low endemicity the majority of cases occur in adults, whereas in hyperendemic areas the infection predominates in infancy and childhood. The HBV involves a long disease-causing process so of those infected in their teens, many would have a significantly shortened life.
Viral hepatitis non-A non-B can be diagnosed only when infection by viruses of hepatitis A and hepatitis B have been ruled out. The faecal-orally transmitted or water-borne form has a short incubation period and resembles HAV, whereas the blood-borne form, which has a long incubation period, resembles HVB. Delta hepatitis is an additional form of hepatitis caused by defective delta virus. This a unique agent capable of replication only in the presence of HVB.
Hepatitis non-B, a sometimes fatal virus that infects the liver, is now known as hepatitis C. Currently physicians are baffled by the virus' course of infection and the method by which to treat it. New studies have underlined the immune system's inability to combat the virus as it permanently affects the liver. Those infected with the virus will most likely become chronic carriers, whether or not they display symptoms of the disease. Currently antiviral drugs help clear the virus from carriers, but they are not as effective as required, particularly with middle-aged and older people.
Although hepatitis has been acknowledged in its basic form since ancient times, it became the subject of intense investigation during the 1940's when a mass of WWII soldiers fell victim to the virus' rage. British and American physicians, frustrated by the scourge and intent on discovering a cure, conducted experiments on children with Down's Syndrome and prisoners. These monstrous and highly unethical experiments led to the isolation of the hepatitis virus, the discovery of its transmission through the bloodstream, and the development of the hepatitis B vaccine.
There is speculation among physicians that hepatitis C is a more recent development in medical history, as it seems to have been a highly rare form of hepatitis in the 1940's. Some propose the virus spread significantly with the epidemic of intravenous drug use in the 1960's and 1970's.
Hepatitis A (HAV) has a worldwide distribution. There are at present at least 200 million persistent carriers worldwide. In Europe, about 50% of the cases are children under 15 years of age. The direct cost of hepatitis in countries surveyed by the World Health Organization is estimated at US$ 20,000 to $75,000 per 100,000 population. Two thirds of these costs can be attributed to hepatitis A.
Worldwide there are an estimated 300 million persons with ongoing hepatitis B infection and 60-100 million with chronic hepatitis C, conditions that may lead to liver failure or cancer. A significant percentage were infected in their early years of life – whether from birth or at a very young age – and are likely to die earlier or have a shortened life.
The potential severity of hepatitis A increases with the age of the infected individual. Most children experience symptomless infections and rarely develop jaundice. However, most infected adults develop the usual symptoms, including jaundice. About 0.3% of all reported cases are fatal. Risk of serious infection increases with age, especially for persons age 40 or older.
The case fatality rate of hepatitis is between 1 in 500 to 1 in 1000; exceptions are hepatitis B following blood transfusion and, in some countries, hepatitis during pregnancy.
Hepatitis is an occupational hazard among health care personnel and the staff of closed institutions. High rates of infection have been reported in drug abusers, prostitutes, and male homosexuals.