Hepatitis

I

Introduction

Hepatitis, inflammation of the liver, usually due to acute viral infection. It occurs in several forms. Lifelong immunity to the causative virus usually follows an attack, but since several distinct viruses cause the disease—at least five are now known—immunity to one type does not confer immunity to the others.

II

Hepatitis A

Previously known as infectious hepatitis, hepatitis A is caused mainly by poor sanitation and lack of hygiene. It is transmitted by food or water contaminated by excreta; by other objects taken into the mouth; from person to person, including by sexual contact; or by injection with improperly sterilized hypodermic needles or needles shared by intravenous (IV) drug users. Outbreaks often occur in army or refugee camps and in institutions where small children are crowded together. Shellfish and uncooked food carry risk of infection. This form of the disease has become more common as a result of increased travel to countries where hepatitis A is common and where clean water and proper sewage disposal are not available. Hepatitis A is usually less severe than hepatitis B and patients generally recover within weeks, whereas hepatitis B can last for months.

III

Hepatitis B

Previously called serum hepatitis, hepatitis B can be transmitted by intimate sexual contact, as well as from a mother to a foetus or newborn baby. Hepatitis B is also transmitted by injections transporting a virus-bearing serum, most often during blood transfusion, by contaminated needles and syringes used medically or for injecting drugs, and by acupuncture or tattooing. The virus is also present in other body fluids, such as semen, vaginal fluid, saliva, and tears.

Hepatitis B can cause lifelong infection and lead to cirrhosis (scarring) of the liver, liver cancer, and liver failure. It causes more than 250,000 deaths each year worldwide with the highest incidence in Africa, south-eastern Asia, Alaska, China, and the Amazon. In 2000 there were 565 cases reported in the United Kingdom which, compared with the 1984 figure of 3,000, represents a decline—although many cases go unreported.

In 1965 Baruch Samuel Blumberg, an American research scientist, identified a viral component (known as the Australia antigen) that determines whether a sample of blood can transmit hepatitis B. All samples of blood intended for transfusion are now routinely tested for the antigen; this has greatly reduced the incidence of post-transfusion hepatitis.

In 1977 an Italian doctor, Mario Rizzetto, identified a virus—now called the delta hepatitis virus—that cannot replicate on its own and requires the presence of the hepatitis-B virus to be transmitted. The delta virus occurs worldwide and has caused major epidemics; this form of the disease, sometimes called hepatitis D, can also become chronic and lead to liver failure.

IV

Hepatitis C, E, and G

Three more types of hepatitis have also been identified. Also known as non-A, non-B hepatitis, hepatitis C is mainly transmitted by infected blood and blood products, by contaminated syringes, or less commonly, in body fluids through sexual contact. It is caused by a virus that has now been cloned, and is the most common cause of post-transfusion hepatitis. About half of hepatitis C sufferers may suffer persistent infection. There is no vaccine available.

Hepatitis E is, like hepatitis A, transmitted in contaminated drinking water and can cause an epidemic form of the disease in tropical areas. There is no vaccine available. Hepatitis G virus is blood-borne; groups at risk include IV drug users and those who have been infected frequently with hepatitis C virus.