HEPATITIS A VIRUS
It is a very common disease evolving through small epidemics affecting young subjects. The contamination is oro-fecal. The disease does not confer cross-immunity with hepatitis B and does not progress to chronicity. The vaccine provides lasting immunity than 10 years.
HEPATITIS B VIRUS
It is a common disease in the world, particularly in Africa south of the Sahara and in Southeast Asia. The disease is mainly transmitted parenterally (syringes, needles, blood transfusions) and mainly affects hospital staff, hemodialysis patients, transfusion patients, and drug addicts. It can also be transmitted by saliva, sperm and thus through sexual contact. There is also the possibility of mother-to-child transmission. The disease does not confer cross-immunity with hepatitis A. It can progress to chronic hepatitis. Vaccination provides protection that lasts for several years. Its safety has been established in healthy subjects.
HEPATITIS C VIRUS
It is hepatitis that often evolves in the chronic mode. Incubation is 7 to 8 weeks. Transmission is mainly through blood: 90% of cases are due to transfusions, intravenous drug addiction, or hemodialysis. More rarely, the contamination can be done by sexual contact or perinatally in the newborn. Chronic hepatitis persists after the acute phase in 50% of cases, and 20% of these progress to cirrhosis, or even liver cancer in 2 to 6% of cases.
HEPATITIS D OR DELTA VIRUS
It can occur only in people with hepatitis B. Indeed, this virus needs the presence of the virus B to multiply. The infection may be simultaneous, or the virus D will infect hepatitis B. The mode of transmission is the same as for hepatitis B. The evolution of hepatitis B is often aggravated by the presence of this virus. In the serum anti-d antibodies are found.
THE HEPATITIS E VIRUS
This hepatitis is often benign except in pregnant women who may have fulminant hepatitis. The transmission is oral. Incubation is short for 15 to 50 days. Evolution is never towards chronicity. In the serum anti-HEV antibodies are found.
HEPATITIS G VIRUS
This virus was discovered in 1996 and would be transmitted mainly through the bloodstream. The main victims of this hepatitis are injection drug users. Still little known, this virus is often associated with that of hepatitis C. Its pathogenicity seems weak.