Hepatitis B is a virus that affects the liver. It is more prevalent in Asia and Africa and can be either acute (more common), resolving itself relatively quickly with no long term liver damage, or chronic (in about 20% of cases) lasting six months or more, and sometimes even for life with symptoms coming and going randomly.

Hepatitis B is normally transmitted via contact with infected bodily fluids or blood and only a very small amount of blood is required to transmit the disease because it is that infectious. In the developed world the virus is normally spread via sharing of contaminated needles, unprotected sex and the sharing such things as razor blades. In less developed countries where blood products are not screened properly or medical equipment is not sterilized adequately, this can also lead to the spread of the virus.

Hepatitis B viruses have an incubation period of between six weeks and six months, but approximately one third of all cases show no symptoms of the disease at all. In another third of cases, symptoms appear flu-like in nature and can include aches, pains and weakness; fever; headaches; loss of appetite; jaundice; diarrhea; and, vomiting and nausea. In the last third of cases, the virus can cause severe illness that can last for a long time (many months in some cases).

Vaccines are available nowadays against hepatitis B, but treatment for those infected normally includes nothing more than rest and recuperation. Drug treatments may be required for chronic types of the disease, to prevent damage to the liver and other parts of the body.