What Causes Kaposi Sarcoma?

Kaposi sarcoma (KS) is caused by infection with a virus called the Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV8). KSHV is in the same family as Epstein-Barr virus (EBV), the virus that causes infectious mononucleosis (mono) and is linked to several types of cancer.

In KS, the cells that line blood and lymphatic vessels (called endothelial cells) are infected with KSHV. The virus brings genes into the cells that can cause the cells to divide too much and to live longer than they should. These same genes may cause the endothelial cells to form new blood vessels and may also increase the production of certain chemicals that cause inflammation. These types of changes may eventually turn them into cancer cells.

KSHV infection is much more common than KS. Most people infected with this virus do not get KS and many will never show any symptoms. Infection with KSHV is needed to cause KS, but in most cases infection with KSHV alone does not lead to KS. Most people who develop KS have the KSHV and also have a weakened immune system, due to HIV infection, organ transplant, being older, or some other factor.

The number of people infected with KSHV varies in different places around the world. In the United States, studies have found that less than 10% of people are infected with KSHV. The infection is more common in people infected with HIV than in the general population in the United States. KSHV infection is also more common in men who have sex with men than in men who only have sex with women.

In some areas of Africa, up to 80% of the population shows signs of KSHV infection. In these areas the virus seems to spread from mother to child. KSHV is also found in saliva, semen, and vaginal fluid, which may be some ways it is passed to others.

For more on infections and their role in cancer, see Infections That Can Lead to Cancer.