The virus known as herpes virus 8, which was discovered six years ago, causes a skin cancer called Kaposi's sarcoma. Between 30 percent and 50 percent of HIV-infected people who catch herpes virus 8 will eventually get Kaposi's sarcoma.
Kaposi's sarcoma has been recognized for centuries in Southern Europe, the Middle East and Africa. But it was rare in the United States until the start of the AIDS epidemic in the early 1980s and occurs almost exclusively in people with AIDS.
Until now, it has been unclear how the virus spreads, although some suspected it is transmitted through sexual intercourse. However, new research from the University of Washington contradicts that idea.
Dr. John Pauk and others tested 39 gay men who were infected with the virus but did not have Kaposi's sarcoma. They found the virus in 30 percent of their saliva samples and mouth swabs, compared with 1 percent of anal and genital samples. When present, the virus levels were also much higher in saliva than in semen.
"The important thing is it suggests that oral-oral contact plays some role in transmission, although more study is needed to confirm that," said Pauk.
The study also found that those who engaged in "deep kissing" open-mouth kissing that involves a lot of contact with saliva appeared to be at substantially higher than usual risk of catching herpes virus 8.
Dr. Patrick S. Moore of Columbia University in New York, who discovered the virus, said exposure to saliva may explain the high rate of infection in parts of Africa, where more than 70 percent of people may carry herpes virus 8.
Kaposi's sarcoma causes purple skin blotches and can also attack the internal organs. Like many other diseases that kill people with AIDS, it usually gets established only in those who have weakened immune systems. The virus alone rarely causes sickness among people with normal disease defenses.
The new research "definitely has public health implications for people infected with HIV," said Dr. Ronald O. Valdiserri of the U.S. Centers for Disease Control and Prevention.
However, "at this point, the exact prevention messages are uncertain," he said, since there is not enough data yet to recommend that people with HIV avoid deep kissing.
Experts say that in the United States the virus is still largely confined to homosexuals, and this is why kissing has not yet spread herpes virus 8 among heterosexuals.
Dr. Anna Wald, another University of Washington researcher, noted that herpes virus 8 is closely related to the common Epstein Barr virus, which causes mononucleosis, long known as the kissing disease.
"Teen-agers tend to get this when they start kissing," she said. "The reason they get Epstein Bar virus and not herpes virus 8 is that most people have Epstein Bar virus, but relatively few have herps virus 8."
Other forms of the herpes virus cause chicken pox, shingles, cold sores and genital herpes.
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