Although it has been over five years since the initial reports of a virus related to KS were made, it is still unclear just how this virus is transmitted. Studies by various investigators have shown a clear and fairly striking relationship between the number of sexual partners that gay men have and positive blood tests for the virus. However, it is still unclear what activities increase the risk of spreading the infection. Martin et al., at the University of California, San Francisco, looked at the chance of detection of HHV-8 in various body fluid samples. They found that HIV-positive subjects had much higher levels of HHV-8 in bodily tissues than HIV-negative patients. The highest concentrations were in blood and saliva with 48% and 35% of these samples being positive for HHV-8. Substantially less was seen in semen; only 15% of the samples were positive. No samples of stool were positive for the virus. Based on this information, it might seem likely that oral genital sexual contact may be the most risky act for the transmission of HHV-8. However, other studies have shown conflicting results as to which sexual act might be most risky. Therefore, the authors could not recommend avoiding any single or specific group of sexual activities that might lead to a high likelihood of transmission.
Lawrence Corey at the University of Washington performed similar studies and had similar findings, including a 50% rate of shedding of virus in the saliva or throat compared to an 8% rate in the genital or anal region. He noted that the titer of HHV-8 in the mouth was approximately 2-1/2 times higher than any other mucus membrane. He asked why there is so little HHV-8 seropositivity in the HIV-negative population when saliva appears to be an infectious fluid that is transmitted between many people in most parts of the world. He also spoke of data from his laboratory suggesting that cytomegalovirus may act as a cofactor and increase the shedding of HHV-8, besides causing many life-threatening infections in HIV patients.
Studies of HHV-8 transmission within relatively isolated populations, one in French Guiana and one in Cameroon, revealed an even more confusing pattern of transmission. These groups were studied for HHV-8 positivity and transmission. It was found that there was a high correlation between seropositivity between mother and her children, as well as between siblings; there was no relationship between the likelihood of infection between spouses. Also, in Cameroon specifically, most people that develop evidence of an HHV-8 infection will do so before the age of 20. This is before the time of peak sexual transmission in this population. This suggests that the main routes of HHV-8 transmission in non-homosexual populations are from mother to child and between siblings. No good theory was proposed as to why this might be true, and further work needs to be done to answer these questions.