In the East African nation of Kenya, about 1 in 10 couples is affected by HIV

A 2007 study that tested the blood of a representative sample of 16,000 Kenyans between the ages of 15 and 64 found that only 15% of infected people knew they had the virus. The fraction of HIV-affected couples in which partners know each other's status is even lower - only 9%. In co-habiting couples, use of condoms, which could greatly lower the risk of transmitting the virus, is very low - about 5%. The consequence is that many of the continent's new infections occur among long-standing couples (albeit sometimes with the virus being introduced through an outside liaison). In Uganda, 65% of recent infections occur in married people. Furthermore, when one partner in an HIV-affected couple dies, that often opens new chances that the virus will be passed to others. In Zimbabwe, 8% - 17% of new HIV infections are attributed to the sexual activity of widows or widowers.