A NEW United Nations report draws a stark picture of the AIDS virus devastating the dimly aware populations of several African countries. The worst-hit are Zimbabwe and Botswana, where one in four adults is infected with HIV. That forecasts an awesome body count from AIDS-related illnesses in the next decade.

Africa has 21 million of the world's 30 million HIV-infected people.

The epidemic is believed to have started in Africa, so it has had longer to get established on that continent. It is spread there mainly by heterosexual contact - women get it as frequently as men. The prevalence of other sexually transmitted diseases makes it easier for HIV to spread through open sores. Pregnant women and nursing mothers pass the virus to their children.

Ninety percent of the HIV carriers in Africa don't know they are infected. They are not tested and have no access to treatment anyway. And many African governments foolishly refuse to undertake prevention campaigns that would slow the spread of the virus.

Several factors contribute to sub-Saharan Africa's standing as the most severely affected area, where infection rates dwarf those in wealthy nations. The 10 percent-plus HIV infection rate in 13 African countries compares with a worldwide rate of 1 percent, and three-quarters of 1 percent in the United States where AIDS is a highly publicized public health threat.

An ironic tragedy is that millions of Africans could be spared infection with HIV, and eventual death from AIDS, if they were educated about how to minimize the danger (mainly by avoiding unsafe sex). A few countries that have launched prevention campaigns (Uganda is one) have been rewarded with sharp reductions in HIV infection rates. The U.N., having produced the horrifying statistics, should be the vehicle for dragging reluctant member nations into sensible prevention programs before another generation of Africans faces predictable disaster.