WASHINGTON-AIDS is the leading cause of death in Africa. In Harare, Zimbabwe, four out of 10 adults are HIV-positive. The full force of the epidemic has yet to hit, but it becomes clearer all the time that AIDS will have vast and long-term consequences for many societies. Fewer people in the West are dying of AIDS, thanks to new drug regimens, but even here the virus is not defeated. Last year in North America there were some 44,000 newly reported infections.

These are some of the gloomy tidings from Peter Piot, a Belgian physician and microbiologist who directs the U.N. program on AIDS. Last year, according to the World Health Organization, about 54 million people died. AIDS was responsible for 2.3 million of those deaths-more than malaria or tuberculosis or lung cancer.

AIDS is now among the top five killers in the world, and in many places the epidemic is still advancing. Its toll is especially high in developing countries, most of all in Africa, where the virus originated. In Botswana, children born in the next few years can expect to live, on average, to just past their 40th birthdays. Were it not for AIDS, their life expectancy would be 70. The picture of reduced life spans and orphaned children is repeated throughout much of southern and eastern Africa. Some 1.4 million Latin Americans, nearly a million North Americans and 7 million Asians also are living with HIV, and India and China may still lie ahead in the epidemic's path (The Washington Post, July 19, 1999).