BANGKOK, Thailand (AP)-Two distinctly different forms of the AIDS virus are ravaging

Thailand-one passed primarily by needles and the other by sexual contact, researchers

say.

Scientists said they are at a loss to explain how two parallel AIDS epidemics could

occur in one country.

They suggested that one form of the virus may have evolved to spread readily through

drug infections, such as occurs when drug addicts share needles, while another might

more easily be passed during sexual intercourse.

Dr. Chin Yih Ou of the U. S. Centers for Disease Control, who directed the study,

said the "surprising" results may provide new clues for tracing the virus'

global spread, designing better drugs and creating effective vaccines.

The type spread sexually seems to have originated in Africa, while the variety among

drug-abusers seems to have come from the United States.

The study was initiated to hunt for clues about the staggering spread of AIDS in

Thailand, which has infected some 300,000 people. Currently more than a third of

the intravenous drug users in Thailand are infected.