Scientists in Hong Kong and on the mainland are working on an AIDS vaccine to protect against three variants of HIV sweeping across southern and western areas of the mainland, Hong Kong and Taiwan.

Chen Zhiwei, director of the new AIDS Institute in Hong Kong, said scientists have been using gene sequencing to track how HIV viruses on the mainland are evolving, and their geographical spread.

Two closely related HIV variants had been spread by intravenous drug users (IDUs) from southwestern Yunnan Province; one to as far as Xinjiang in the northwest, and the second to Guangdong in the south.

The third variant is in Yunnan and southern Guangxi province, which Chen said is passed mainly through heterosexual sex.

Chen, who worked alongside the well-known HIV/AIDS scientist David Ho in the United States before moving to the Hong Kong institute, said scientists in the US and China have developed a vaccine based on the two HIV variants spreading among IDUs, which they hope to test on animals by the end of the year.

"If you want to make a vaccine, it is better to have a local strain as a target to work on," Chen said.

The HIV variants circulating in south and west China are similar to those found in India, Myanmar, Vietnam, Cambodia and Thailand, as well as in Taiwan and Hong Kong, he said.

"The epidemic in China has evolved over time. Previously, the major risk factors were IDUs and the tragic story of blood donation in central China.

"But after these people got infected, they passed it on and it is now in the general population," Chen said.

"After 2006, heterosexual sex has been playing the major role in transmission of the virus. Infections have gone up in the general population and from mother to child."

The presence of these variants in Taiwan and Hong Kong also could be a telltale sign of the traveling routes of drug users in the region, Chen said.

The AIDS Institute hopes to help set up HIV screening centers in China, which is estimated to have about 700,000 people living with HIV/AIDS.

Editor: Yan