Health authorities in a remote Chinese region bordering one of Asia's major poppy fields have launched blanket surveillance tactics in medical institutions to account for every one living with HIV/AIDS in the region, local officials said Thursday.

The health bureau of Xinjiang Uygur Autonomous Region said hospitals and clinics should conduct mandatory AIDS tests for in-patients and 80 percent of the out-patients in counties, cities or districts, which reported 500 or more cases of HIV/AIDS each.

For cities or counties where more than 300 HIV/AIDS cases have been reported, hospitals are required to administer mandatory AIDS tests to all in-patients and at least half of the out-patients, authorities said.

Statistics from the regional health bureau show that by the end of last year, Xinjiang had reported 33,149 cases of HIV infection, about one tenth of the nation's total, ranking the fifth in China by the number of people being infected by the AIDS epidemic.

"The epidemic has shown a new trend," said Yin Yulin, Xinjiang's top health official. "While the spread of the virus among intravenous drug users remains hard to rein in, sex has replaced drug-taking as the main channel of Xinjiang's AIDS prevalence."

Yin said the epidemic has entered a stage of "high prevalence" in some parts of Xinjiang and it is "very difficult" to account for and monitor the movements of those testing positive for HIV or AIDS.

For decades, Xinjiang has been plagued by serious drug problems. The region lies on a trade route for illicit drugs that begins in the rich poppy fields of the so-called "Golden Crescent" area of Pakistan and Afghanistan. The prevalence of needle-sharing among drug users was previously blamed for the spike in Xinjiang's HIV/AIDS cases.

China has roughly 740,000 people living with HIV/AIDS. Nearly 80 percent of the HIV cases were reported in six provinces and regions, half of which lie on the country's western borders.