RUILI, China -- Heavily mountainous, cloaked in tropical foliage, thinly patrolled and all but ignored by many neighboring villagers, the more than 1,200 miles of border between Myanmar (formerly called Burma) and China's southwestern Yunnan province is as porous as a sieve.
Just in the vicinity of this booming ruralcenter, more than 10,000 travelers a day use eight ferries and a small bridge to legally cross the Ruili River between the two countries, their cargo subjected to a minimum of official scrutiny. Under the cover of night, hundreds of others are believed to make the same trip illegally.
As a result of the thriving cross-border traffic, Ruili's raucous, half-mile-long central street market overflows with all manner of Southeast Asian goods for sale, everything from Thai powdered milk and medicine to locally produced teak and rubies.
Increasingly, however, another product of the "Golden Triangle" of Myanmar, Thailand and Laos is also turning up in this part of China: opium and heroin, drugs that are grown and processed in areas of Myanmar controlled by independent warlords and that are mainly bound for lucrative European and North American markets, particularly the East Coast of the United States.
A pronounced shift over the last few years in the transit routes used by the Hong Kong-based triad gangs that control the heroin traffic has meant that as much as 20 percent to 30 percent of Myanmar's total heroin production is now believed to be moving to the West through southern China, instead of through Thailand.
As a byproduct of this clandestine move ment of thousands of pounds of heroin through its territory, China for the first time in four decades is facing a rapidly growing drug addiction problem -- as well as an alarming increase in carriers of the AIDS virus, a development primarily linked to the injection of drugs with shared needles.
China has taken particular political pride in having virtually eliminated in the 1950s long-standing opium use by an estimated 20 million addicts. Now, however, officials admit to having at least 70,000 drug addicts, and the actual number could well be much larger.
The drug problem is heavily concentrated among the Dai and Jingpo ethnic minorities living in isolated border villages near Ruili. The area, called Dehong Prefecture, has an estimated 15,000 to 20,000 addicts among a total population of about 900,000, official reports say.
But heroin use already has spread from this remote area along transportation routes to Yunnan's capital city, Kunming, and to such far-flung Chinese cities as Chengdu, Lanzhou, Xian and Canton.
"We are facing a very serious situation," said Dr. Wan Wenping, a psychiatrist who heads the Kunming Drug Abuse Research Center. "The number of drug addicts is increasing at a very fast rate."
In certain villages near Ruili, virtually every man under the age of 30 is addicted, forcing women to do all the labor, according to a recent Chinese news report. In Kunming, an upswing in prostitution, robberies and street crime has followed in the wake of the drug epidemic. Throughout Yunnan, several hundred addicts have died from drug overdoses in recent years.
And as a result of the widespread sharing of needles by addicts, Yunnan, particularly Ruili, has become China's hot spot for the virus that leads to AIDS. Of 408 Chinese carriers of the fatal virus identified so far by China's limited blood-testing efforts, 397 of them are in Yunnan -- with 310 of them in the Ruili area.
Provincial health officials estimate that more extensive testing would reveal as many as 1,000 AIDS virus carriers in Yunnan, and they are now bracing for the spread of the disease by sexual contact -- particularly as most carriers are peasants with limited education. "Some don't fear AIDS because they think it's just a campaign by the government to terrorize them into stop using drugs," said Dr. Zhao Shangde, director of Yunnan's Anti-Epidemic Center.
In Chinese cities, opium and heroin initially regained favor in the late 1980s among "getihu," China's burgeoning class of street vendors and assorted small-scale private entrepreneurs, the first group with the money to indulge in the habit. In a country with an average monthly wage of less than $30, illegal drugs are not cheap: Yunnan addicts say a drug-laced cigarette costs at least $1; a gram of diluted heroin goes for $25.
But now addiction is cropping up among even Communist Party cadres and the military, said Dr. Li Jianhua, director of the Kunming Drug Treatment and Rehabilitation Center. More and more users have moved from smoking heroin to injecting it, Dr. Li said, and the average age of addicts is falling, with greater numbers of teen-agers and unemployed youth becoming addicted.
"People want to try drugs because they think it's a rich man's habit," explained Yang Qingming, 31, a patient at the Kunming treatment center, who lost his grocery store and barbershop to the habit.