A virulent strain of tuberculosis resistant to most available drugs is surfacing around the globe, raising fears of a pandemic that could devastate efforts to contain TB and prove deadly to people with immune-deficiency diseases such as HIV-AIDS.

Known formally as extensively drug-resistant TB, or XDR-TB, the strain has been detected in 37 countries. It arises when the bacterium that causes TB mutates because antibiotics used to combat it are carelessly administered by poorly trained doctors or patients don't take their full course of medication. Rather than being killed by the drugs, the microbe builds up resistance to them.

At least 50 percent of those who contract this strain of TB will die of it, according to medical experts. In trying to stop the spread of the disease, which can be transmitted through coughing, spitting or even speaking, health officials have imposed sometimes extreme controls on infected people.

Robert Daniels, a 27-year-old dual Russian-U.S. citizen, underwent months of treatment for TB in Russia, where he often led a homeless existence. After telling people he was feeling better, he flew from Moscow to New York on Jan. 14 last year, then on to Phoenix.

In fact, his disease had not disappeared. The microbe causing it had mutated, apparently helped by his failure to complete a drug regimen in Russia. Weeks after arriving in Phoenix, Daniels was again coughing, feeling weak and losing weight.

Doctors in Phoenix diagnosed his illness as the new resistant strain of TB. Daniels again failed to follow doctors' orders, authorities say. So health officials got a court order, and he was locked up in the prison wing of a Phoenix hospital, where he has spent the past nine months in hermetically sealed isolation.

"It's not right," Daniels said in a telephone interview. "I'm not a criminal."

Daniels has become a case study in the bleak choices society faces in dealing with the new strain and attempting to balance protection of individual rights with protection of the public.

Evidence of TB has been found in ancient skeletons and mummified remains. From the 17th century to the 20th, it was a major killer in the United States and Europe, taking the lives of such notable people as the poet John Keats, the composer Frédéric Chopin, the writer Stephen Crane and the actress Vivien Leigh.

Even in the antibiotics age, TB has remained a scourge in poorer countries and communities. Today, one in three people globally is estimated to be infected with dormant TB, according to the World Health Organization (WHO). Most will never get sick, but in one in 10 cases the bacterium becomes active when the host's immune system is compromised. Worldwide, an estimated 1.7 million people die every year of the disease.

Two events last year alerted the medical community to a frightening new version of the disease. The Centers for Disease Control and Prevention, drawing on a survey of TB labs on six continents, reported that the prevalence of the super strain of TB increased from 3 percent of patients to 11 percent between 2000 and 2004. It reached 15 percent in South Korea and 19 percent in Latvia. There are no statistics yet about the new strain in Russia, China or Africa, areas with major TB populations .

In the United States, 13,767 TB cases were recorded in 2006, the lowest rate of infection since reporting began in 1953. A retrospective analysis by the CDC found 49 cases of the new strain in the country since 1993.

The CDC survey was followed by a report from Yale University researchers that the superbug had raged through a rural hospital in South Africa in 2005 and early 2006, killing 52 of 53 who contracted it, including six health care workers. The victims, apparently infected by airborne transmission of the virus, died on average just 16 days after diagnosis; most of them also had HIV.

"We have to come to grips with this quickly," said Vladislav Yerokhin, director of the Central Tuberculosis Research Institute in Moscow. "This is not just a threat for TB patients. This is a serious threat for the general population."

Russia has become a petri dish for drug resistance.

After the fall of the Soviet Union in 1991, rising poverty and a disintegrating medical system unleashed a TB epidemic in Russia and other post-communist countries. In 2005, the number of newly diagnosed cases in Russia reached 119,226, and 32,148 people died of the disease, according to the Ministry of Health and Social Development.

Up to 70 percent of TB patients in Russia are homeless, unemployed, in prison, former prisoners or alcohol abusers; 30 percent or more of patients break off their treatment, boosting resistance to anti-TB drugs.

In addition, Russia has an estimated 1 million people who are HIV-positive. That is an explosive combination, according to Murray Feshbach, an expert on Russian demography at the Woodrow Wilson International Center for Scholars in Washington. "It's potentially catastrophic for Russia," he said.

Today, South Africa is also a major TB infection zone. "The pressure of TB is enormous in our setting, and the majority of AIDS-related deaths are due to TB," said Gilles van Cutsem, medical coordinator with Doctors Without Borders in Khayelitsha, a large township on the edge of Cape Town, South Africa.

"People are wary about transmission within the community, as well as within health structures, from patients to patients and from patients to staff," van Cutsem said. "Considering that a great proportion of the health staff is also HIV-positive, this is even more of a concern."

Active TB bacteria are treated with four standard drugs. In most cases, patients quickly become non-infectious and start to feel better, although they are considered cured only after a full course of treatment, lasting about six months.

By the 1980s, doctors had begun to notice that some patients were resistant to these first-line drugs, particularly the two most potent ones, isoniazid and rifampicin. Their condition was defined as multidrug-resistant TB.

When the first line of drugs fail, doctors fall back on more expensive ones that have toxic side effects but can cure the condition after being used for 18 to 24 months. However, it is extremely difficult to keep patients taking the drugs for such a long period.

The new strain, a step up in resistance from the multidrug-resistant variety, has appeared more recently. An estimated 22,000 Russians have TB that is resistant to drug therapy to some degree. An unknown number of them have the new super strain.

If it is not contained, it will almost certainly mutate again into a completely drug-resistant TB, according to Mario Raviglione, director of WHO's Stop TB Department.

Some experts believe that may have already happened. Doctors reported this year that a 49-year-old woman in Italy died after 625 days of hospital treatment; all the drugs they tried failed.

The world is facing a return to the era before antibiotics when the white plague, as TB was known, was often a death sentence, according to Raviglione. The only treatment option then involved risky surgery in which doctors collapsed or removed an infected lung or attempted to cut out diseased tissue.

"We will be left with surgery and prayers," Raviglione said. "It's a desperate situation."

New drugs are in the pipeline but still years away, and patient non-cooperation could quickly undermine their effectiveness. "Monitoring patients is not easy when you are talking about a man who drinks a half a liter of vodka a day, or has no home or no family or no job, or all of the above. Those are our TB patients, " said Sergei Borisov, deputy director of the Phthisio-Pulmonary Institute in Moscow.

Some doctors and medical ethicists have said that countries will have to consider forced isolation of uncooperative patients, a public health strategy that evokes the sanitariums of decades ago.

"We have to face the possibility that restrictive measures may be necessary to control what could become a global pandemic," said Ross Upshur, director of the Joint Center for Bioethics at the University of Toronto. "I'm not advocating detention as a first resort," he added. "But if voluntary measures fail, people do not have the right to infect others. At the same time, people should be treated humanely, and they should have access to counsel, and they shouldn't be placed in a prison setting."

Other experts say such an approach might merely drive the disease underground and is impractical in poor countries.

"Forcing one uncooperative patient into isolation is fine, or even 10 patients or 100 patients," Borisov said. "But what about our situation in Russia, where 25 percent of the patients are uncooperative? Are we going to lock up thousands of patients? And where will we put them? Doctors cannot be prison guards."

Daniels, for instance, was often homeless when he was in Russia, according to him and his wife, Alla Danielova, an English teacher. Daniels said he bounced among friends' houses, partying and trying to ignore the bloody sputum he was coughing up. "I knew I was going to have to treat it, but I had other plans at that time," he said. "I didn't think it was a big deal. Now I know better."

Daniels acknowledged that he had visited a fast-food restaurant and stores in Phoenix without a mask but denied that he had stopped taking his medicine there. "That's a nasty lie," he said.

He said his condition is now improving. He has petitioned the court to be moved out of the prison ward and, ultimately, released. But last week a judge rejected his plea and ordered him to remain in medical confinement.