India has become an incubator for a dangerous, drug-resistant strain of tuberculosis that is raising alarms about a global public health emergency, The Wall Street Journal reports.

Despite years of medical warnings about drug-resistant TB, doctors in India are reportedly seeing a growing number of patients with the disease who do not respond to any treatments.

"We finally have ended up with a virtually untreatable strain" of TB in India, said Dr. Zarir Udwadia, one of the country's leading TB authorities, in an interview with the paper.

In December, Udwadia reported in a medical journal that he had four TB patients resistant to all treatment. By January, he had 15.

Health-ministry officials denied the reports and accused Udwadia and his colleagues of starting a panic. But a Mumbai official seized patient samples for verification in government labs.

In April, the government confirmed the strain, according to internal Indian health-ministry documents reviewed by The Wall Street Journal.

Dr. Mario Raviglione, director of the Stop TB Department of the World Health Organization, said the global health agency is assisting India to combat the strain. Officials are concerned its spread could once again make TB the fatal plague that killed two-thirds of people afflicted before treatments were developed in the 1940s.

The number of known cases in India is small. Udwadia's patients are in Mumbai, at the P.D. Hinduja National Hospital & Medical Research Center. In Bangalore, St. John's National Academy of Health Sciences has seen six cases. And in New Delhi, the All India Institute of Medical Sciences has confirmed another two, said officials at the institutions.

"While this handful of cases is worrying, it's just the tip of the iceberg," said Dr. Soumya Swaminathan, of India's National Institute for Research in Tuberculosis. For treatments, Udwadia said, "We've got nothing."

Ashok Kumar, head of India's tuberculosis-control program, told the Journal the government was "seriously addressing" the widening drug-resistance problem. But he refuted Udwadia's description of a "totally drug-resistant" TB strain — not because there is a treatment, but because the term isn't internationally recognized and a new cure could be discovered.

Public concern about drug-resistant TB, he said, "is not a well-founded fear," he said, adding that Udwadia should have reported the cases to local health authorities, instead of al medical journal.

TB is a communicable, airborne disease that usually attacks the lungs and often strikes people living in poverty. Healthy, well-fed people are less likely to contract the disease when exposed.

India has the largest number of the world's cases — 2.3 million of the nearly nine million people afflicted annually. About 100,000 of India's patients are estimated to have drug-resistant strains.

For years, India was praised for having an ambitious TB treatment program, with 640,000 people who dispense medicines and 13,000 centers for diagnosis, the Wall Street Journal noted.

But the program is strained, with many patients treated by village nurses, who also supervise other health programs, said Swaminathan.

The government has promised to expand its treatment system by 2017, with the goal of quickly diagnosing and treating drug-resistant TB cases. But some experts doubt India can keep its promise, given the high cost of diagnostic equipment and the drugs needed to battle resistant strains.

World Health Organization experts met in Geneva to discuss untreatable TB in March, according to documents reviewed by the Journal. They decided against creating a "totally drug-resistant" category because the condition was difficult to confirm in a lab.

The Indian cases are the latest and most serious in a steady increase in resistance to tuberculosis drugs around the world. The first reports of so-called totally drug resistant TB came from Italy in 2007. Two years later, researchers in Iran reported patients who failed to respond to any known TB drugs.

Many countries have reported multidrug-resistant TB, which the WHO defines as a strain resistant to the two most powerful drugs. A smaller group of patients have extensively resistant TB — a strain resistant to most of the 12 known treatments — with survival rates that vary according to the quality of medical care.

The New England Journal of Medicine this month published a study showing 10 percent of TB patients in China had multidrug-resistant strains.

For almost two decades, Udwadia and his colleagues have been diagnosing patients with resistant TB, warning the strains could spiral out of control.

In 2003, he published a paper in the New York Academy of Sciences reporting that multidrug-resistant TB was rampant among patients at his hospital.