Health-care officials are increasingly concerned about emerging new forms of drug-resistant TB. According to the WHO, outbreaks of drug-resistant tuberculosis are showing up all over the world and threaten to touch off a worldwide epidemic of virtually incurable tuberculosis.
Drug-resistant strains have appeared in New York City prisons, a hospital in Milan, Italy, and many places in between. "Everyone who breathes air, from Wall Street to the Great Wall of China, needs to worry about this risk," says Dr. Arata Kochi, director of the WHO Global TB program.
An October 1997 survey by the WHO, the U.S. Centers for Disease Control and Prevention and the International Union Against Tuberculosis and Lung Disease estimates that 50 million people are infected with a strain of TB that is drug-resistant. Many of those are said to carry multi-drug-resistant tuberculosis-incurable by two or more of the standard drugs. In underdeveloped countries, where the vast majority of multi-drug-resistant TB cases have occurred, it is usually fatal.
"The world is becoming smaller and the TB bugs are becoming stronger," Dr. Kochi says. "While international travel has increased dramatically, the world has been slow to realize the implications for public health. Only recently have wealthy governments begun to recognize that the poor TB treatment practices of other countries are a threat to their own citizens."
The WHO study identifies hot zones of untreatable tuberculosis that threaten a worldwide crisis. These zones are home to nearly 75 percent of the world's TB cases and include Russia, Bangladesh, Brazil, China, Ethiopia, India, Indonesia, Mexico, Pakistan, the Philippines, South Africa, Thailand and Zaire.
Many of the hot zones are regional centers for travel, immigration and international economic activity. WHO officials admit that little can be done to prevent people infected with drug-resistant TB from traveling and spreading the bacilli to other countries.
According to the WHO, one third of the world's nations have a strain of TB resistant to multiple drugs. Untreatable cases account for 2 to 14 percent of the world's total. That number is low, but the WHO said lethal tuberculosis could spread rapidly because only one in 10 patients gets medical care that could overcome drug resistance.
Drug-resistant strains of TB develop when patients do not complete the course of treatment, fail to take their medicine or don't use medication properly. Tuberculosis often can be cured with a combination of four drugs taken for six to nine months. But some patients may begin to feel better after just two to four weeks of treatment, so they stop their medication. But not enough of the medication has been taken to kill all the TB bacteria in the patient. The remaining bacteria survive and mutate, becoming a tenacious, more deadly form of the disease.
TB can be diagnosed in several ways. Chest X rays can reveal evidence of active tuberculosis pneumonia, or they may show scarring, suggesting contained inactive TB. Examination of sputum under the microscope can show the presence of tuberculosis bacteria. A sample of the sputum can also be grown in special incubators, and tuberculosis bacteria can subsequently be identified.
Several types of skin tests are used to screen for TB. Tuberculin skin tests include the Mantoux test, the Tine test and the PPD. In each of these tests, a small amount of dead tuberculosis bacteria is injected under the skin. If a person is not infected with TB, no reaction at the site of the injection will become apparent. However, if a person has become infected with tuberculosis, an area around the site of the test injection will redden and swell. This reaction occurs 48 to 72 hours after the injection.
Drug-resistant strains have appeared in New York City prisons, a hospital in Milan, Italy, and many places in between. "Everyone who breathes air, from Wall Street to the Great Wall of China, needs to worry about this risk," says Dr. Arata Kochi, director of the WHO Global TB program.
An October 1997 survey by the WHO, the U.S. Centers for Disease Control and Prevention and the International Union Against Tuberculosis and Lung Disease estimates that 50 million people are infected with a strain of TB that is drug-resistant. Many of those are said to carry multi-drug-resistant tuberculosis-incurable by two or more of the standard drugs. In underdeveloped countries, where the vast majority of multi-drug-resistant TB cases have occurred, it is usually fatal.
"The world is becoming smaller and the TB bugs are becoming stronger," Dr. Kochi says. "While international travel has increased dramatically, the world has been slow to realize the implications for public health. Only recently have wealthy governments begun to recognize that the poor TB treatment practices of other countries are a threat to their own citizens."
The WHO study identifies hot zones of untreatable tuberculosis that threaten a worldwide crisis. These zones are home to nearly 75 percent of the world's TB cases and include Russia, Bangladesh, Brazil, China, Ethiopia, India, Indonesia, Mexico, Pakistan, the Philippines, South Africa, Thailand and Zaire.
Many of the hot zones are regional centers for travel, immigration and international economic activity. WHO officials admit that little can be done to prevent people infected with drug-resistant TB from traveling and spreading the bacilli to other countries.
According to the WHO, one third of the world's nations have a strain of TB resistant to multiple drugs. Untreatable cases account for 2 to 14 percent of the world's total. That number is low, but the WHO said lethal tuberculosis could spread rapidly because only one in 10 patients gets medical care that could overcome drug resistance.
Drug-resistant strains of TB develop when patients do not complete the course of treatment, fail to take their medicine or don't use medication properly. Tuberculosis often can be cured with a combination of four drugs taken for six to nine months. But some patients may begin to feel better after just two to four weeks of treatment, so they stop their medication. But not enough of the medication has been taken to kill all the TB bacteria in the patient. The remaining bacteria survive and mutate, becoming a tenacious, more deadly form of the disease.
TB can be diagnosed in several ways. Chest X rays can reveal evidence of active tuberculosis pneumonia, or they may show scarring, suggesting contained inactive TB. Examination of sputum under the microscope can show the presence of tuberculosis bacteria. A sample of the sputum can also be grown in special incubators, and tuberculosis bacteria can subsequently be identified.
Several types of skin tests are used to screen for TB. Tuberculin skin tests include the Mantoux test, the Tine test and the PPD. In each of these tests, a small amount of dead tuberculosis bacteria is injected under the skin. If a person is not infected with TB, no reaction at the site of the injection will become apparent. However, if a person has become infected with tuberculosis, an area around the site of the test injection will redden and swell. This reaction occurs 48 to 72 hours after the injection.
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