The study, the first in India to look at the prevalence of XDR-TB, found this type of TB accounts for 8% of multi-drug-resistant cases, compared with about 4% in the United States.

MDR-TB (multi-drug resistant TB) describes strains of tuberculosis that are resistant to at least the two first-line TB drugs, isoniazid and rifampicin. XDR-TB is MDR-TB that is also resistant to three or more of the six classes of second-line drugs. XDR-TB leaves patients (including many people living with HIV) virtually untreatable using currently available anti-TB drugs.

Recent findings from a survey conducted by the World Health Organization and the Centers for Disease Control and Prevention found that XDR-TB has been identified in all regions of the world but occurs most frequently in the countries of the former Soviet Union and in Asia.

Sushil Jain of the Hinduja National Hospital in Mumbai, India, and colleagues examined 3,904 lab samples at their hospital, and found that 1,274 were positive for Mycobacterium tuberculosis. Of these, 32% were found to be MDR-TB, out of which 8% were XDR-TB.

Tuberculosis can infect many sites in the body but most commonly affects the lungs. All XDR-TB cases were in patients with pulmonary tuberculosis, or TB found in the lungs, which can be spread by coughing, sneezing, laughing or singing. Repeated exposure to someone with TB disease is generally necessary for infection to take place.

The death rate of XDR-TB patients in the study was 42%, which Dr. Jain calls "alarmingly high."

"An important finding was that the majority of patients with XDR-TB were of younger age group (their average age was 30 years), thus posing a major threat to our economically productive population," Dr. Jain notes. "Serious efforts are needed to tackle this deadly disease which may become a global emergency." Dr. Jain says that XDR-TB has long existed in India but has been under-recognized and under-treated.

"Most labs in India are not equipped to perform drug susceptibility tests so exact prevalence is difficult to ascertain, and treatment in the absence of reliable sensitivity reports is difficult. Compounding the problem is the huge costs of treating these most difficult TB patients," he said.