The greatest danger from virulent, drug-resistant strains of tuberculosis that worry the World Health Organization is in Asia, parts of Africa and in Russia (especially its prison system), according to Hebrew University of Jerusalem tuberculosis expert Prof. Hillel Bercovier. The danger in Israel from these newly identified strains, called XDR-TB, is low because "of the sun, the way we live and the epidemiology here," he told The Jerusalem Post Wednesday. "But the Health Ministry still has to be careful and monitor patients for these strains." Half of all HIV/AIDS patients also have tuberculosis because of their weakened immune system, and immigrants from certain parts of Africa arrive as HIV carriers, Bercovier said. The XDR-TB strains have not been isolated yet in Israel, he added. The Health Ministry did not comment by press time. Antibiotic-resistant strains are less likely to appear where tuberculosis patients get directly observed therapy - a cocktail of antibiotics taken on schedule for months. If they stop taking the pills when they feel better, the tubercle bacillus (the bacterium that is a major cause of tuberculosis) can develop resistance. All Israeli tuberculosis patients get directly observed therapy, so resistance is not a major problem here. It is a significant danger in countries in the developing world where tuberculosis treatment is non-existent or non-supervised, said Bercovier, who is also the university's vice president for research and development.