The World Health Organization says Extensively Drug Resistant Tuberculosis ? also known as XDR-TB ? poses a grave public health threat. It?s why the head of the WHO?s Stop TB Department is in Washington to meet with US officials and members of Congress.

Dr. Paul Nunn says this new form of tuberculosis points out weaknesses in the health care systems in poor countries.

?The problem with drug resistant TB is that it?s an illustration of weaknesses in the underlying TB program. What it means is that we are probably not investing enough in TB control, particularly in the poorest countries of Africa. So that cases of tuberculosis are not being found - and when found, are not being properly supervised and treated. So that not enough of them are being cured and drug resistance is created,? he says.

The problem is made worse, he says, when TB occurs in areas where there?s a high prevalence rate of HIV, the AIDS virus.

He says, ?HIV allows outbreaks, small epidemics, of highly drug resistant disease to occur amongst groups of people who are HIV positive, with unfortunately an extremely high mortality rate.?

Southern Africa is seeing a growing number of cases of XDR-TB. Dr. Nunn says most of the countries there have now prepared plans for dealing with XDR-TB with help from the WHO. Rapid surveys are also underway in southern Africa to try to get better figures on the number of cases of the disease. However, in South Africa, the figures are more precise.

?From the 53 original cases in Tugela Ferry there are now thought to be about 170 cases in KwaZulu-Natal Province, and more than 400 cases in the whole country,? he says

Dr. Nunn is in Washington, DC, to discuss funding to contain XDR-TB. But with an unsettled US federal budget situation, it?s not clear how much the United States would or could commit. He has a preliminary estimate though of how much would be needed.

He says, ?Our baseline figure for addressing the XDR (TB) problem in Africa is around 300 million for the next year or so, 300 million US dollars. And this covers not only southern Africa, where we?ve already got a slightly more detailed costed plan, but the whole of the rest of Africa as well. Just over half of that really is required to reinforce basic TB control. But about a third is also required specifically to treat those patients who are known or suspected to have drug resistant disease. Up until now, most of Africa has not really addressed the drug resistance problem.?

The WHO official says the money, in part, would be used for staff and transportation to find and fully treat rural TB patients. This, he says, would help prevent those cases from transforming into Extremely Drug Resistant TB.