MDR TB more frequent than thought in southern Africa

Re-analysis of multidrug-resistant tuberculosis (MDR-TB) reports using available data shows that ten out of 20 regions with the highest incidence of MDR-TB per 100,000 inhabitants are in southern Africa, and eight of ten are in South Africa.

The highest incidence was found in the Karakalpakistan district of Uzbekistan (35 cases per 100,000), with Kazakhstan ranked second (22 per 100,000), and four provinces of South Africa (Limpopo, North-West, Mpumalanga and KwaZulu-Natal) reported 1 – 15 cases per 100,000 notifications.

Dr Ruth McNerney of the London School of Hygiene and Tropical Medicine noted that although MDR-TB cases comprised a low proportion of total TB cases in the region, the population incidence was nevertheless higher than many parts of Eastern Europe and Asia traditionally seen as worst affected by MDR-TB.

The severity of a country’s multidrug-resistant TB problem can be expressed in a number of ways:

• The total number of cases (this shows up where the largest number of cases live, but will over-emphasise the largest countries, China and India).
• The proportion of new TB cases with MDR-TB (this shows where first-line TB control efforts may be weakest)
• MDR-TB incidence per 100,000 inhabitants (this method show where the proportion of people within the total population with MDR-TB is highest, and therefore where the risk of transmission is highest).

Using published data on MDR-TB incidence, Dr McNerney calculated that the five countries with the highest proportion of MDR-TB cases among their TB notifications were Israel, Kazakhstan, the Orel district in Russia, the Karakalpakistan district in Uzbekistan, and Estonia.

But when the incidence of MDR-TB per 100,000 inhabitants was calculated, it was revealed that southern Africa, and South Africa in particular, had the highest population incidence.

While Karakalpakistan in Uzbekistan had the highest incidence (35 per 100,000) and Kazakhstan was second (22 per 100,000), half of the 20 highest incidence countries were in southern Africa, with a population incidence between eight and 15 cases, and eight out of ten were in South Africa. The incidence was highest in KwaZulu-Natal, Mpumalanga, North West and Limpopo provinces.

The findings are likely to stimulate further demands for attention to MDR in southern African TB programmes, where, outside South Africa, MDR-TB has not been seen as a significant problem. The findings also highlight the seriousness of the MDR-TB risk in South Africa.