WHO warns about rising rates of drug-resistant TB

Feb 27, 2008 (CIDRAP News) – The World Health Organization (WHO), in a survey released yesterday, said the global number of multidrug-resistant tuberculosis (MDR TB) cases rose to a new high and is particularly worrisome in China and in former Soviet Union countries.

The 142-page report, available on the WHO's Web site, is the fourth global report on drug-resistant tuberculosis surveillance. The report includes data, collected between 2002 and 2006, from 90,000 patients with tuberculosis in 81 countries, according to a WHO press release yesterday.

For the first time the WHO's TB survey includes an analysis of extensively drug-resistant TB (XDR TB), revealing that 45 countries have recorded cases of the virtually untreatable disease. However, the WHO said in the press release that few countries have the equipment to diagnose XDR TB, so that number may not reflect the true global picture.

Some of the former Soviet Union countries reported some of the highest XDR TB rates, the WHO said. Of nine countries in that region that reported MDR TB data, about 10% of all MDR TB cases were XDR.

MDR TB is defined as TB that resists at least two key drugs that are considered first-line treatment for people who have TB infections—isoniazid and rifampicin, according to the CDC. XDR TB is described as a form of the disease that is resistant to the first-line TB drugs as well as the two most important second-line drugs (a fluoroquinolone and an injectable agent—amikacin, kanamycin, or capreomycin).

500,000 drug-resistant cases a year
Based on its survey findings, the WHO estimates that there are almost 500,000 new cases of MDR TB each year, which represent about 5% of the 9 million cases of all new TB types. The highest rate occurred in Baku, the capital of Azerbaijan, where 22.3% of all new TB cases were the MDR TB type, the WHO statement said. Other hot spots include Moldova (19.4%), Donetsk in the Ukraine (16%), Tomsk Oblast in the Russian Federation (15%), and Tashkent in Uzbekistan (14.8%).

Data from China also indicate that MDR TB is widespread, the WHO reported. The survey revealed that china has the world's highest burden of cases. According to the WHO's estimation, China had 130,548 new cases in 2006, more than 25% of the global burden.

The WHO's findings also pointed to a link between HIV infection and MDR TB. For example, data from Latvia and the Ukraine found twice the level of MDR TB in patients coinfected with TB and HIV, compared to patients without HIV.

Other evidence suggests that the association between HIV and MDR TB may be related to environmental factors, such as transmission in congregate settings, rather than biological factors. Though the association requires more study, infection control improvements in healthcare facilities and prisons, for example, may help address these coinfections, the WHO reported.

In the United States, the rates of MDR TB are rapidly decreasing, according to the WHO report.

The WHO pointed to some gaps in worldwide drug-resistant TB data. Only six countries in Africa were able to provide the drug resistance data, though the region has the world's highest incidence of TB. The problem is that many of the countries lack the equipment and personnel to identify drug-resistant TB, the WHO said.

Global assault needed
Mario Raviglione, director of the WHO's Stop TB department, said in the news release that urgent global efforts are needed to contain the spread of the disease. "TB drug resistance needs a frontal assault. If countries and the international community fail to address it aggressively now we will lose this battle," he said.

TB programs across the globe need to immediately improve their ability to rapidly diagnose all TB cases and treat patients until they are cured, Raviglione said, "which is the best way to prevent the development of drug resistance."

For example, 13 years after the Baltic countries of Estonia and Latvia were labeled drug-resistant TB hot spots, substantial investments and sustained efforts to control the disease have stabilized MDR TB rates and lowered TB case notifications, the WHO reported.

The WHO puts the price tag to control TB in low- to middle-income countries in 2008 at $4.8 billion, with $1 billion allocated toward MDR TB and XDR TB efforts. However, it said the world faces a $2.5 billion-funding gap, including $500,000 million for MDR TB and XDR TB.

See also:

Feb 26 WHO press release on drug-resistant TB report

CDC fact sheet on TB

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