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The number of new tuberculosis (TB) infections each year is increasing, according to a study by the World Health Organization (WHO) published yesterday (8 June).

The study's authors say that although efforts to detect and treat TB are making headway — particularly in Asia — the situation in Africa is less promising.

But overall, add the authors, the UN target of halving the number of people affected by the disease by 2015 can still be met.

"Undoubtedly many more patients are getting treatment and many more lives are being saved," said lead author Christopher Dye, of the WHO's Stop TB department, at a press conference on 7 June.

"I am rather optimistic about what we can do [to achieve the UN goals] in Asian countries," added Dye. "I am somewhat less optimistic about what we are seeing in Africa."

Dye and colleagues evaluated the number of TB infections worldwide, and related their findings to internationally agreed goals of slowing the spread of the disease.

They published their findings in a special issue of JAMA (the Journal of the American Medical Association) focusing on tuberculosis.

In 1991, the WHO set targets for TB control, to be reached by 2000: to detect 70 per cent of new cases each year, and to successfully treat 85 per cent of these. But the targets were missed and so deferred to 2005.

In 2000, the UN adopted the Millennium Development Goals, a set of targets to be achieved by 2015. These included halving the number of people suffering from and being killed by TB.

According to Dye and colleagues, only 45 per cent of the new TB infections worldwide in 2003 had been detected. They estimate that for 2005 this figure will be 60 per cent — still short of the WHO's target of 70 per cent.

"The recent acceleration has been mostly due to rapid implementation [of WHO-approved methods] in India, where case detection increased from 1.7 per cent in 1998 to 47 per cent in 2003, and in China where case detection increased from 30 per cent in 2002 to 43 per cent in 2003," write the authors.

Also in 2003, 82 per cent of TB patients were treated successfully. This is close to the WHO's 2005 target of 85 per cent. However, the authors point out that there are significant regional differences.

In China, for instance, 93 per cent of patients were successfully treated, whereas in African nations, the figure is 71–74 per cent.

Globally, the number of new infections is slowly climbing (by one per cent each year). However, the authors say that reversing this trend is possible, particularly if TB transmission is reduced in countries where there are many cases of infection.

Reducing the number of people who die of the disease, however, will be more difficult. The varying success that different regions have had in treating the disease is key.

Africa and Eastern Europe are particularly problematic, because of the region's HIV/AIDS epidemics and emergence of TB bacteria that are resistant to drugs.

AIDS patients are particularly vulnerable to TB because their immune systems are weakened.

"Where there is HIV, there is likely to be TB, so let us actively go to those groups and search the people who have TB and give them treatment earlier," said Dye.

He added that African countries have a good record of introducing the 'DOTS' strategy, advocated by the WHO. DOTS is a public health strategy that describes how a country should fight the disease, including the best way of detecting and treating TB.

"African countries were the first to adopt DOTS and take it seriously," said Dye, pointing out that Tanzania was used by health policy experts as an example of how to implement the programme in a poor country.

"But since then, HIV has taken over," said Dye.

Dye said that Africa needed to start implementing DOTS across the continent to reduce its TB epidemic.

"There are few, if any, countries south of the Sahara where TB is in decline," said Dye. "It is more or less stable in West Africa which is less affected by HIV."

But elsewhere across Africa, TB is on the increase, he said. "It is just a matter of how quickly."

Unless DOTS is rigorously implemented, said Dye, "it will be difficult to add anything on top of it."

He cited distributing drugs to fight HIV as an example of a measure that could be implemented now and would help fight the spread of TB.

Dye said that over the next 10–15 years, we could expect to see new diagnostics, drugs and possibly even a vaccine added to the arsenal used to fight TB.

Reference: Journal of the American Medical Association 293, 2767 (2005)