Global tuberculosis levels plateau while extensively drug resistant strains increase

British Medical Journal | March 31, 2007

The World Health Organization has issued a report announcing that levels of global tuberculosis have reached a plateau, while at the same time warning that extensively drug resistant tuberculosis and the confluence of HIV and tuberculosis remain urgent public health concerns.

“There is both good news and bad news, and they are connected,” says Mario Raviglione, the director of WHO’s Stop TB campaign. “The positive is that the incidence, per capita, is declining. The disease may have reached its peak. But the bad news is that the decline is slow, too slow.”

WHO has been striving to meet two separate sets of goals with regard to tuberculosis. The first, set by the organisation’s governing body, the World Health Assembly, in 1991, was to detect 70% of cases by 2005 and cure 85% of those cases by the same year (the original target date of 2000 was postponed). The second is an aim of the United Nations millennium development goals of halving both the prevalence of tuberculosis and the mortality caused by the disease by 2015.

Although progress has been made, success in achieving these goals has been far from perfect. Global rates of tuberculosis detection reached 60% by 2005, and 84% of those cases were cured. “We’re informally describing this as a ‘near miss,’” says one WHO staffer who worked on the report.

The challenge posed by the millennium development goals is that the numbers were set in 1990, before two factors that sent tuberculosis rates skyrocketing throughout the decade—firstly, the spread of HIV in Africa, and, secondly, the break-up of the former Soviet Union, with the concurrent disintegration of health systems (which led to a doubling of the tuberculosis caseload during the ’90s).

So, as Chris Dye, WHO’s coordinator of tuberculosis monitoring and evaluation, explains, “We have to reverse what happened in the ’90s. Only then we can move on to trying to halve the 1990 rates.”

It will take three to four years to confirm whether the stabilisation in tuberculosis rates truly represents the beginning of a decline. Globally, 8.8 million tuberculosis cases are still being reported annually, with 1.6 million deaths per year. One third of the world’s population carries the tuberculosis bacteria.

New tools—diagnosis methods, vaccines, and treatments—are on WHO’s agenda, but a yawning funding gap exists. Marcos Espinal, executive secretary of the international Stop TB Partnership, notes that a $31bn (€23bn; £16bn) gap exists for the partnership’s 10 year plan to fight the disease. New diagnostics are in development and projected for use in 2008; similarly, a new vaccine is projected for 2014. The total cost of tuberculosis, divided among 84 countries, was $3.1bn for 2007.

Although extensively drug resistant tuberculosis is a relatively recent phenomenon and accounts for only a small percentage of tuberculosis cases, it is high priority for tuberculosis researchers. Defined in 2006 as resistance to both first and second line drugs, it exists in 35 countries, including all the G8 countries, the world’s major industrialised countries.