Drug-resistant tuberculosis poses global risk, World Health Organization says
Saturday, March 20, 2010
The percentage of tuberculosis cases around the world resistant to two standard drugs remains low -- about 4 percent -- but is three to six times as high in the vast area that once encompassed the Soviet Union, according to a report released this week by the World Health Organization.
The report is based on information from 114 countries. Because testing for TB drug resistance is not uniformly carried out and is not even done in some countries, experts cannot say whether the problem is getting worse or better.
"What we can say is this is a serious threat to global health, with rich and poor countries, all countries, at risk," said Mario C. Raviglione, director of the WHO Stop TB Department.
In the Russian Arctic city of Murmansk, 28 percent of new TB cases in 2008 were "multidrug-resistant" (MDR) -- the highest fraction recorded in a region, the report said.
In the Central Asian nations of Kazakhstan and Tajikistan, the rates of MDR-TB were 25 and 17 percent, respectively. In Moldova and Belarus, in Eastern Europe, the rates were 25 and 17 percent. In the Baltic nations of Estonia and Latvia, they were 15 and 12 percent.
"We knew that it was serious, but we are reporting increasing levels that we thought were not possible before," Raviglione said. "We are in a situation that is out of control in some places."
Since 2000, no country outside Eastern Europe and Central Asia has reported rates of drug resistance higher than 6 percent. The much-higher rates there are attributed to several causes.
The collapse of the Soviet Union caused a decline in the quality of TB treatment, with many patients being treated with only one or two drugs, which promotes the emergence of resistant bacterial strains. Economic disruption led to more crowded living, which increases transmission. Populations in the former Soviet bloc also have high rates of alcoholism and smoking, which increase susceptibility to TB.
Despite the seriousness of the problem in Eastern Europe and Central Asia, nearly half of all MDR-TB cases occur in China and India. That's because those countries have so many TB cases overall. In its first nationwide survey in 2007, China found that 6 percent of new tuberculosis cases were drug resistant.
TB is a bacterial infection, usually affecting the lungs, although other organs can be involved. There were 9.4 million new cases in 2008. Treatment takes at least six months and requires that a person take four drugs at least part of the time. Worldwide, 86 percent of people with drug-susceptible TB were cured in 2007.
MDR-TB costs 10 times as much to treat, with a cure rate of just 60 percent. Ultimately one-quarter of MDR-TB victims die.
Increased attention to the problem has led to notable success. In the Orel and Tomsk regions of Russia, new MDR-TB cases have declined steeply since 2006, with less dramatic decreases in Estonia and Latvia.
About 5 percent of MDR-TB cases worldwide (and more than 10 percent in the former Soviet regions) are "extensively drug resistant," which means they are resistant to two alternative drugs, as well. Most of those patients die.
WHO estimates that to adequately treat MDR-TB in the 27 most-affected countries by 2015 will require about $3 billion a year; just $400,000 is being spent this year.