estimated one-third of the world's population has tuberculosis
infection of the lungs. Although the disease is curable,
the widespread use and misuse of medication has led to the
emergence of multidrug-resistant strains of TB.
data from the World Health Organization (WHO), Christopher
Dye and Brian Williams looked at TB rates in 10 groups of
countries. They found that except in Russia, strains of
drug-sensitive and drug-resistant TB are reproducing less
than before. The findings, which appear in the October 21,
2009 online edition of Science
Translational Medicine, published by the American
Association for the Advancement of Science (AAAS), indicate
that current efforts to slow the spread of multidrug-resistant
TB are working.
An infected person spreads TB by coughing; the number of
secondary infections caused by a given infected person --
a value called "R" -- determines how fast TB spreads
throughout the population. If R can be kept to a value of
less than 1 by means of rapid diagnosis and treatment, the
disease will eventually burn itself out.
The study authors determined the values of R for TB strains
that were sensitive or resistant to 2 key anti-TB drugs
in 20 European countries, the United Kingdom, the United
States, Hong Kong, and Russia, and analyzed this data with
a computer model describing the spread of disease.
The results indicate that, with the exception of Russia,
the value of R for each of the drug-resistant strains tested
in each country is less than 1.
The authors noted that their conclusions must be verified
and expanded with more data from a wider range of countries
including India and China, where the number of new multidrug-resistant
TB cases each year is highest. They also stated that in
order to reach the goal of TB elimination by mid-century,
more intensive control efforts will be needed, based on
Office of HIV/AIDS, Tuberculosis, Malaria and Neglected
Tropical Diseases, World Health Organization, Geneva, Switzerland;
South African Centre for Epidemiological Modelling and Analysis,
Matieland, Stellenbosch, South Africa.
Dye and BG Williams. Slow Elimination of Multidrug-Resistant
Tuberculosis. Science Translational Medicine 1(3). October
21, 2009 (online edition). (Abstract).