Control of TB epidemic requires more effective drugs, better tests, and focus on latent infection

06/06/05

ATLANTA--With approximately 9 million individuals expected to develop tuberculosis (TB) this year and more than 2 million expected to die from the disease, according to the World Health Organization, tuberculosis has become a global public health epidemic. In the U.S., although TB cases have declined since 1992, it remains a serious health problem in urban areas and among certain populations including some U.S.-born persons. The global TB epidemic increasingly impacts the U.S., where the majority of TB cases now occurring are among people born outside the country.

In an article in the Journal of the American Medical Association published on-line on Tuesday, June 7, clinician/researchers describe the most current effective treatments for both active TB and latent TB infection and the efforts underway to develop new drugs and more effective diagnostic tools. A stepped-up effort targeting programs to detect and treat the large number of people with latent TB infection who are at increased risk for progression to active TB is a strategy for enhancing TB control efforts in the U.S., the authors say.

Effective treatment of active TB requires a minimum of six to nine months of multi-drug therapy. To ensure successful completion of the therapy, these drugs should be administered by using "directly observed therapy," which requires that a health care worker give a patient the drugs then watch the patient swallow them. Directly observed therapy has been demonstrated to enhance completion and cure rates and reduce the risk of emergence of drug-resistant TB.

"Enhancing control of TB in the U.S. requires close collaboration between public health programs and private clinicians," says Henry Blumberg, MD, professor of medicine (infectious diseases) at Emory University School of Medicine, director of infection control at Atlanta's Grady Memorial Hospital and lead author of the JAMA paper. "Our goals with treatment are to cure patients, minimize the emergence of drug-resistant disease and prevent spread of disease within the community." Dr. Michael Leonard, assistant professor of medicine (infectious diseases) at Emory and medical consultant to the Georgia DHR TB Program was a co-author of the JAMA paper.

Persons who are infected with Mycobacterium tuberculosis, the organism that causes TB, but who have not developed active TB are deemed to have latent TB infection and are at risk for progression to active TB. Two broad categories of persons who should be targeted for testing for latent TB infection and then treated if they are found to have infection include: those likely to have been recently infected through contact with another person with active TB (TB is transmitted through an air-born route when someone with active pulmonary TB coughs), and persons at increased risk of progression to TB following infection because of other clinical conditions such as HIV, or because they are recent immigrants from countries with a high level of TB infection.

Treatment of latent TB infection is approximately 90 percent effective in patients who are compliant with the one-drug regimen over nine months; however the long time period involved and the lack of directly observed therapy (due to lack of resources to support this) means success often falls short.

New, more effective TB drugs, which currently are under development, are needed for treating multi-drug resistant cases of TB and also to shorten treatment in both active TB and latent TB infection, says Dr. Blumberg. Better diagnostic tests for latent TB infection to replace the tuberculin skin test also are needed to further enhance TB control (and subsequently TB elimination) efforts in the U.S. he says. Although new tests are under development and some preliminary results have been promising, further studies are needed to determine the ultimate utility of these newer diagnostic tests.

"Control of TB in the U.S. over the past decade has improved," Dr. Blumberg says, "but it remains a serious public health problem here and an enormous public health program globally. For better TB control in the U.S., a renewed focus on latent TB infection (both new diagnostics and treatment) is needed. From a global perspective, new drugs are needed for active TB (to shorten the course of therapy and for the treatment of multi-drug resistant TB), and the development of an effective TB vaccine is also critical to enhance global TB control efforts which impact control efforts in the U.S. as well.."

Source: Eurekalert & others

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