WHO finds global rise in drug-resistant TB

Without proper public health funding and vigilant treatment practices, resistant strains of TB could continue to grow worldwide.

By Susan J. Landers — Posted April 14, 2008

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About 5% of the 9 million new cases of tuberculosis diagnosed each year worldwide are now resistant to multiple drugs, the highest rate ever recorded, according to a World Health Organization report.

The report, released on Feb. 26, also found that extensively drug-resistant TB, or XDR-TB, a virtually untreatable form of the disease, infects people in 45 countries. Although the United States has had relatively few cases of resistant strains of the disease -- 47 cases of XDR-TB were found in a retrospective analysis by the Centers for Disease Control and Prevention from 1993 to 2006 -- the potential for its spread is great.

Last summer, Atlanta lawyer Andrew Speaker traveled to Europe and back with a resistant strain thought at first to be XDR-TB. In December 2007, a woman infected with resistant TB flew from New Delhi to Chicago, setting off a search by public health officials to find and treat her fellow passengers.

TB that is resistant to at least isoniazid and rifampin -- two first-line drugs -- is identified as being multidrug resistant, or MDR-TB. While nonresistant TB can be treated effectively in 95% of patients with a six- to nine-month course of drugs, MDR-TB requires treatment for 18 to 24 months with second-line drugs that are considered much less effective. XDR-TB, which is resistant to first- and second-line drugs, is by far the most serious health threat, with a 25% mortality rate within one year in the U.S.

Vigilance is required on several fronts to prevent resistant strains of TB from becoming even more widespread, said several public health experts during a Feb. 27 hearing called by the House Subcommittee on Africa and Global Health.

But a March 17 WHO report, "Global Tuberculosis Control 2008," indicated that progress in detecting new cases slowed in 2006 because nations have been unable to sustain efforts they made in earlier years.

WHO Director-General Dr. Margaret Chan urged that public programs be strengthened. The report showed that TB budgets are expected to remain flat in 2008 in almost all the countries most heavily burdened by the disease.

The U.S. experience in previous years also can serve as an example of how inadequate funds and a lapse in attention can lead to outbreaks, said Centers for Disease Control and Prevention Director Julie Gerberding, MD, MPH, at the House hearing.

From 1953, when national surveillance began, until the mid-1980s, U.S. TB cases declined steadily, from about 83,000 to 22,000 new cases per year, she said. But in 1985, the CDC began documenting increases in the incidence of the disease that lasted until 1992. A key factor in this rise was the dismantling of TB programs, which occurred when health departments stopped receiving TB categorical funds from Congress and shifted those resources to other public health activities, Dr. Gerberding said.

Other factors came into play at that time: the HIV epidemic took off (the two diseases often form a lethal combination); immigration increased from countries with high TB rates; there was a lack of proper infection control in health care settings; and a widespread occurrence of MDR-TB occurred at a time when laboratory capacity to quickly identify such strains was inadequate, Dr. Gerberding said.

No quick fixes

The situation was remedied when Congress increased funding, appropriate drug regimens were prescribed, adequate laboratory capacity was in place and effective contact investigations were conducted, she said. MDR-TB cases fell from 483 in 1993 to 111 in 2006.

However, additional case-rate insights were provided in the CDC's March 21 Morbidity and Mortality Weekly Report. Specifically, in 2007, a total of 13,293 TB cases were reported in the United States. This amount marked a 4.2% decline from the 2006 rate of 4.4 cases per 100,000. Based on provisional data, the 2007 incidence rate was the lowest since national reporting began in 1953. But evidence also indicates that progress may be slowing. The average percentage decline from 1993 to 2000 was 7.3%. Between 2000 and 2007, this level fell to 3.8%. Foreign-born people as well as racial and ethnic minorities continue to bear a disproportionate burden of the disease in the United States.

"The cure for TB costs less than $20," said Rep. Donald Payne (D, N.J.), chair of the House panel. "If we do not support universal access to treatment on a global scale, not only do we risk the investments we are making in AIDS treatment overseas, we become vulnerable to an outbreak of MDR- and XDR-TB right here in the United States."

In recognition of the need for a multifaceted approach to halting the spread of MDR-TB, the AMA has called for routine TB testing of all HIV patients, separation of TB patients so the transmission of infection is less likely and rigorous adherence to treatment guidelines to prevent resistant strains from developing.

The WHO report, "Anti-Tuberculosis Drug Resistance in the World," is based on information collected between 2002 and 2006 on 90,000 TB patients in 81 countries. But because they lacked the resources, only six African nations were able to provide data for the survey, making it likely that the toll is even higher.

There are only 25 labs with the capacity to detect MDR-TB in all of Africa, and 19 of the labs are in South Africa, Payne noted.

The highest number of cases of multidrug-resistant strains was recorded in Baku, the capital of Azerbaijan, where nearly a quarter of all new TB cases were resistant. High rates were also found in Moldova, Ukraine and Uzbekistan.

"TB drug resistance needs a frontal assault," said Dr. Mario Raviglione, director of the WHO Stop TB Dept. "If countries and the international community fail to address it aggressively now, we will lose this battle," he said at a Feb. 26 press briefing to release the WHO report.

There was some good news, Dr. Raviglione noted. The Baltic nations, which had the highest number of MDR-TB cases 10 years ago, have reduced levels of the new cases and stabilized MDR-TB.

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Fewer Americans contracting TB

Although overall U.S. tuberculosis rates have declined, experts have marked a slowing of progress in recent years. Additionally, rates are persistently higher among foreign-born people (rates are per 100,000 population).

U.S.-born Foreign-born
Cases Per 100,000 Cases Per 100,000
1993 17,422 7.4 7,403 34.0
1994 16,171 6.8 7,741 34.6
1995 14,647 6.1 7,987 34.8
1996 13,315 5.6 7,726 31.5
1997 11,879 4.9 7,742 30.0
1998 10,632 4.4 7,599 28.9
1999 9,806 4.0 7,602 29.2
2000 8,648 3.5 7,619 27.3
2001 7,869 3.2 8,011 27.0
2002 7,281 2.9 7,718 25.4
2003 6,861 2.7 7,930 23.5
2004 6,656 2.6 7,822 23.2
2005 6,332 2.5 7,718 22.3
2006 5,934 2.3 7,799 22.0
2007 5,464 2.1 7,690 20.6

Note: Data for 2007 are provisional.

Source: Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention, March 21

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External links

"Anti-Tuberculosis Drug Resistance in the World," World Health Organization, Feb. 26 (link)

"Global Tuberculosis Control 2008, WHO, March 17 (link)

"Trends in tuberculosis -- United States, 2007," Morbidity and Mortality Weekly Report, March 21 (link)

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