Addressing the Threat of Drug-Resistant Tuberculosis A Realistic Assessment of the Challenge: Workshop Summary (2009) / Chapter Skim
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2 The Global Spread of Multidrug-Resistant and Extensively Drug-Resistant Tuberculosis
2 The Global Spread of Multidrug-Resistant and Extensively Drug-Resistant Tuberculosis
Pages 19-34
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From page 19... ...
, or 4.8 percent, were MDR TB, and about 40,000 (or 0.4 percent) were XDR TB (Nunn, 2008)
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At the beginning of an epidemic, when many of those cases arise from people who fail therapy and amplify their drug resistance, the estimates will be especially low. Later, when transmission of drug resistance dominates most of those cases, the reported MDR TB rates will be higher.
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From page 21... ...
(The data on total cases and deaths are from WHO, 2008a; the number of MDR TB cases is from WHO, 2008b; the deaths from MDR and XDR TB were estimated by Nunn's team from published literature using the case numbers listed in the table; and the number of XDR TB cases [according to the revised October 2006 definition of XDR TB] was estimated from the MDR TB number listed in the table using the percentages from CDC, 2006.)
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From page 22... ...
. Nunn presented data comparing Estonia and Tomsk Oblasts following investments in TB and MDR TB control.
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National Surveillance System (collected during 1993–2004) ; samples taken from a cohort of MDR TB patients in Latvia's National MDR TB Registry during 2000–2002; and samples from South Korea's National Reference Laboratory.
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. Lack of Adequate Treatments Of even greater concern is that only about 10 percent of MDR TB patients are receiving any treatment, and only about 3 percent are being
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MDR TB is increasing in several countries and decreasing in others. But MDR rates among new cases are approaching 25 percent in many Eastern European countries, and XDR TB is clearly emerging.
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< 3% 3–6% > 6% No data FIGuRE 2-4 Percentage of MDR TB among new TB cases (1994–2007)
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Ben Amor further argued that countries identified as having the capability to conduct drug resistance surveys (WHO, 1997, 2000, 2004, 2008b) are more likely to have a well-functioning national TB program, laboratory structure, and transport network and therefore lower rates of MDR TB than those countries without these capabilities.
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From page 28... ...
; the second map represents data from the fourth WHO/IUATLD global report, published in 2008 (WHO, 2008b) , as well as other sources; and the last map is based on a formula developed by Zignol et al., 2006, to estimate the MDR TB rate in countries in which a drug resistance survey was never conducted.
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From page 29... ...
The incidence of MDR TB, by Friedland's calculation, is 100 per 100,000 population, much higher even than nonresistant TB in most parts of the world. Among MDR and XDR TB patients, the rate of HIV coinfection is greater than 90 percent.
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From page 30... ...
Neighboring countries -- Botswana, Mozambique, Lesotho, Namibia, and possibly Zimbabwe -- as well as all of the provinces in South Africa had reported cases as well. Figure 2-7 demonstrates the limited knowledge of the extent of MDR TB in KwaZulu-Natal.
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From page 31... ...
. Figure 2-8 shows the differences in mortality between MDR and XDR TB for Tugela Ferry; the top curve represents MDR TB mortality and the bottom curve XDR TB mortality.
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study, Van der Walt examined the drug resistance of baseline isolates among MDR TB patients enrolled in 2005 and found that 1 percent of the 800 cases screened were resistant to all drugs tested. She explained that, just as the emergence of XDR TB strains is in some cases a natural consequence of treating MDR TB patients, fully resistant strains can be expected to be the next threat, and may be a cause of XDR TB patients not responding well to treatment for XDR TB.
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Sloutsky also showed data from Tomsk prison collected before the beginning of the Institute's MDR TB treatment project, revealing that of 91 MDR TB patients tested, 2 had a fully drugresistant form of the disease (Sloutsky, 2008)
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From page 34... ...
• There is no rigorous, randomized evidence for the standard of care for MDR TB. Harrington noted that data are crucial to mounting the necessary response to the crisis.
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