Although some regions within the former Soviet Union are beginning to stem epidemics of multi-drug resistant tuberculosis, 440,000 cases of multidrug-resistant (MDR) TB are estimated to have emerged worldwide in 2008, the World Health Organization said this week.
In its 2010 global report on MDR-TB surveillance and response, the World Health Organization (WHO) highlights successes in some of the worst-affected regions of Russia, as well as the Baltic states of Estonia and Latvia, where very high rates of MDR-TB have declined dramatically over the past five years as a result of aggressive intervention.
But WHO also notes that other regions continue to report very high rates of MDR TB. In north-western Russia (Archangelsk, Pskov and Murmansk) between 23 and 28% of all new TB cases were multi-drug resistant in 2008, the highest proportion ever reported anywhere in the world.
MDR and XDR TB were most widespread in Eastern Europe and Central Asia, and WHO reports that there are some indications from surveys in Latvia, Estonia, Lithuania, Moldova and Mozambique that people with HIV are more likely to have multi-drug resistant strains.
“If confirmed, such a finding could have significant implications for control of dual TB and HIV epidemics in sub-Saharan Africa,” the WHO report concludes. However they also note that only eleven countries were able to provide data on MDR-TB frequency in people with HIV, making it difficult to draw firm conclusions.
Nevertheless the WHO report notes that there are several good reasons for expecting MDR-TB rates to be higher in people living with HIV:
- High rates of injecting drug use and incarceration.
- Marginalisation and lack of access to medical care.
- Increased rates of hospitalisation in close proximity to other patients with MDR-TB, coupled with poor infection control in those facilities.
- Poor absorption of the TB drug rifampicin, leading to sub-optimal treatment and drug resistance.
WHO estimates that around 69,000 cases of MDR-TB occurred in Africa in 2008, but most went undiagnosed due to lack of diagnostic facilities. Half of the cases worldwide occurred in India and China.
WHO estimates that only 7% of MDR TB cases worldwide were diagnosed in 2008. WHO is currently working with the Foundation for Innovative New Diagnostics (FIND), the Stop TB Partnership's Global Drug Facility (GDF) and the Global Laboratory Initiative (GLI) with financial support from UNITAID in a partnership called EXPAND TB to upgrade laboratories and improve diagnosis.
TB bacteria are classified as multidrug-resistant if the two first-line TB drugs isoniazid and rifampicin fail to check their growth. They are classified as extensively drug-resistant (XDR) if they are also resistant to the effects of injectable drugs used in second-line treatment as well as the entire fluoroquinolone class of antibiotics.
Drug resistance most often arises because of missed doses or failure to finish a course of treatment, but may be worsened by lack of drug susceptibility testing. If physicians do not know that patients have drug resistance, they are likely to prescribe drugs that intensify resistance.
Further information
World Health Organization Multidrug and Extensively Drug-Resistant Tuberculosis: 2010 Global Report on Surveillance and Response. March 18, 2010.