Extensively drug-resistant tuberculosis in sub-Saharan Africa: an emerging public-health concern.

The extensively drug-resistant tuberculosis (XDR-TB) categorisation has been developed as a phenotypic description of those TB strains that are resistant to most conventional anti-TB drugs. While widely accepted to have significant incidence in those areas, such as Eastern Europe, that have high levels of multidrug resistance, recent reports have described a cluster of XDR-TB cases in the KwaZulu-Natal province of South Africa. With very high case-fatality rates in this setting and a paucity of potential treatment options, concerns have grown about the possibility of an outbreak of highly lethal TB occurring in areas where TB prevalence, generally, is at its highest. In this article, we review previously documented case series of XDR-TB, and examine questions around the likelihood of rapid XDR-TB expansion in sub-Saharan Africa. We analyse how current TB control measures in the area might cope with such a challenge, and identify new areas for focus within the research and development community.