Nearly one in four inpatients in a rural South African area could be infected with the multidrug-resistant TB (MDR-TB) by the end of 2012, while close to half would be carrying almost incurable drug-resistant XDR-TB strains of the disease.
An article published in The Lancet last week used epidemiological modelling to predict the transmission of drug resistant TB in Tugela Ferry, a rural district in KwaZulu-Natal where the first South African diagnoses of XDR-TB were made.
Mortality among XDR patients in that first outbreak at Tugela Ferry was close to 98%, with an average life span of just 16 days after their sputum was collected for testing. This mortality rate was boosted because people were only diagnosed only when they were very sick — but XDR-TB is almost impossible to treat with the drugs currently available. Such strains of TB usually result from incomplete treatment of ‘normal†TB and, in South Africa, are detected mainly in people with Aids. Many people likely to be carrying drug-resistant TB are, however, not diagnosed because the strain is kept inactive by healthy immune systems.
The XDR-TB outbreak in Tugela Ferry was driven by nosocomial infections — infections that occur in hospitals among patients or healthcare workers.
The model, created by Sanjay Basu from the Yale University School of Medicine and his co-authors, estimates that 29% of TB inpatients at Tugela Ferry have XDR-TB, while just more than half have variants of the pathogen that have at least some multidrug resistance.
They estimate that transmission in hospitals is responsible for about 90% of XDR-TB infections in the area.
But the drug-resistant pathogens are escaping from hospitals, and by 2012 60% of XDR-TB infections are expected to occur in the Tugela Ferry community.
The aim of the research published in The Lancet was to assess which forms of prevention could be most effective in curbing the spread of drug-resistant TB.
Researchers concluded: ‘A combination of infection control strategies that can be rapidly implemented in South African district hospitals — improved natural ventilation, reduced hospitalisation with the provision of outpatient therapy, mask use, rapid drug-susceptibility testing, hospital-based HIV testing with antiretroviral therapy and isolation of patients in five-bed units — could avert nearly half of XDR tuberculosis cases in Tugela Ferry over the next five years.â€
The authors are careful to emphasise the limitations of their work and stress the need for further research — but they say their work highlights the need for immediate action against the almost untreatable disease.