XDR tuberculosis has been reported in 37 countries (as of May 2007), and has been identified in all regions of the world. South Africa has had the largest cluster of XDR cases, with incidence in every region of the country. Over 200 cases have been reported from 40 sites in the KwaZulu-Natal province alone, the first 53 of which were in the rural town of Tugela Ferry.
Sanjay Basu, Yale University School of Medicine, New Haven, CT, USA, and colleagues combined computer modelling with data from a multi-year epidemiological study to investigate the effect of administrative, environmental ,and personal infection control measures on the epidemic trajectory of XDR tuberculosis in Tugela Ferry. The model simulated inpatient airborne tuberculosis infection, community tuberculosis transmission, and the effect of HIV and anti-retroviral therapy. The model was found to be more than 95% accurate at estimating the course of the disease when evaluated against the latest data from South Africa.
They found that in no new interventions are introduced, around 1300 cases of XDR tuberculosis could occur in the Tugela Ferry area by 2012, more than half are which are likely to be transmitted within the hospital. Use of masks alone would prevent fewer than 10% of cases in the general epidemic, but could, vitally, prevent a large proportion of cases in hospital staff. Combined use of masks, reduced hospitalisation time and a shift to outpatient therphy could prevent nearly a third of cases; and combining this approach with improved ventilation, rapid drug resistance testing, HIV treatment, and tuberculosis isolation facilities could avert nearly half (48%) of cases.
However, the authors add that lengthy hospitalisation or involuntary detention in the absence of sufficient isolation facilities could actually increase the incidence of XDR tuberculosis, since the increased risk of nosocomial transmission outweighed the impact of decreased community-based transmission resulting from these policies.
They conclude by saying their current projections highlight the need for immediate action in addressing the XDR tuberculosis epidemic. The burden of XDR tuberculosis on the health system is already high in this area, and is expected to rise substantially over the next few years.
They say: “Effective hospital-based strategies to limit the transmission of XDR tuberculosis are within reach, even in resource-limited settings…such comprehensive programmes should be rapidly implemented throughout KwaZulu-Natal and the rest of South Africa. Addition community-based strategies should also be developed in parallel, since hospital-based efforts alone might not fully curtail XDR tuberculosis transmission.”
In an accompanying Comment, Dr Travis Porco, University of California, San Francisco, CA, USA, and Dr Wayne Getz, University of California, Berkeley, CA, USA, say: “Multidrug and extensive drug resistance are monsters of our own creation. They might be with us longer than we think and might need us to spend more than governments or institutions are willing or able to pay. Although scientific warnings are often ignored until too late, effective interventions for the control of XDR tuberculosis in Africa are national and international responsibilities, and the world community ignores this message at great peril.”
*Nosocomial infections are those which are contracted as result of a patients treatment in a hospital or healthcare service unit, but secondary to the patients original condition.
**XDR tuberculosis is defined as tuberculosis which is resitant to isoniazid, rifampicin, any fluoroquinolone, and at least one of three injectable second-line drugs (ie. amikacin, kanamycin, or capreomycin).
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