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Localized transmission significantly drives MDR-TB epidemic in Peru
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Local “hot spots” of increased risk appeared to play a key role in disease transmission during a multidrug-resistant tuberculosis epidemic in Lima, Peru, according to recent data.
In the population-based, prospective cohort study, researchers identified 3,286 patients aged older than 15 years with incident pulmonary tuberculosis (TB) diagnosed at one of 106 participating public health centers in Lima Ciudad and Lima Este between September 2009 and August 2012. Within 1 month of diagnosing TB in the index patients, the researchers visited their homes and asked all other household members to participate in a baseline assessment of TB infection and disease. These individuals were monitored for incident infection and disease for 12 months. Smear and culture were used to assess all index cases and suspected cases for TB disease. Using handheld GPS units, study nurses gathered spatial data on affected households. Strains were further tested from culture-confirmed cases for drug resistance, and extracted and genotyped DNA by 24-loci MIRU-VNTR. The researchers constructed maps illustrating per-capita rates of drug-resistant, drug-sensitive and MDR-TB at the health center level.
The overall per-capita incidence of culture-confirmed tuberculosis was 74.12 per 100,000 (95% CI, 71.59-76.61). There was significant geographic disparity in the per-capita rate of TB and the rate of MDR-TB across the 85 evaluated areas. Some health center catchment areas had especially high overall rates of TB and MDR-TB, and the most severely affected areas had per-capita disease rates that were much greater than those of the least affected area (Rate ratio = 89; 95% CI, 54-185). The researchers reported an average ratio of MDR to non-MDR cases of 0.12 (95% CI, 0.12-0.15).
Overall, 12 of 35 of the largest genotypic clusters demonstrated patterns of spatial aggregation, indicating localized transmission. However, the researchers sometimes observed that most cases of a particular genotype fell outside a highlighted area of genotype-specific risk.
“Our findings provide additional detail on the spatial distribution of MDR-TB and identify areas where transmission of particular genotypes appears to be spatially concentrated,” the researchers wrote. “We also expanded on the results of previous analyses of administrative data which raised concerns about elevated risk of transmitted MDR-TB risk in Lima Este. We found that the increased risk of MDR due to transmission associated with living in this area was comparable to the increased risk of MDR associated with previous TB treatment in the study population as a whole.” – by Jen Byrne
Disclosure: The researchers report no relevant financial disclosures.
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