Re-emergence and Amplification of Tuberculosis in the Canadian Arctic

• Published in: Journal of Infectious Diseases
• Main Authors: Lee, Robyn S., Radomski, Nicolas, Proulx, Jean-Francois, Manry, Jeremy, McIntosh, Fiona, Desjardins, Francine, Soualhine, Hafid, Domenech, Pilar, Reed, Michael B., Menzies, Dick, Behr, Marcel A.
• Format: Text
• Language: English
• Published: Oxford University Press 2015
• Subjects: MAJOR ARTICLE; Arctic
• Online Access: http://jid.oxfordjournals.org/cgi/content/short/jiv011v1; https://doi.org/10.1093/infdis/jiv011

Background. Between November 2011 and November 2012, a Canadian village of 933 persons had 50 culture-positive cases of tuberculosis, with 49 sharing the same genotype. Methods. We performed Illumina-based whole-genome sequencing on Mycobacterium tuberculosis isolates from this village, during and before the outbreak. Phylogenetic trees were generated using the maximum likelihood method. Results. Three distinct genotypes were identified. Strain I (n = 7) was isolated in 1991–1996. Strain II (n = 8) was isolated in 1996–2004. Strain III (n = 62) first appeared in 2007 and did not arise from strain I or II. Within strain III, there were 3 related but distinct clusters: IIIA, IIIB, and IIIC. Between 2007 and 2010, cluster IIIA predominated (11 of 22 vs 2 of 40; P < .001), whereas in 2011–2012 clusters IIIB (n = 18) and IIIC (n = 20) predominated over cluster IIIA (n = 11). Combined evolutionary and epidemiologic analysis of strain III cases revealed that the outbreak in 2011–2012 was the result of ≥6 temporally staggered events, spanning from 1 reactivation case to a point-source outbreak of 20 cases. Conclusions. After the disappearance of 2 strains of M. tuberculosis in this village, its reemergence in 2007 was followed by an epidemiologic amplification, affecting >5% of the population.