Re-emergence and Amplification of Tuberculosis in the Canadian Arctic
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 b...
Published in: | Journal of Infectious Diseases |
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Main Authors: | , , , , , , , , , , |
Format: | Text |
Language: | English |
Published: |
Oxford University Press
2015
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Subjects: | |
Online Access: | http://jid.oxfordjournals.org/cgi/content/short/jiv011v1 https://doi.org/10.1093/infdis/jiv011 |
Summary: | 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. |
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