Molecular Epidemiology of TB Lay Summary
In the last 10 years, there has been a rise in tuberculosis (TB) cases among Inuit in the Canadian Arctic. This study wanted to understand better the transmission of TB in this region using a technique known as whole-genome sequencing (WGS). WGS examines the composition of the TB bacteria’s genetic material. To do this, we studied samples from patients who had TB in the lungs, between 2009 and 2015, in Iqaluit
To better understand how TB was being transmitted between people, we calculated the number of transmission events between people using the genetic information from the bacteria that they were infected with and combined it with information collected by the health teams. We also added any locations that people with TB may have visited frequently. During the study period, we sequenced 140 TB bacteria from 135 TB cases. We identified 4 groups of transmission events, and all the bacteria originated from the same genetic ancestor. One group represented 62% of all cases sequenced during the study period meaning that they were all linked. One of the chains of transmissions started and spread from a homeless shelter. Another one of these spreading events was related to a non-sanctioned gambling house, resulting in even more transmission. We confirmed TB transmission from the homeless shelter to the non-shelter areas in Iqaluit. We developed an algorithm to determine transmission events and found that it had very good reproducibility.
In summary, our study suggests that socioeconomic factors, specifically residing in a homeless shelter and spending time in a gambling house, may explain the rise in TB cases in Iqaluit.