Abstract
BackgroundTransmission patterns in high tuberculosis incidence areas in England are poorly understood but need elucidating to focus contact tracing. We study transmission within and between age, ethnic and immigrant groups using molecular data from the high incidence West Midlands region.MethodsIsolates from culture-confirmed tuberculosis cases during 2007–2011 were typed using 24-locus Mycobacterial Interspersed Repetitive Unit-Variable Number Tandem Repeats (MIRU-VNTR). We estimated the proportion of disease attributable to recent transmission, calculated the proportion of isolates matching those from the two preceding years (“retrospectively clustered”), and identified risk factors for retrospective clustering using multivariate analyses. We calculated the ratio (RCR) between the observed and expected proportion clustered retrospectively within or between age, ethnic and immigrant groups.ResultsOf the 2159 available genotypes (79% of culture-confirmed cases), 34% were attributed to recent transmission. The percentage retrospectively clustered decreased from 50 to 24% for 0–14 and ≥ 65 year olds respectively (p = 0.01) and was significantly lower for immigrants than the UK-born. Higher than expected clustering occurred within 15–24 year olds (RCR: 1.4 (95% CI: 1.1–1.8)), several ethnic groups, and between UK-born or long-term immigrants with the UK-born (RCR: 1.8 (95% CI: 1.1–2.4) and 1.6 (95% CI: 1.2–1.9) respectively).ConclusionsThis study is the first to consider “who clusters with whom” in a high incidence area in England, laying the foundation for future whole-genome sequencing work. The higher than expected clustering seen here suggests that preferential mixing between some age, ethnic and immigrant groups occurs; prioritising contact tracing to groups with which cases are most likely to cluster retrospectively could improve TB control.
Highlights
Transmission patterns in high tuberculosis incidence areas in England are poorly understood but need elucidating to focus contact tracing
Risk factors for retrospective clustering Of the 2159 cases analysed, 959 isolates (44%, 95% CI: 42– 46%) shared identical genotypes during 2007–11, comprising 225 clusters, with 119 including two cases and 77, 16 and 9 clusters with 3–5, 6–9 and 11–49 cases respectively
We found that retrospective clustering with pulmonary cases between some ethnic groups was over two-fold greater than expected, and more
Summary
Transmission patterns in high tuberculosis incidence areas in England are poorly understood but need elucidating to focus contact tracing. Molecular strain-typing data on “who is clustered with whom” may provide insight into transmission patterns. Molecular studies in England to date, based on MIRU-VNTR, have typically considered short time periods (2010–2012) [2, 3], the amount of household transmission and risk factors for clustering, but have not yet studied the characteristics of cases with whom different cases cluster. The latter depends largely on transmission patterns, and is affected by other factors, including disease susceptibility. This study considered a low tuberculosis incidence area (notification rate of 8/100000/year in 2016) and WGS has not yet been used in England to study M tuberculosis transmission in high incidence areas
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
