Hamburg TB study links migration to bacterial diversity
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Researchers in Hamburg, Germany, analysed over thirty years of tuberculosis data to understand how migration affects the spread of the disease.
Nicole Ullrich, Viola Dreyer, and Stefan Niemann led a team at the Research Center Borstel that sequenced the genomes of 3,131 tuberculosis bacteria collected from patients in Hamburg between 1997 and 2021. They combined this genomic information with patient demographics and Germany’s public health surveillance data to track how the bacterial population changed over time.
The study revealed that while migration increased the variety of tuberculosis bacterial lineages present in Hamburg, it did not significantly change how the disease spread. Lineage 4 bacteria remained the most common and continued to drive most local transmission, even as the proportion of patients born outside Germany increased. The researchers found 81 percent of identified transmission clusters contained Lineage 4 strains.
Further analysis showed certain sublineages within Lineage 4 are particularly successful at infecting people from diverse backgrounds, supporting the idea that locally adapted bacteria are most likely to spread. The team used a five-allele distance threshold to identify transmission chains, a conservative method ensuring accuracy in their findings. This long-term genomic surveillance provides a model for other cities to understand how migration impacts tuberculosis and to focus public health responses accordingly.
