Migration and tuberculosis transmission in Hamburg, Germany: insights from 25 years of molecular epidemiology.

Migration increased genetic diversity of Mycobacterium tuberculosis in Hamburg but did not significantly change local transmission patterns, which remained lineage-specific.

• Why it matters: Understanding how imported strains influence TB transmission is crucial for controlling outbreaks in low-incidence regions, especially as migration alters population dynamics.
• What they did: Whole genome sequencing of 3,131 strains over 25 years revealed shifts in lineage distribution linked to patient origins, with detailed analysis of sublineage transmission potential.
• The result: Findings show that successful transmission is driven by established L4 sublineages, supporting the idea that locally adapted strains sustain TB spread despite increased diversity from migration.