The effect of migration on the incidence and mortality of bloodstream infection: a Danish register-based cohort study.

Objectives: To investigate bloodstream infection (BSI) related to migrant status by comparing the incidence and mortality in migrants with that in non-migrants.

Methods: In this register-based cohort study we linked a cohort of migrants and non-migrants with a bacteraemia database covering two regions in Denmark. We included first-time BSI between January 2000 and December 2015 in individuals ≥18 years. Migrants were categorized according to status: refugees or family-reunified migrants. Incidence rate ratio and mortality rate ratio were analysed using Poisson regression.

Results: We identified 493 080 non-migrants, of which 3405 had BSI, and 80 740 migrants with 576 cases; of the latter, 40 222 were family-reunified migrants with 226 cases and 40 518 were refugees with 350 cases. Refugees had a higher risk of BSI than non-migrants (adjusted IRR 1.19, 95%CI 1.01-1.40). Family-reunified migrants and refugees had a higher risk of Gram-negative BSIs (adjusted IRR 1.23, 95%CI 1.00-1.51 and 1.57, 95%CI 1.32-1.86), respectively, and a lower risk of Gram-positive BSIs (adjusted IRR 0.65, 95%CI 0.51-0.83 and 0.77, 95%CI 0.63-0.95), respectively, compared to non-migrants. Originating from Southeast Asia and the Pacific was associated with an increased risk of BSI compared to non-migrants (adjusted IRR 1.26, 95%CI 1.07-1.49). We found no differences in the adjusted 30-day or 90-day mortality according to migrant status.

Conclusions: Vulnerability towards BSI differs according to migrant status. Refugees had a higher risk of BSI overall. Both refugees and family-reunified migrants had a higher incidence of Gram-negative BSI than non-migrants. Similarly, migrants from Southeast Asia and the Pacific had a higher risk of BSI than non-migrants.