Risk of Travelling to the Country of Origin for Tuberculosis Among Immigrants Living in a Low-incidence Country

Setting: Two thirds of tuberculosis (TB) patients in the Netherlands are foreign-born.

Objective: To determine if travelling to the country of origin is a risk factor for TB among two different immigrant groups that have lived in the Netherlands for at least 2 years.

Design: In this unmatched case-control study, the frequency and duration of travel to the country of origin in the preceding 12 months were compared between adult Moroccan and Turkish TB patients and community controls.

Results: Moroccan patients had travelled more often (26/32 = 81%) in the preceding year than Moroccan controls (472/816 = 58%). The travel-associated odds ratio (OR) for TB among Moroccans was 3.2 (95%CI 1.3-7.7), and increased to 17.2 (95%CI 3.7-79) when the cumulative duration of travel exceeded 3 months. The corresponding population fraction of Moroccan TB cases attributable to recent travel was 56% (95%CI 19-71). Among Turkish immigrants TB was not associated with travel (OR 0.9, 95%CI 0.3-2.4).

Conclusion: Travel to the country of origin was a risk factor for TB among Moroccans, but not among Turkish people living in the Netherlands. The difference in travel-associated OR between these two immigrant groups is probably related to differences in TB incidence in these countries.