Present registration figures reflect an increasing proportion of non-Western allochtones in the national TB incidence. A difference in age and sex distribution occurs between cases of Western and non-Western origin.

In the Western population, TB occurs especially in elderly men (sex ratio 2,4) and is mainly due to reactivation of dormant TB bacilli, when resistance is diminished.

In the non-Western population, TB shows 2 incidence peaks:

In 25-35 year age group with equal sex distribution and due to development of active TB soon after immigration and living under adverse living conditions;