I would like to say, "The immigrants come from Maghreb and sub-Saharan Africa." So far I have,
Les immigrés viennent du Maghreb et d'Afrique sub-saharienne.
The contracted article "du" makes sense here, but why is there no definite article before Afrique? I would expect to see either "du", "de la" or even "des" depending on gender and number. What is it that I am missing?