A cluster of multidrug-resistant Mycobacterium tuberculosis among patients arriving in Europe from the Horn of Africa: A molecular epidemiological study by Walker, T, Merker, M, Knoblauch, A, Helbling, P, Schoch, O, van der Werf, M, Kranzer, K, Fiebig, L, Kröger, S, Haas, W, Hoffmann, H, Indra, A, Egli, A, Cirillo, D, Robert, J, Rogers, T, Groenheit, R, Mengshoel, A, Mathys, V, Haanperä, M, Soolingen, D, Niemann, S, Böttger, E, Keller, P