Measles genotypes D4 and G3 reintroduced by multiple foci after 15 years without measles virus circulation, Gipuzkoa, the Basque Country, Spain, March to June 2011 Cilla, G and Montes, M and Artieda, J and Piñeiro, L and Arriola, L and Pérez-Trallero, E, Eurosurveillance, 16, 19997 (2011), https://doi.org/10.2807/ese.16.43.19997-en