New influenza A(H1N1) virus infections in Spain, April-May 2009

On 25 April 2009, the World Health Organization (WHO) declared the outbreak of swine-origin influenza A(H1N1) virus infections, first reported by the United States (US) and Mexico, as a ’Public Health Event of International Concern‘ (PHEIC) under the International Health Regulations (2005). The pandemic alert level was raised from level 3 to level 4 on 27 April, and to level 5 on 29 April, after verification of sustained community-level outbreaks in at least two countries from the same WHO region.

On 26 April, epidemiological and laboratory investigations on three persons returning from Mexico were initiated in Spain. On 27 April, Spain reported the first laboratory-confirmed case of the new influenza A(H1N1) virus infection in Europe, in a traveller returning from Mexico. Since then, the number of confirmed cases in Spain has risen continuously and reached a total of 98 as of 11 May 2009.