We obtained patient age (years), date of symptoms onset, and reporting department (n = 24) and province (n = 134) for ILI and laboratory-confirmed influenza A/H1N1 cases reported between May 1 and December 31, 2009 . We also obtained 2009 population size and density (people/km 2 ) estimates for Peru's provinces and departments, using the National Institute of Statistics and Informatics (http://proyectos.inei.gob.pe/mapas/ bid).