Mobile Messaging as Surveillance Tool during Pandemic (H1N1) 2009, Mexico

On May 12, 2009, at 2:20 PM, a random sample of 982,708 telephones from an 18 million nationwide network of mostly prepaid cell phones (1) received a text message invitation to a Ministry of Health survey. Influenza-like illness (ILI) in April, date of fever onset, severity, number of household members with ILI, age, influenza vaccination, household size, and number of children in each household were assessed (Technical Appendix Figure 1, www.cdc.gov/EID/content/pdfs/16/9/1488-Techapp.pdf). ILI was defined as fever and cough or sore throat, and severe ILI was defined as inability to work, study, or maintain family care. Unstructured supplementary service data, an interactive platform available on most cell phones, was used. We obtained daily counts of suspected and confirmed cases of pandemic (H1N1) 2009 from the nationwide clinic-based surveillance system Sistema Nacional de Vigilancia Epidemiológica (SINAVE) (2,3).