Emerging Infectious Diseases
Volume 16, Number 9–September 2010
http://www.cdc.gov/ncidod/EID/index.htm

Letters
Mobile Messaging as Surveillance Tool during Pandemic (H1N1) 2009, Mexico
M. Lajous et al.

To the Editor: Pandemic (H1N1) 2009 highlighted challenges faced by disease surveillance systems. New approaches to complement traditional surveillance are needed, and new technologies provide new opportunities. We evaluated cell phone technology for surveillance of influenza outbreaks during the outbreak of pandemic (H1N1) 2009 in 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 (online Technical Appendix Figure 1). 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).
Of 70,856 responses received, 56,551 (78.1%) were unique mobile numbers (5.8% response rate; only the first response was used). Within 3 hours, 53% of responses were received and by 24 hours, 89% were received. Mean (SD) age of respondents was 25.2 (10.4) years (online Technical Appendix Table). A total of 9,333 persons reported ILI and 49.3% had severe symptoms. Mean number of other persons with ILI in the household was 1.6 among respondents reporting severe disease and 0.3 among those with nonsevere disease (p<0.0001, by t test)…