Survey of Mexican cell users in H1N1 pandemic had low response rate, but responses were quick
THURSDAY, Aug. 12 (HealthDay News) -- A survey invitation sent to hundreds of thousands of cell phone subscribers in Mexico during the 2009 H1N1 pandemic demonstrates a new model for enlisting new technology for surveillance during outbreaks of infectious disease, according to a letter published in the September issue of Emerging Infectious Diseases.
Martin Lajous, M.D., of the National Institute of Public Health in Cuernavaca, Mexico, and colleagues sent text messages to a random sample of 982,708 cell phones on May 12, 2009, inviting their participation in a survey on influenza-like illness (ILI) during the preceding month. They assessed date of fever onset, severity, number of household members afflicted, and other factors.
Overall, the authors received 70,856 responses, 56,551 of which were unique mobile numbers, a 5.8 percent response rate. Eighty-nine percent of responses were received within 24 hours -- 53 percent within three hours. A total of 9,333 persons reported ILI, with 49.3 percent reporting severe symptoms. The number of other household members with ILI among those reporting severe disease was a mean 1.6, and a mean 0.3 among those with non-severe disease. The mean age of respondents was 25.2 years. As the survey sample was unlikely to be representative of the total population, no estimates of disease incidence in the total population were made.
"Efficient estimation of extent of disease caused by a novel infectious agent may be costly and logistically difficult. When carefully deployed, unstructured supplementary service data surveys may be a practical, low-cost, and timely complement to traditional surveillance," the authors write.
Telefonica-Movistar donated the survey as well as technical and logistical support in conducting it.
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