Influenza-like Illness Surveillance on the California-Mexico Border, 2004-2009

Region-spanning national borders are conducive to the migration of infectious diseases. Since 2004, the Naval Health Research Center, in concert with health officials of San Diego and Imperial counties, has collaborated with the Secretary of Health, Mexico and the US Centers for Disease Control and Prevention to conduct respiratory disease surveillance in the US-Mexico border region. Demographic and symptom information and respiratory swabs were collected from enrollees who met the case definition for influenza-like illness (ILI). Between 2004 and 2009, 1855 individuals were sampled at clinics near the US-Mexico border in California and Baja California. The most frequent pathogen identified was influenza (25% of ILI cases), with those aged 6?15 years the most frequently affected. In April 2009, a young female participant from Imperial County, California, became among the first documented cases of pandemic influenza A/H1N1. A number of other viral and bacterial respiratory pathogens were identified from submitted samples, including adenovirus, parainfluenza viruses, respiratory syncytial virus, Streptoccocus pneumoniae, S. pyogenes, Haemophilus influenzae and beta-hemolytic streptococci. These findings illustrate the importance of disease surveillance in areas near national borders. Pub. in Influenza and Other Respiratory Viruses, p1-8, Journal, 2011.