Influenza A (H1N1) 2009 surveillance on Mayotte island: the challenge of setting up a new system facing the pandemic

In response to the threat of the pandemic influenza A (H1N1) 2009 virus in Mayotte Island, influenza surveillance needed to be set up in a matter of weeks, to detect the introduction of the pandemic virus and monitor its spread and impact on public health. Surveillance was based on different systems, including a sentinel practitioner network for influenza-like illness, surveillance of the activity at the hospital emergency departments, virological surveillance, surveillance of severe and fatal cases, and data collection on sale of antipyretic and anti-viral drugs. Despite some weaknesses of the surveillance, results showed a good correlation between all systems, describing an epidemic period of approximately 8-9 weeks, with a peak between weeks 37 and 40, followed by a rapid decrease. Besides allowing monitoring and describing the impact of pandemic H1N1 2009 virus in Mayotte, the surveillance system provided an opportunity to create networks and globally strengthened surveillance of infectious diseases in the Island.