Friday, May 15, 2009

FluView and Surveillance Data

On CDC's surveillance site, FluView, there is clear indication of a massive spike in flu cases, including seasonal flu as well as H1N1 (about a 50/50 breakdown). This is mostly an artifact of massive amounts of specimen testing. CDC tracks flu cases nationwide through two systems:
  1. One system is completely dependent on lab-based specimen testing. The FluView graph (below) represents this system. The late spike in 'cases' shown in week 17 is due to massive amounts of testing for all ILI in any clinical setting. This activity is affected acutely by media coverage and H1N1 concerns among the population.
  2. The second system uses an ILI network of 4500 providers nationwide providing information on how many people seek care at clinics for all causes and how many of those are presenting with ILI symptoms. This system is much less affected by public health messages or media coverage. Information on clusters of H1N1 in the SW and NW are based on this system. This information is also consistent with the number of school closures and other reports on H1N1 in those areas.

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