2009-2010 influenza surveillance summaries

• Emergency department (ED) visits for influenza like illness (ILI) have held steady for over three months, after declining from a peak in fall.
• No laboratory-confirmed influenza hospitalizations with onset after the week ending 2/6/10 have been reported. All laboratory-confirmed influenza hospitalizations with onset of illness in February have been influenza B.
• No laboratory-confirmed influenza deaths have occurred in King County residents since mid-February.
• The percentage of specimens testing positive for influenza from our outpatient surveillance system is below the average proportion observed at this time of year.
• The percentage of rapid antigen tests positive for influenza is below the average proportion observed this time of year.
• Thirteen long-term care facilities reported cases of influenza like illness in their facilities from mid-October through early January. No reports of influenza like illness in long-term care facilities have been received since early January.
• School absenteeism has been low and stable in recent weeks, with the majority of schools reporting <10% of students absent. Some schools were closed for all or part of the week ending 2/20/10. Average absenteeism increased for the week ending 2/20/10 for all schools but most markedly for high schools, a pattern seen during school breaks in the past.

See current surveillance and testing guidelines for 2009 H1N1 influenza.