2011-2012 Flu Season Draws to a Close
Recently, the Centers for Disease Control and Prevention issued the final full influenza surveillance report for the 2011-2012 season.
The report — titled “FluView” — shows that influenza activity in the United States is minimal across most of the country, wrapping up a season that began late and was mild compared to most previous seasons for which surveillance data is available.
In fact, the season set a new record for the lowest and shortest peak for influenza-like-illness since this type of surveillance began.
Influenza-like-illness (ILI) in the United States typically begins to increase in late December or early January and peaks in February most commonly. This season, ILI remained low through February and did not exceed baseline — and then only slightly -- until mid-March. ILI stayed above baseline for just one week in March and did not exceed baseline again.
According CDC’s Dr. Joseph Bresee, “This is the first time since CDC started this kind of influenza-like-surveillance (ILI) that the percentage of patient visits for ILI was elevated for only one week of the season.” Dr. Bresee is Chief of the Epidemiology and Prevention Branch in CDC’s Influenza Division.
In past seasons, ILI has remained above baseline for between 8 and 20 weeks, with an average of 13 weeks at or above baseline each season since this type of surveillance began in 1997-1998. Bresee adds, “In terms of ILI, this not only the shortest time we were above baseline, but it’s also the lowest ‘peak’ ever recorded.”
Other key flu indicators were low this season as well. As of May 25, 2012, 26 pediatric deaths occurring during the 2011-2012 season had been reported to CDC; this is the lowest number of pediatric deaths reported during a season since such record-keeping began. These are deaths in children younger than 18 who test positive for influenza. These deaths have been legally reportable by states to CDC since 2004.