Key Flu Indicators

November 13, 2009, 11:30 AM

Each week CDC analyzes information about influenza disease activity in the United States and publishes findings of key flu indicators in a report called FluView.* During the week of November 1-7, 2009, a review of key indictors found that certain indicators declined, while others continued to rise. Overall, flu activity in the United Sates remained very high. Below is a summary of the most recent key indicators:

* Visits to doctors for influenza-like illness (ILI) nationally decreased this week over last week. This is the second week of national decreases in ILI after four consecutive weeks of sharp increases. (All regions but one showed declines in ILI. Region I (CT, ME, MA, NH, RI and VT) continues to show sharp increases in ILI activity. While ILI declined overall nationally, visits to doctors for influenza-like illness remain higher than what is seen during the peak of many regular flu seasons.
* Total influenza hospitalization rates for laboratory-confirmed flu continue to climb and remain higher than expected for this time of year. Hospitalization rates continue to be highest in younger populations with the highest hospitalization rate reported in children 0-4 years old.
* The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Report continues to increase and has been higher than what is expected for six weeks now. In addition, 35 flu-related pediatric deaths were reported this week: 26 of these deaths were associated with laboratory confirmed 2009 H1N1; eight were influenza A viruses, but were not subtyped; and one was an influenza B virus. Since April 2009, CDC has received reports of 156 laboratory-confirmed pediatric 2009 H1N1 deaths, one influenza B death, and another 23 pediatric deaths that were laboratory confirmed as influenza, but the flu virus subtype was not determined.
* Forty-six states are reporting widespread influenza activity at this time; a decline of two states over last week. They are: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, and Wyoming. This many reports of widespread activity at this time of year are unprecedented during seasonal flu.
* Almost all of the influenza viruses identified so far continue to be 2009 H1N1 influenza A viruses. These viruses remain similar to the virus chosen for the 2009 H1N1 vaccine, and remain susceptible to the antiviral drugs oseltamivir and zanamivir with rare exception

*All data are preliminary and may change as more reports are received.

—————————————————————————

2008-2009 Influenza Season Week 38 ending September 26, 2009

All data are preliminary and may change as more reports are received.

Synopsis:

During week 38 (September 20-26, 2009), influenza activity remained elevated in the U.S

• 2,126 (22.8%) specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division were positive for influenza.
• 99% of all subtyped influenza A viruses being reported to CDC were 2009 influenza A (H1N1) viruses.
• The proportion of deaths attributed to pneumonia and influenza (P&I) was below the epidemic threshold.
• Eleven influenza-associated pediatric deaths were reported and all eleven were associated with 2009 influenza A (H1N1) virus infection.
• The proportion of outpatient visits for influenza-like illness (ILI) was above the national baseline. Regions 2 through 10 reported ILI above region-specific baseline levels; only Region 1 was below its region-specific baseline.
• Twenty-seven states reported geographically widespread influenza activity, Guam and 18 states reported regional influenza activity, two states, the District of Columbia, and Puerto Rico reported local influenza activity, one state reported sporadic influenza activity, and the U.S. Virgin Islands and two states did not report.
• The 2009-10 influenza season officially begins October 4, 2009.

* HHS regions (Region 1: CT, ME, MA, NH, RI, VT; Region 2: NJ, NY, Puerto Rico, US Virgin Islands; Region 3: DE, DC, MD, PA, VA, WV; Region 4: AL, FL, GA, KY, MS, NC, SC, TN; Region 5: IL, IN, MI, MN, OH, WI; Region 6: AR, LA, NM, OK, TX; Region 7: IA, KS, MO, NE; Region 8: CO, MT, ND, SD, UT, WY; Region 9: AZ, CA, Guam, HI, NV; and Region 10: AK, ID, OR, WA)
† Elevated means the % of visits for ILI is at or above the national or region-specific baseline
‡ National data are for current week; regional data are for the most recent three weeks
§ Includes all 50 states, the District of Columbia, Guam, Puerto Rico, and U.S. Virgin Islands
¥ The majority of influenza A viruses that cannot be sub-typed as seasonal influenza viruses are 2009 A (H1N1) influenza viruses upon further testing