What the CDC is saying about the FLU
U.S. Situation Update
Percentage of Visits for
Influenza-like Illness (ILI)
Pneumonia and Influenza
Mortality for 122 Cities
Influenza-Associated Pediatric Mortality
Geographic Spread of Influenza
Influenza Positive Tests Reported to CDC
Key Flu Indicators
The United States is having an early flu season with most of the country now experiencing high levels of influenza-like-illness (ILI). In this week’s FluView report, some key flu activity indicators continued to rise, while others fell. It’s too soon to say exactly what this means; but some regions may have peaked, while other parts of the country are still on the upswing. This FluView update contains data for the week between December 30, 2012 and January 5, 2013.
Below is a summary of the key indicators:
The proportion of people seeing their health care provider for influenza-like illness (ILI) decreased from 6.0% to 4.3% for the week ending in January 5, but remains above the national baseline for the fifth consecutive week.
Twenty-four states and New York City are now reporting high ILI activity. Last week 29 states reported high ILI activity. Additionally, 16 are reporting moderate levels of ILI activity; an increase from 9 states in the prior week. States reporting high ILI activity for the week ending January 5, 2013 include Alabama, Colorado, Delaware, Georgia, Illinois, Iowa, Kansas, Louisiana, Michigan, Minnesota, Mississippi, Missouri, New Jersey, New Mexico, North Carolina, North Dakota, Oklahoma, Pennsylvania, Rhode Island, Tennessee, Texas, Utah, Virginia, and West Virginia.
Forty-seven states reported widespread geographic influenza activity for the week between December 30, 2012 and January 5, 2013. This is an increase from 41 states in the previous week. Geographic Spread data are based on assessments made by each state health department and show how many areas within a state or territory are seeing flu activity. The assessments made by each state health department are based on the detection of outbreaks of flu, increases in the percent of people visiting the doctor with flu-like symptoms, and patients with laboratory-confirmed influenza.
Since October 1, 2012, 3,710 laboratory-confirmed influenza-associated hospitalizations have been reported; an increase of 1,443 hospitalizations from the previous week. This translates to a rate of 13.3 influenza-associated hospitalizations per 100,000 people in the United States.
Influenza-associated hospitalizations are highest among people 65 and older. Of the 3,710 influenza-associated hospitalizations that have been reported this season, 46% have been among people 65 and older.
Hospitalization data are collected from 15 states to calculate a rate of laboratory-confirmed influenza-associated hospitalizations that is reasonably representative of the nation. These data do not reflect the actual total number of influenza-associated hospitalizations in the United States.
The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Mortality Reporting System is now slightly above the epidemic threshold for the first time this season.
Two influenza-related pediatric deaths were reported during the week between December 30 and January 5. One of the deaths was associated with an influenza A (H3) virus, and one was associated with an influenza A virus of unknown subtype. This brings the total number of influenza-associated pediatric deaths reported to CDC for 2012-2013 to 20. Additional information regarding pediatric deaths is available through FluView Interactive.
Nationally, the percentage of respiratory specimens testing positive for influenza in the United States during the week ending January 5, 2012 decreased from 35.2% in the previous week to 32.8% (Last week CDC reported 31.6% positive. This number increased after additional reports were submitted.)
Influenza A (H3N2), 2009 influenza A (H1N1), and influenza B viruses have all been identified in the U.S. this season. During the week ending January 5, 2013, 3,369 of the 4,222 influenza positive tests reported to CDC were influenza A and 853 were influenza B viruses. Of the 1,586 influenza A viruses that were subtyped, 98% were H3 viruses and 2% were 2009 H1N1 viruses.
Since October 1, 2012, CDC has antigenically characterized 521 influenza viruses, including 17 2009 influenza A (H1N1) viruses, 327 influenza A (H3N2) viruses and 177 influenza B viruses.
All 17 of the 2009 influenza A (H1N1) viruses were characterized as A/California/7/2009-like. This is the influenza A (H1N1) component of the Northern Hemisphere vaccine for the 2012-2013 season.
Of the 327 influenza A (H3N2) viruses, 325 (99%) were characterized as A/Victoria/361/2011-like. This is the influenza A (H3N2) component of the Northern Hemisphere influenza vaccine for the 2012-2013 season.
Approximately 67% of the 177 influenza B viruses belonged to the B/Yamagata lineage of viruses, and were characterized as B/Wisconsin/1/2010-like, the influenza B component for the 2012-2013 Northern Hemisphere influenza vaccine. The remaining 33% of the tested influenza B viruses belonged to the B/Victoria lineage of viruses.
Since October 1, 2012, CDC has tested 70 2009 influenza A (H1N1), 600 influenza A (H3N2), and 230 influenza B virus isolates for resistance to neuraminidase inhibitors this season. The tested viruses showed susceptibility to the antiviral drugs oseltamivir and zanamivir. High levels of resistance to the adamantanes (amantadine and rimantadine) persist among 2009 influenza A (H1N1) and A (H3N2) viruses. Adamantanes are not effective against influenza B viruses.
FluView is available – and past issues are archived – on the CDC website.
Note: As a result of the end of year holidays and elevated influenza activity, some surveillance sites may be experiencing longer than normal reporting delays. As such, data is likely to change as additional reports are received. The most up to date data for all weeks during the 2012-13 season can be found on the current FluView webpage.