CDC Flu Update: Activity is Widespread

According to the CDC's FluView report for the week ending Feb. 11, 2017 (week 6), flu activity continues to increase and is widespread in most of the United States. Also, CDC reported nine additional flu-associated pediatric deaths for the 2016-2017 season. The proportion of people seeing their healthcare provider for influenza-like-illness (ILI) has been at or above the national baseline for nine consecutive weeks so far this season. Influenza A (H3) viruses continue to predominate. Based on early estimates, flu vaccines this season have reduced a vaccinated person’s risk of getting sick and having to go to the doctor because of flu by about half (48%). CDC recommends annual flu vaccination for everyone 6 months of age and older. Anyone who has not gotten vaccinated yet this season should get vaccinated now.

Influenza-like Illness Surveillance: For the week ending February 11, the proportion of people seeing their health care provider for influenza-like illness (ILI) increased to 5.2%. This remains above the national baseline of 2.2%. All ten regions reported ILI at or above their region-specific baseline level. For the last 15 seasons, the average duration of a flu season by this measure has been 13 weeks, with a range from one week to 20 weeks.

Influenza-like Illness State Activity Indicator Map: New York City and 28 states (Alabama, Arkansas, Connecticut, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Minnesota, Mississippi, Missouri, New Jersey, New Mexico, New York, North Carolina, North Dakota, Oklahoma, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Virginia, and Wyoming) experienced high ILI activity. Puerto Rico and 7 states (Alaska, Massachusetts, Michigan, Nebraska, Ohio, Oregon, and Wisconsin) experienced moderate ILI activity.  Six states (Arizona, California, Colorado, Florida, Hawaii, and Nevada) experienced low ILI activity. Nine states (Delaware, Idaho, Maine, Montana, New Hampshire, Utah, Vermont, Washington, and West Virginia) experienced minimal ILI activity. The District of Columbia did not have sufficient data to calculate an activity level. ILI activity data indicate the amount of flu-like illness that is occurring in each state.

Geographic Spread of Influenza Viruses: Widespread influenza activity was reported by Puerto Rico and 46 states (Alabama, Alaska, Arizona, Arkansas, California, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Vermont, Virginia, Washington, West Virginia, Wisconsin, and Wyoming).  Regional influenza activity was reported by Guam and four states ((Colorado, Hawaii, Oregon, and Utah). Local influenza activity was reported by the District of Columbia. Sporadic influenza activity was reported by the U.S. Virgin Islands. Geographic spread data show how many areas within a state or territory are seeing flu activity.

Flu-Associated Hospitalizations: Since October 1, 2016, a total of 8,222 laboratory-confirmed influenza-associated hospitalizations have been reported. This translates to a cumulative overall rate of 29.4 hospitalizations per 100,000 people in the United States. This is lower than the hospitalization rate at this time (35.1 per 100,000) during the 2012-2013 flu season, when influenza A (H3N2) viruses also predominated. The 2012-2013 flu season was a recent influenza A (H3N2)-predominant season in the United States. Influenza A (H3N2) viruses also predominated during the 2014- 2015 flu season, but more than 70% of the H3N2 viruses circulating that season were different or "drifted" from the H3N2 vaccine virus.
The hospitalization rate among people 65 years and older is 136.6 per 100,000. This is the highest rate of any age group. The hospitalization rate for people 65 and older for the same week during the 2012-2013 flu season was 154.9 per 100,000.
The hospitalization rate among adults 50-64 years is 28.5 per 100,000. During 2012-2013 flu season, the hospitalization rate for that age group for the same week was 32.0 per 100,000 respectively.
The hospitalization rate among children younger than 5 years is 16.9 per 100,000. During 2012-2013 flu season, the hospitalization rate for people in that age group for the same week was 48.8 per 100,000 respectively.
During most seasons, children younger than 5 years and adults 65 years and older have the highest hospitalization rates. Hospitalization data are collected from 13 states and represent approximately 9% of the total U.S. population. The number of hospitalizations reported does not reflect the actual total number of influenza-associated hospitalizations in the United States. Additional data, including hospitalization rates during other influenza seasons, can be found at http://gis.cdc.gov/GRASP/Fluview/FluHospRates.html and http://gis.cdc.gov/grasp/fluview/FluHospChars.html.

Mortality Surveillance:  The proportion of deaths attributed to pneumonia and influenza (P&I) was 7.8% for the week ending January 28, 2017 (week 4). This percentage is above the epidemic threshold of 7.5% for week 4 in the National Center for Health Statistics (NCHS) Mortality Surveillance System.

Pediatric Deaths: Nine influenza-associated pediatric deaths are being reported by CDC for the week ending February 11, 2017.
Six deaths were associated with an influenza A (H3) virus and occurred during weeks 3, 4, 5, and 6 (the weeks ending January 21, January 28, February 4, and February 11, 2017, respectively.
Two deaths were associated with an influenza A virus for which no subtyping was performed and occurred during weeks 1 and 5 (the weeks ending January 7, and February 4, 2017).
One death was associated with an influenza B virus and occurred during week 5 (the week ending February 4, 2017).
A total of 29 influenza-associated pediatric deaths have been reported for the 2016-2017 season.
Additional information on pediatric deaths for the 2016-2017 season is now available on FluView Interactive at: https://gis.cdc.gov/GRASP/Fluview/PedFluDeath.html.

Laboratory Data: Nationally, the percentage of respiratory specimens testing positive for influenza viruses in clinical laboratories during the week ending February 11 was 24.2%.
Regionally, the three week average percent of specimens testing positive for influenza in clinical laboratories ranged from 12.6% to 29.4%.
During the week ending February 11, of the 8,498 (24.2%) influenza-positive tests reported to CDC by clinical laboratories, 7,079 (83.3%) were influenza A viruses and 1,419 (16.7%) were influenza B viruses.
The most frequently identified influenza virus type reported by public health laboratories during the week ending February 11 was influenza A viruses, with influenza A (H3) viruses predominating. 
During the week ending February 11, 1,528 (88.2%) of the 1,732 influenza-positive tests reported to CDC by public health laboratories were influenza A viruses and 204 (11.8%) were influenza B viruses. Of the 1,460 influenza A viruses that were subtyped, 1,430 (97.9%) were H3 viruses and 30 (2.1%) were (H1N1)pdm09 viruses.
Since October 1, 2016, antigenic and/or genetic characterization shows that the majority of the tested viruses remain similar to the recommended components of the 2016-2017 Northern Hemisphere vaccines.
Since October 1, 2016, CDC tested 1,104 specimens (117 influenza A (H1N1)pdm09, 752 influenza A (H3N2), and 235 influenza B viruses) for resistance to the neuraminidase inhibitors antiviral drugs. None of the tested viruses were found to be resistant to oseltamivir, zanamivir, or peramivir.

Source: CDC