According to the CDC's FluView report for the week ending Jan. 28, 2017 (week 4), flu activity continues to increase and is widespread in most of the United States. Also, CDC reported seven 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 seven consecutive weeks so far this season. Influenza A (H3) viruses continue to predominate. 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 Jan. 28, the proportion of people seeing their health care provider for influenza-like illness (ILI) increased to 3.9%. This remains above the national baseline of 2.2%. All 10 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 15 states (Alabama, Arkansas, Georgia, Indiana, Kansas, Kentucky, Louisiana, Missouri, New Jersey, New York, Oklahoma, Pennsylvania, South Carolina, Tennessee, and Wyoming) experienced high ILI activity. Puerto Rico and 11 states (California, Hawaii, Illinois, Iowa, Maryland, Minnesota, North Carolina, North Dakota, South Dakota, Texas, and Virginia) experienced moderate ILI activity. 14 states (Alaska, Arizona, Colorado, Connecticut, Massachusetts, Michigan, Mississippi, Nebraska, Nevada, New Mexico, Oregon, Rhode Island, Utah, and Wisconsin )experienced low ILI activity. 10 states (Delaware, Florida, Idaho, Maine, Montana, New Hampshire, Ohio, 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 40 states (Alabama, Alaska, Arkansas, California, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Texas, Virginia, Washington, Wisconsin, and Wyoming). Regional influenza activity was reported by Guam and nine states (Arizona, Colorado, Hawaii, Michigan, North Carolina, Tennessee, Utah, Vermont, and West Virginia). Local influenza activity was reported by the District of Columbia and one state (Indiana). No 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 5,683 laboratory-confirmed influenza-associated hospitalizations have been reported. This translates to a cumulative overall rate of 20.3 hospitalizations per 100,000 people in the United States. This is lower than the hospitalization rate at this time (48.3 per 100,000) during the 2014-2015 flu season, when influenza A (H3N2) viruses also predominated. 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. The hospitalization rate among people 65 years and older is 94.8 per 100,000. This is the highest rate of any age group. The hospitalization rates for people 65 and older for the same week during the 2014-2015 and 2012-2013 flu seasons were 239.3 per 100,000 and 135 per 100,000 respectively. The 2014-2015 and 2012-2013 flu seasons were the last influenza A (H3N2)-predominant seasons in the United States.
The hospitalization rate among adults 50-64 years is 19.9 per 100,000. During 2014-2015 and 2012-2013 flu seasons, the hospitalization rate for that age group for the same week was 38 per 100,000 and 28.1 per 100,000 respectively.
The hospitalization rate among children younger than 5 years is 11.0 per 100,000. During 2014-2015 and 2012-2013 flu seasons, the hospitalization rates for people in that age group for the same week were 42 per 100,000 population and 41.8 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.
Mortality Surveillance: Due to data processing problems, the National Center for Health Statistics (NCHS) mortality surveillance data for the week ending January 14, 2017 (week 2) will not be published this week.
Pediatric Deaths: Seven influenza-associated pediatric deaths are being reported by CDC for the week ending January 28, 2017.
Three deaths were associated with an influenza A (H3) virus and occurred during weeks 1, 2, and 4 (the weeks ending January 7, 14, and 28, 2017, respectively).
Three deaths were associated with an influenza A virus for which no subtyping was performed and occurred during weeks 1, 3, and 4 (the weeks ending January 7, 21, and 28, 2017, respectively).
One death was associated with an influenza B virus and occurred during week 3 (the week ending January 21, 2017).
A total of 15 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 January 28 was 18.0%.
Regionally, the three week average percent of specimens testing positive for influenza in clinical laboratories ranged from 12.5% to 26.2%.
During the week ending January 28, of the 4,786 (18.0%) influenza-positive tests reported to CDC by clinical laboratories, 4,227 (88.3%) were influenza A viruses and 559 (11.7%) were influenza B viruses.
The most frequently identified influenza virus type reported by public health laboratories during the week ending January 28 was influenza A viruses, with influenza A (H3) viruses predominating.
During the week ending January 28, 1,239 (93.4%) of the 1,327 influenza-positive tests reported to CDC by public health laboratories were influenza A viruses and 88 (6.6%) were influenza B viruses. Of the 1,191 influenza A viruses that were subtyped, 1,170 (98.2%) were H3 viruses and 21 (1.8%) 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 794 specimens (75 influenza A (H1N1)pdm09, 572 influenza A (H3N2), and 147 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.