According to this week’s FluView report, seasonal influenza activity increased slightly in the United States. The proportion of people seeing their healthcare provider for influenza-like-illness (ILI) is above the national baseline for the first time this season, however this increase may be influenced in part by a reduction in routine health care visits during the Thanksgiving holidays. Twenty-one states are now reporting regional or local flu activity(Alaska, Arizona, California, Connecticut, Florida, Georgia, Idaho, Kentucky, Louisiana, Massachusetts, New Hampshire, New Jersey, New York, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, Tennessee, Texas, and Utah). That means those states are seeing outbreaks of flu and laboratory-confirmed flu in at least one or less than half of the regions of the state, respectively. However 28 states, the District of Columbia, Puerto Rico, and the U.S. Virgin Islands continue to report only sporadic flu activity, which means those states are seeing small numbers of flu or one laboratory confirmed flu outbreak. Influenza A(H1N1)pdm09 viruses have been the most commonly identified flu viruses since September 30, 2018. CDC also reported two additional flu-associated pediatric deaths for the 2018-2019 flu season. While activity is slowly increasing, it’s too early to say the 2018-2019 flu season has started.
An annual flu vaccine is the best way to protect against influenza and its potentially serious complications. There are many benefits to vaccination, including reducing the risk of flu illness, doctor’s visits, hospitalization, and even death in children. For anyone 6 months or older who has not yet been vaccinated this season, CDC recommends that they get vaccinated now. Below is a summary of the key flu indicators for the week ending November 24, 2018:
Influenza-like Illness Surveillance: For the week ending November 24 (week 47), the proportion of people seeing their health care provider for influenza-like illness (ILI) was 2.3% and is above the national baseline of 2.2%. Five of 10 regions (Regions 2, 4, 7, 8 and 9) reported a proportion of outpatient visits for ILI at or above their region-specific baseline level. The increase in the percentage of patient visits for ILI may be influenced in part by a reduction in routine health care visits during the Thanksgiving holidays, as has occurred in previous seasons. Additional ILINet data, including national, regional, and select state-level data for the current and previous seasons, can be found at http://gis.cdc.gov/grasp/fluview/fluportaldashboard.html.
Influenza-like Illness State Activity Indicator Map: Two states (Georgia and Louisiana) experienced high ILI activity. Three states (Alabama, Oklahoma, and Utah) experienced moderate ILI activity. New York City, the District of Columbia, Puerto Rico and eight states (Arizona, Arkansas, Colorado, Kentucky, Mississippi, New Jersey, South Carolina, and Virginia) experienced low ILI activity. 37 states experienced minimal ILI activity. Additional data, including data for previous seasons, can be found at https://gis.cdc.gov/grasp/fluview/main.html.
Geographic Spread of Influenza Viruses: Regional influenza activity was reported by five states (Connecticut, Kentucky, Massachusetts, Oregon, and Utah). Local influenza activity was reported by 16 states (Alaska, Arizona, California, Florida, Georgia, Idaho, Louisiana, New Hampshire, New Jersey, New York, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, and Texas). Sporadic influenza activity was reported by the District of Columbia, Puerto Rico, the U.S. Virgin Islands and 28 states (Alabama, Arkansas, Colorado, Delaware, Hawaii, Illinois, Indiana, Iowa, Kansas, Maine, Maryland, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Mexico, North Carolina, North Dakota, Rhode Island, South Dakota, Vermont, Washington, West Virginia, Wisconsin, and Wyoming). No influenza activity was reported by Guam and one state (Virginia). Geographic spread data show how many areas within a state or territory are seeing flu activity. Additional data are available at: https://gis.cdc.gov/grasp/fluview/FluView8.html.
Flu-Associated Hospitalizations: Reporting of influenza-associated hospitalization data from the Influenza Hospitalization Surveillance Network (FluSurv-NET) for the 2018-2019 influenza season will begin later this season. Additional data, including hospitalization rates during previous 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 5.8% during the week ending November 17, 2018 (week 46). This percentage is below the epidemic threshold of 6.4% for week 46 in the National Center for Health Statistics (NCHS) Mortality Surveillance System. Additional P&I mortality data for current and past seasons and by geography (national, HHS region, or state) are available at https://gis.cdc.gov/grasp/fluview/mortality.html
Pediatric Deaths: Two influenza-associated pediatric death were reported to CDC during week 47 (the week ending November 24, 2018).
One death was associated with an influenza A(H1N1)pdm09 virus and occurred during week 46 (the week ending November 17, 2018) and one death was associated with an influenza A(H3) virus and occurred during week 47 (the week ending November 24, 2018).
A total of five influenza-associated pediatric deaths have been reported for the 2018-2019 season.
Additional information on influenza-associated pediatric deaths reported during past seasons, including basic demographics, underlying conditions, bacterial co-infections, and place of death is available on FluView Interactive at: https://gis.cdc.gov/GRASP/Fluview/PedFluDeath.html. More detailed information about pediatric deaths reported during the current season will be available later in the season.
Nationally, the percentage of respiratory specimens testing positive for influenza viruses in clinical laboratories during the week ending November 24 was 2.4%.
Regionally, the three-week average percent of specimens testing positive for influenza in clinical laboratories ranged from 0.6% to 5.4%.
During the week ending November 24, of the 397 (2.4%) influenza-positive tests reported to CDC by clinical laboratories, 372 (93.7%) were influenza A viruses and 25 (6.3%) were influenza B viruses.
The most frequently identified influenza virus type reported by public health laboratories was influenza A(H1N1)pdm09 virus.
During the week ending November 24, 84 (95.5%) of the 88 influenza-positive tests reported to CDC by public health laboratories were influenza A viruses and 4 (4.5%) were influenza B viruses. Of the 72 influenza A viruses that were subtyped, 12 (16.7%) were H3N2 viruses and 60 (83.3%) were (H1N1)pdm09 viruses.
The majority of the influenza viruses collected from the United States during May 20 through November 24, 2018 were characterized antigenically and genetically as being similar to the cell-grown reference viruses representing the 2018–2019 Northern Hemisphere influenza vaccine viruses.
None of the viruses tested from May 20-November 24, 2018 were found to be resistant to oseltamivir, zanamivir, or peramivir.