CDC Flu Update: Seasonal Influenza Activity Remains Elevated

According to this week’s FluView report, seasonal influenza activity remains elevated in the United States. The number of states reporting widespread geographic flu activity went from 24 states during the last reporting week to 30 states. CDC also reported another three flu-associated pediatric deaths. H1N1 viruses have been the most commonly identified flu viruses nationally. However, H3N2 viruses have predominated in the southeastern region of the United States.

CDC expects flu activity to remain elevated for a number of weeks. 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. Flu vaccination also has been shown to reduce severity of illness among people who get vaccinated but still get sick. For anyone 6 months or older who has not yet been vaccinated this season, CDC recommends that they get vaccinated now. There also are flu antiviral drugs that can be used to treat flu illness. Below is a summary of the key flu indicators for the week ending January 5, 2019:

Influenza-like Illness Surveillance: For the week ending January 5 (week 1), the proportion of people seeing their health care provider for influenza-like illness (ILI) was 3.5%, which is above the national baseline of 2.2%. Over the past five flu seasons, the peak percent of visits due to ILI has ranged between 3.6% (2015-2016) and 7.5% (2017-2018). All 10 regions reported a proportion of outpatient visits for ILI at or above their region-specific baseline level. 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: New York City and 15 states (Alabama, Arizona, Colorado, Georgia, Kentucky, Louisiana, Maryland, Massachusetts, Nebraska, New Jersey, New Mexico, Oklahoma, South Carolina, Utah, and Virginia) experienced high ILI activity. 12 states (Connecticut, Illinois, Indiana, Kansas, Minnesota, Mississippi, Missouri, New York, North Carolina, Pennsylvania, Texas, and Vermont) experienced moderate ILI activity. The District of Columbia, Puerto Rico, and 8 states (Arkansas, California, Michigan, Nevada, Oregon, Rhode Island, Tennessee and Wisconsin) experienced low ILI activity. 15 states (Alaska, Delaware, Florida, Hawaii, Idaho, Iowa, Maine, Montana, New Hampshire, North Dakota, Ohio, South Dakota, Washington, West Virginia, and Wyoming) 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: Widespread influenza activity was reported by 30 states (Alabama, Arizona, California, Colorado, Connecticut, Delaware, Florida, Idaho, Indiana, Iowa, Kansas, Kentucky, Louisiana, Massachusetts, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Oregon, Pennsylvania, Rhode Island, South Carolina, Utah, Vermont, Virginia, and Wyoming). Regional influenza activity was reported by Puerto Rico and 17 states (Arkansas, Georgia, Illinois, Maine, Maryland, Michigan, Minnesota, Missouri, Montana, North Dakota, Oklahoma, South Dakota, Tennessee, Texas, Washington, West Virginia, and Wisconsin). Local influenza activity was reported by two states (Hawaii and Mississippi). Sporadic influenza activity was reported by the District of Columbia, the U.S. Virgin Islands and one state (Alaska). Guam did not report. 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: Since October 1, 2018, 2,616 laboratory-confirmed influenza-associated hospitalizations have now been reported through the Influenza Hospitalization Network (FluSurv-NET), a population-based surveillance network for laboratory-confirmed influenza-associated hospitalizations covering approximately 9% of the U.S. This translates to a cumulative overall rate of 9.1 hospitalizations per 100,000 people in the United States.
The highest hospitalization rate is among adults aged 65 years and older (22.9 per 100,000) followed by children younger than 5 years (19.1 per 100,000), and adults aged 50-64 years (11.5 per 100,000). During most seasons, adults 65 years and older have the highest hospitalization rates followed by young children.
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 6.4% during the week ending December 29, 2018 (week 52). This percentage is below the epidemic threshold of 7.0% for week 52 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: Three influenza-associated pediatric deaths were reported to CDC during week 1 (the week ending January 5, 2019). One death was associated with an influenza A(H3) virus, one death was associated with an influenza A(H1N1)pdm09 virus and one death was associated with an influenza A virus for which no subtyping was performed. All three deaths occurred during week 52 (the week ending December 29, 2018). A total of 16 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.

Laboratory Data:
Nationally, the percentage of respiratory specimens testing positive for influenza viruses in clinical laboratories during the week ending January 5 was 12.7%. Regionally, the three-week average percent of specimens testing positive for influenza in clinical laboratories ranged from 8.0% to 20.9%. During the week ending January 5, of the 4,460 (12.7%) influenza-positive tests reported to CDC by clinical laboratories, 4,347 (97.5%) were influenza A viruses and 113 (2.5%) 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 January 5, 440 (99.1%) of the 444 influenza-positive tests reported to CDC by public health laboratories were influenza A viruses and 4 (0.9%) were influenza B viruses. Of the 390 influenza A viruses that were subtyped, 68 (17.4%) were H3N2 viruses and 322 (82.6%) were (H1N1)pdm09 viruses. The majority of the influenza viruses collected from the United States during September 30, 2018 through January 5, 2019 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 September 30, 2019-January 5, 2019 were found to be resistant to oseltamivir, zanamivir, or peramivir.

Source: CDC