CDC Flu Update: Activity Remains Elevated in Most of the U.S.

According to this week’s FluView report, seasonal influenza activity remains elevated in the United States and flu is widespread in most of the country. 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 12, 2019:

Influenza-like Illness Surveillance: For the week ending January 12 (week 2), the proportion of people seeing their health care provider for influenza-like illness (ILI) was 3.1%, 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: Nine states (Colorado, Connecticut, Georgia, Kentucky, Louisiana, New Hampshire, New Jersey, New Mexico, and Oklahoma) experienced high ILI activity. New York City and 13 states (Alabama, Arizona, Indiana, Kansas, Massachusetts, Maryland, Nevada, Pennsylvania, South Carolina, Texas, Utah, Virginia, and Vermont) experienced moderate ILI activity. 10 states (California, Illinois, Minnesota, Missouri, Mississippi, North Carolina, New York, Rhode Island, Washington, and Wisconsin) experienced low ILI activity. The District of Columbia, Puerto Rico, and 18 states (Alaska, Arkansas, Delaware, Florida, Hawaii, Idaho, Iowa, Maine, Michigan, Montana, North Dakota, Nebraska, Ohio, Oregon, South Dakota, Tennessee, 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 Guam and 30 states (Arizona, California, Colorado, Connecticut, Delaware, Florida, Idaho, Indiana, Kansas, Kentucky, Massachusetts, Minnesota, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Utah, Vermont, Virginia, and Wyoming). Regional influenza activity was reported by Puerto Rico and 16 states (Alabama, Arkansas, Georgia, Illinois, Iowa, Louisiana, Maine, Maryland, Michigan, Mississippi, Missouri, Montana, North Dakota, Texas, Washington, and Wisconsin). Local influenza activity was reported by three states (Alaska, Tennessee, and West Virginia). Sporadic influenza activity was reported by the District of Columbia, the U.S. Virgin Islands and one state (Hawaii). 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, 3,568 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 12.4 hospitalizations per 100,000 people in the United States.
The highest hospitalization rate is among adults aged 65 years and older (31.9 per 100,000) followed by children younger than 5 years (23.5 per 100,000), and adults aged 50-64 years (16.3 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 6.9% during the week ending January 5, 2019 (week 1). This percentage is below the epidemic threshold of 7.0% for week 1 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 2 (the week ending January 12, 2019).
Two deaths were associated with an influenza A(H1N1)pdm09 virus and occurred during weeks 52 and 2 (the weeks ending December 29, 2018 and January 12, 2019, respectively). One death was associated with an influenza A virus for which no subtyping was performed and occurred during week 52.
A total of 19 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 12 was 12.4%.
As of January 12, the highest proportion of specimens testing positive for flu viruses in clinical laboratories has been 16.7% (reported during the week ending December 29, 2018).
Regionally, the three-week average percent of specimens testing positive for influenza in clinical laboratories ranged from 9.2% to 17.3%.
During the week ending January 12, of the 3,856 (12.4%) influenza-positive tests reported to CDC by clinical laboratories, 3,730 (96.7%) were influenza A viruses and 126 (3.3%) 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 January 12, 743 (98.8%) of the 752 influenza-positive tests reported to CDC by public health laboratories were influenza A viruses and 9 (1.2%) were influenza B viruses. Of the 679 influenza A viruses that were subtyped, 74 (10.9%) were H3N2 viruses and 605 (89.1%) were (H1N1)pdm09 viruses.
The majority of the influenza viruses collected from the United States during September 30, 2018 through January 12, 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 October 1, 2018-January 12, 2019 were associated with highly reduced inhibition (resistance) to oseltamivir, zanamivir, or peramivir. One influenza A(H1N1)pdm09 virus (0.3%) was associated with reduced susceptibility to oseltamivir.

Source: CDC