Situation Update: Summary of Weekly FluView Report
U.S. Situation Update
Key Flu Indicators
According to the FluView report for the week ending May 13, 2017 (week 19), flu activity continues to decrease in the United States. Levels of flu-like illness have been below the national baseline for five weeks now. The 2016-2017 flu season is winding down. No states are reporting widespread activity at the time, but 5 states and Guam continue to report regional flu activity and another flu-related pediatric death was reported. This brings the total number of flu deaths in children reported to CDC that occurred during this season to 92. Sporadic flu activity may continue for a number of weeks. While influenza A (H3N2) viruses have been most common overall this season, influenza B viruses accounted for 51% of the viruses reported by public health laboratories during week 19. Interim vaccine effectiveness (VE) estimates indicate flu vaccines this season 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. Vaccination efforts should continue for as long as influenza viruses are circulating. Below is a summary of the key flu indicators for the week ending May 13, 2017:
- Influenza-like Illness Surveillance: For the week ending May 13 the proportion of people seeing their health care provider for influenza-like illness (ILI) was 1.3% and has now been below the national baseline of 2.2% for the fifth consecutive week. All 10 regions reported a proportion of outpatient visits for ILI below their region-specific baseline levels. For the 2016-2017 season, ILI was at or above baseline for 17 consecutive weeks. 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. Additional ILINet data, including data for previous seasons, can be found at http://gis.cdc.gov/grasp/fluview/fluportaldashboard.html.
- Influenza-like Illness State Activity Indicator Map: No states experienced high or moderate ILI activity. One state (Arizona) experienced low ILI activity. New York City, Puerto Rico and 47 states (Alabama, Arkansas, California, Colorado, Delaware, Florida, Georgia, Hawaii, 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, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, and Wyoming) experienced minimal ILI activity. The District of Columbia and two states (Alaska and Connecticut) 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. Additional data, including data for previous seasons, can be found at https://gis.cdc.gov/grasp/fluview/main.html
- Geographic Spread of Influenza Viruses: No states experienced widespread influenza activity. Regional influenza activity was reported by Guam and 5 states (Arizona, Connecticut, Maine, New Hampshire, and South Carolina). Local influenza activity was reported by Puerto Rico and 8 states (Alaska, California, Hawaii, Louisiana, New Jersey, New York, Ohio, and Washington). Sporadic activity was reported by the District of Columbia and 36 states (Alabama, Arkansas, Colorado, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kentucky, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Mexico, North Carolina, North Dakota, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, West Virginia, Wisconsin, and Wyoming). No influenza activity was reported by the U.S. Virgin Islands and one state (Kansas). 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: As of May 13, 2017, 18,118 laboratory-confirmed influenza-associated hospitalizations occurring between October 1, 2016, and April 30, 2017, have been reported through the Influenza Hospitalization Surveillance Network (FluSurv-NET). This translates to a cumulative overall rate of 64.7 hospitalizations per 100,000 people in the United States so far this season. This is higher than the cumulative hospitalization rate for the 2012-2013 flu season (44.0 per 100,000), when influenza A (H3N2) viruses also predominated, and is slightly higher than the cumulative hospitalization rate during 2014-2015 (64.1 per 100,000) which also was an H3N2 predominant season.
- The hospitalization rate among people 65 years and older is 288.8 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 183.9 per 100,000. For week 17 during 2014-2015, it was 308.8 per 100,000.
- The hospitalization rate among adults 50-64 years is 64.6 per 100,000. This is the highest hospitalization rate ever observed for this age group since this type of surveillance began. During the 2012-2013 and 2014-2015 flu seasons, the hospitalization rate for that age group for the same week was 40.9 per 100,000 and 53.4 per 100,000 respectively.
- The hospitalization rate among children younger than 5 years is 45.0 per 100,000. During the 2012-2013 and 2014-2015 flu seasons, the hospitalization rate for that age group for the same week was 67.0 per 100,000 and 57.2 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 6.1% for the week ending April 29, 2017 (week 17). This percentage is below the epidemic threshold of 7.0% for week 17 in the National Center for Health Statistics (NCHS) Mortality Surveillance System. The weekly percentage of deaths attributed to P&I was at or exceeded the epidemic threshold for 12 consecutive weeks this season.
- Region and state-specific data are available at http//gis.cdc.gov/grasp/fluview/mortality.html.
- Pediatric Deaths:
- One influenza-associated pediatric death is being reported by CDC for the week ending May 13, 2017.
- This death was associated with an influenza B virus and occurred during week 5 (the week ending February 4, 2017).
- A total of 92 influenza-associated pediatric deaths have been reported for the 2016-2017 season.
- Additional information on pediatric deaths for the 2016-2017 season and previous seasons is 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 May 13 was 4.4%.
- Regionally, the three week average percent of specimens testing positive for influenza in clinical laboratories ranged from 2.7% to 10.1%.
- During the week ending May 13, of the 415 (4.4%) influenza-positive tests reported to CDC by clinical laboratories, 103 (24.8%) were influenza A viruses and 312 (75.2%) were influenza B viruses.
- While influenza A (H3N2) viruses have predominated this season, the most frequently identified influenza virus type reported by public health laboratories since mid-March has been influenza B viruses.
- During the week ending May 13, 40 (49.4%) of the 81 influenza-positive tests reported to CDC by public health laboratories were influenza A viruses and 41 (50.6%) were influenza B viruses. Of the 36 influenza A viruses that were subtyped, 35 (97.2%) were H3N2 viruses and 1 (2.8%) was a (H1N1)pdm09 virus.
- Additional virologic data, including data for previous seasons, can be found at http://gis.cdc.gov/grasp/fluview/fluportaldashboard.html and http://gis.cdc.gov/grasp/fluview/flu_by_age_virus.html.
- 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 3,339 specimens (317 influenza A (H1N1)pdm09, 2,233 influenza A (H3N2), and 789 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.
Note: Delays in reporting may mean that data changes over time. The most up-to-date data for all weeks during the 2016-2017 season can be found on the current FluView.
- Page last reviewed: May 19, 2017
- Page last updated: May 19, 2017
- Content source:
- Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases (NCIRD)
- Page maintained by: Office of the Associate Director for Communication, Digital Media Branch, Division of Public Affairs