CDC Flu Update: Activity Increasing Slightly, Puerto Rico Has High ILI Activity

According to the CDC's FluView report for the week ending Dec. 3, 2016 (week 48), flu activity increased slightly, but remains low overall in the continental United States. Influenza A (H3) viruses were most commonly reported during week 48. While the timing of influenza activity varies and is unpredictable, flu activity is expected to increase in the coming weeks. 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.

For the week ending December 3, the proportion of people seeing their health care provider for influenza-like illness (ILI) was 1.8%. This is below the national baseline of 2.2%. Two regions (Region 2 and 4) reported ILI at or above their region-specific baseline level.

Puerto Rico experienced high ILI activity. New York City and four states (Colorado, Georgia, Louisiana, and Nevada) experienced low ILI activity. 46 states 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.

Widespread influenza activity was reported by Puerto Rico. Regional influenza activity was reported by Guam and two states (Alabama and North Carolina). Local flu activity was reported by 19 states (Arizona, Connecticut, Delaware, Indiana, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Minnesota, Nevada, New Hampshire, Ohio, Oklahoma, Oregon, Pennsylvania, Texas, Virginia, and Washington). Sporadic flu activity was reported by the U.S. Virgin Islands and 28 states (Alaska, Arkansas, California, Colorado, Florida, Georgia, Hawaii, Idaho, Illinois, Iowa, Kansas, Michigan, Mississippi, Missouri, Montana, Nebraska, New Jersey, New Mexico, New York, North Dakota, South Carolina, South Dakota, Tennessee, Utah, Vermont, West Virginia, Wisconsin, and Wyoming). No flu activity was reported by one state (Rhode Island). The District of Columbia did not report. Geographic spread data show how many areas within a state or territory are seeing flu activity.

Influenza-associated hospitalization data from the Influenza Hospitalization Surveillance Network (FluSurv-NET) for the 2016-2017 influenza season will be updated weekly starting later this season.

Due to data processing problems, the National Center for Health Statistics (NCHS) mortality surveillance data for the week ending November 19, 2016 (week 46) will not be published this week. 

No influenza-associated pediatric deaths for the 2016-2017 season have been reported to CDC.

Nationally, the percentage of respiratory specimens testing positive for influenza viruses in clinical laboratories during the week ending December 3 was 3.5%.

Regionally, the three week average percent of specimens testing positive for influenza in clinical laboratories ranged from 0.9% to 8.7%.

The most frequently identified influenza virus type reported by public health laboratories during the week ending December 3 was influenza A viruses, with influenza A (H3) viruses predominating.   During the week ending December 3, 141 (91.6%) of the 154 influenza-positive tests reported to CDC by public health laboratories were influenza A viruses and 13 (8.4%) were influenza B viruses. Of the 118 influenza A viruses that were subtyped, 112 (94.9%) were H3 viruses and 6 (5.1%) were (H1N1)pdm09 viruses.

Since Oct. 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 Oct. 1, 2016, CDC tested 156 specimens (24 influenza A (H1N1)pdm09, 104 influenza A (H3N2), and 28 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.

Source: CDC