CDC Flu Update: Activity Low Overall in Continental U.S.

According to the first full FluView report from the CDC for the 2016-2017 season, flu activity is low overall in the continental United States, with only Guam reporting widespread flu activity. Influenza A (H3) viruses were most common during week 40. While the timing of influenza activity varies and is unpredictable, flu activity often begins to increase in October. CDC recommends that everyone 6 months of age and older get an annual flu vaccine before the end of October, if possible.

For the week ending October 8, the proportion of people seeing their health care provider for influenza-like illness (ILI) was 1.1%. This is below the national baseline of 2.2%. All 10 regions reported ILI below their region-specific baseline levels. New York City and all 50 states experienced minimal ILI activity. The District of Columbia and Puerto Rico 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 flu activity was reported by Guam. Local flu activity was reported by Puerto Rico and one state (New Hampshire). Sporadic flu activity was reported by the U.S. Virgin Islands and 36 states (Alaska, Arizona, California, Colorado, Connecticut, Florida, Georgia, Hawaii, Idaho, Iowa, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nevada, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, South Dakota, Tennessee, Texas, Utah, Washington, West Virginia, Wisconsin, and Wyoming). No activity was reported by the District of Columbia and 13 states (Alabama, Arkansas, Delaware, Illinois, Indiana, Kansas, Mississippi, Nebraska, North Carolina, Rhode Island, South Carolina, Vermont, and Virginia). 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.

The proportion of deaths attributed to pneumonia and influenza (P&I) was 5.4% for the week ending September 24, 2016 (week 38). This percentage is below the epidemic threshold of 6.3% for week 38 in the NCHS Mortality Surveillance System.

CDC is no longer publishing mortality data from the 122 Cities Mortality Reporting System (122 CMRS) in the weekly MMWR Table 3 or the FluView Weekly U.S. Influenza Surveillance Report. The 122 CMRS is being retired. Influenza mortality data will continue to be collected through the National Center for Health Statistics (NCHS) mortality surveillance system. This data will be published in the weekly MMWR Table 3 and in FluView going forward.

No influenza-associated pediatric deaths were reported to CDC this week.

Nationally, the percentage of respiratory specimens testing positive for influenza viruses in clinical laboratories during the week ending October 8 was 1.7%.

Regional clinical laboratory data percentages ranged from 0.1% to 4.2% for the most recent three weeks.

No genetic or antigenic characterization data is available yet for viruses collected after October 1, 2016. This information will be updated weekly beginning later in the season.

For viruses collected between May 22–Sept 30, 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.

No antiviral resistance data is available for specimens collected after October 1, 2016. From May 22 to September 30, 2016, however, CDC tested 159 specimens (14 influenza A (H1N1)pdm09, 84 influenza A (H3N2), and 61 influenza B viruses) for resistance to the neuraminidase inhibitors antiviral drugs. While the vast majority of the viruses that have been tested in recent months are sensitive to oseltamivir, zanamivir, and peramivir, one (7.1%) influenza A (H1N1)pdm09 viruses showed resistance to oseltamivir and peramivir. A total of 12 influenza A (H1N1)pdm09 viruses were tested for zanamivir susceptibility and all were susceptible. None of the 84 influenza A (H3) and 61 influenza B viruses were found to be resistant to either oseltamivir, zanamivir, or peramivir. Antiviral resistance data will be updated weekly starting later in the season.

Source: CDC