CDC Flu Update: 37 States Reporting Widespread Activity

According to the CDC's FluView report for the week ending Jan. 21, 2017 (week 3), flu activity continues to increase in the United States. The number of states reporting widespread flu activity increased from 29 states to 37 states. Also, CDC reported three additional flu-associated pediatric deaths for the 2016-2017 season. The proportion of people seeing their health care provider for influenza-like-illness (ILI) has been at or above the national baseline for six consecutive weeks so far this season. Influenza A (H3) viruses continue to predominate. Flu activity is expected to continue for several 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.

Influenza-like Illness Surveillance: For the week ending Jan. 21, the proportion of people seeing their health care provider for influenza-like illness (ILI) increased to 3.4%. This remains above the national baseline of 2.2%. All ten regions reported ILI at or above their region-specific baseline level. 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.

Influenza-like Illness State Activity Indicator Map: New York City and 10 states (Alabama, Georgia, Kansas, Louisiana, Minnesota, Missouri, New Jersey, Oklahoma, South Carolina, and Tennessee) experienced high ILI activity. 10 states (Arizona, Arkansas, Colorado, Kentucky, Mississippi, New Mexico, Utah, Virginia, Washington, and Wyoming) experienced moderate ILI activity. Puerto Rico and 17 states (Alaska, California, Florida, Hawaii, Idaho, Illinois, Iowa, Maryland, Michigan, Nebraska, Nevada, New York, North Carolina, Oregon, Pennsylvania, South Dakota, and Texas)experienced low ILI activity. 13 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.

Geographic Spread of Influenza Viruses: Widespread influenza activity was reported by Puerto Rico and 37 states (Alaska, California, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Iowa, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Texas, Virginia, Washington, Wisconsin, and Wyoming). Regional influenza activity was reported by Guam and 12 states (Alabama, Arizona, Arkansas, Colorado, Hawaii, Maine, Michigan, North Carolina, Tennessee, Utah, Vermont, and West Virginia). Local influenza activity was reported by the District of Columbia and one state (Indiana). No influenza activity was reported by the U.S. Virgin Islands. Geographic spread data show how many areas within a state or territory are seeing flu activity.

Flu-Associated Hospitalizations: Since October 1, 2016, a total of 4,317 laboratory-confirmed influenza-associated hospitalizations have been reported. This translates to a cumulative overall rate of 15.4 hospitalizations per 100,000 people in the United States. This is higher than the hospitalization rate at this time (2.5 per 100,000) last season, when influenza A (H1N1)pdm09 viruses predominated. 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. The highest hospitalization rates are among people 65 years and older (72.2 per 100,000), followed by adults 50-64 years (15.2 per 100,000) and children younger than 5 years (8.4 per 100,000). 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.

Mortality Surveillance: The proportion of deaths attributed to pneumonia and influenza (P&I) was 7.4% for the week ending January 7, 2017 (week 1). This percentage is above the epidemic threshold of 7.3% for week 1 in the National Center for Health Statistics (NCHS) Mortality Surveillance System.

Pediatric Deaths: Three influenza-associated pediatric deaths were reported to CDC during the week ending January 21, 2017.
Two deaths were associated with an influenza A (H3) virus and occurred during week 2 (the week ending January 14, 2017).
One death was associated with an influenza B virus and occurred during week 3 (the week ending January 21, 2017).
A total of 8 influenza-associated pediatric deaths have been reported for the 2016-2017 season.

Laboratory Data: Nationally, the percentage of respiratory specimens testing positive for influenza viruses in clinical laboratories during the week ending January 21 was 18.4%.
Regionally, the three week average percent of specimens testing positive for influenza in clinical laboratories ranged from 11.8% to 27.7%.
During the week ending Jan. 21, of the 4,813 (18.4%) influenza-positive tests reported to CDC by clinical laboratories, 4,306 (89.5%) were influenza A viruses and 507 (10.5%) were influenza B viruses.
The most frequently identified influenza virus type reported by public health laboratories during the week ending January 21 was influenza A viruses, with influenza A (H3) viruses predominating.
During the week ending Jan. 21, 1,072 (93.2%) of the 1,150 influenza-positive tests reported to CDC by public health laboratories were influenza A viruses and 78 (6.8%) were influenza B viruses. Of the 998 influenza A viruses that were subtyped, 980 (98.2%) were H3 viruses and 18 (1.8%) 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 680 specimens (66 influenza A (H1N1)pdm09, 488 influenza A (H3N2), and 126 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