The final weeks of 2019 saw high seasonal influenza activity across the United States, and the CDC said it continues to increase, according to the Weekly Influenza Surveillance Report for the week ending in December 28, 2019.1

So far during the 2019-2020 influenza season, the CDC estimates that there have been at least 6.4 million flu illnesses, resulting in 55,000 hospitalizations, and 2900 deaths. Of those, 27 pediatric deaths have been reported to the CDC, including 18 deaths associated with influenza B viruses, and 9 deaths caused by influenza A viruses.1

Outpatient visits for influenza-like illnesses (ILIs) and the percentage of respiratory specimens testing positive for influenza are similar to levels seen at the peak of previous seasons.1

For the week ending in December 28, 2019, visits to health care providers for ILIs increased from 5.1% to 6.9%. This percentage is above the national baseline of 2.4%. The percentage of respiratory specimens testing positive for influenza at clinical laboratories also increased during week 52, from 23% to 26.3%. All regions were above their baselines and continuing to increase, according to the report.1

The District of Columbia, New York City, Puerto Rico, and 34 states saw high ILI activity levels, while 9 states experienced moderate activity, and 5 states saw low activity. Only 2 states—Delaware and Idaho—reported minimal activity.1

Nationally, B/Victoria viruses are the most common, followed by A(H1N1)pdm09 viruses. The report noted that this finding is unusual for this time of year. The report added that B/Yamagata viruses are circulating at very low levels.1

The overall hospitalization rate for the season has also increased, from 9.2 per 100,000 people. This rate is similar to what has been documented at this time during previous seasons.1

Although the 2020 influenza season is expected to be strong, the CDC report noted that the percentage of deaths attributed to pneumonia and influenza is still below the epidemic threshold. The report also urged continued vaccination efforts, and added that antiviral medications are an important adjunct to flu vaccine in controlling the virus. More than 99% of the influenza viruses tested this season are susceptible to the 4 FDA-approved influenza antiviral medications recommended for use. 1

In addition, Walgreens has released their December report for their Flu Index, showing many states and markets with increased flu activity, and Nebraska and Tennessee having the most instances of the flu. This data shows a spike in most areas around Thanksgiving and holiday travel times. For the month of November, the top 10 states with Flu Activity were (in order): Nebraska, Tennessee, Texas, Virginia, Mississippi, New Mexico, Oklahoma, Kentucky, Louisiana, and Alabama. When analyzing the top Designated Market Areas (DMAs) with flu activity, the southern states continue to rank in the top 5, including Texas, Mississippi, and Tennessee. 2 

Editor's Note: This article was updated on January 7, 2020. 

REFERENCE
1. Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases. Weekly U.S. Influenza Surveillance Report, Key Updates for week 52 Ending December 28, 2019. CDC website. https://www.cdc.gov/flu/weekly/index.htm#ILIActivityMap. Accessed January 6, 2020.
2. Walgreens flu index December report shows majority of US experiencing high flu activity [news release]. Deerfield, Ill.; Walgreens Newsroom: January 6, 2020. https://www.businesswire.com/news/home/20200106005749/en/Walgreens-Flu-Index%C2%AE-December-Report-Shows-Majority. Accessed January 7, 2020.