The flu has been on the rise across the United States for four weeks in a row, according to the Walgreens Flu Index.
Flu activity soared 52% for the week ending Jan. 18 over the previous week and continued rising for the next four weeks.
But data from the week ending Feb. 8, with the most recent results, showed a small 1.6% increase in the average overall flu activity.
"Flu season is in full swing," said Anita Patel, vice president of Pharmacy Services Development at Walgreens.
The index tracks flu cases based on prescription data from the company's pharmacies nationwide and is updated each Tuesday.
It also shows the regions of the country with the highest flu activity - Oklahoma, Mississippi, Tennessee, Arkansas and Texas.
The flu over the past month is "significantly higher" than the same period last year.
The Centers for Disease Control and Prevention estimates that there have been at least 24 million illnesses, 310,000 hospitalizations and 13,000 deaths so far this 2024-2025 flu season.
The CDC said flu cases are very high in a number of southern states, including Louisiana, Mississippi, Alabama, Georgia, Tennessee, North Carolina and Virginia.
States with low or minimal activity include Montana, West Virginia, Alaska and Hawaii.
"To protect yourself and others, I encourage everyone to get vaccinated, wash your hands frequently and if you're feeling symptoms, get tested right away," Patel said.
