Originally published by our sister publication Infectious Disease Special Edition
This article was updated on Jan. 6 to reflect the latest numbers.
By Ethan Covey
Flu activity, which has been low across the country since the end of the 2023-2024 flu season, began to slowly rise in late October, with larger increases the past few weeks, according to the CDC’s FluView influenza surveillance report for the week ending Dec. 28, 2024.
“Influenza-like illness activity has been above the national baseline for [several] consecutive weeks and is above baseline in seven of 10 HHS [Department of Health and Human Services] regions, and the percentage of positive flu tests from clinical health labs is also steadily increasing,” said Jasmine Reed, a CDC spokesperson, in early December. “Activity is expected to continue increasing for several weeks and remain elevated for weeks or months.”
Data from the week 52 FluView report shows a 18.7% increase in positive clinical lab results for influenza, up from 5.1% in week 48, and a 6.8% increase in visits to a healthcare professional for respiratory illness compared with the week ending Dec. 7 (3.4%). The cumulative hospitalization rate for influenza was 13.2 per 100,000 people.
The viruses co-circulating during the week ending Dec. 21 were influenza A(H1N1)pdm09, A(H3N2) and B viruses. Across the United States, flu activity is moderate in six jurisdictions, and high or very high in 42 jurisdictions, a significant move to the more severe category, which only had six jurisdictions reporting severe disease by Dec. 7.
Ms. Reed noted that it is not possible to predict how severe this season will be compared with the previous flu season.
“CDC publishes in season flu severity assessments each week at 2024-2025 United States Flu Season: Preliminary In-Season Severity Assessment | Influenza (Flu) | CDC during the flu season,” she said.
Regarding timing, the increases in flu activity that are seen are happening slightly later in the season than those from the 2023-2024 flu season and several weeks later than the 2022-2023 flu season. Those seasons peaked in late December and early December, respectively.
“While no two flu seasons are the same, the increases in flu activity we are currently seeing are within the range seen during past seasons in terms of timing,” Ms. Reed said. “How long activity will last and when the season will peak, however, cannot be predicted.”
She also stressed the importance of receiving a seasonal influenza vaccine, particularly with the arrival of the holiday season.
“CDC recommends everyone 6 months and older get an annual flu vaccine each year, and there is still time to get vaccinated this season,” she said. “With activity just beginning to pick up, there is still time to get vaccinated and protect yourself from flu before it starts spreading at elevated levels in your community.”
Between the passing holidays and its large gatherings, travel, and spending more times indoors, the virus will continue to spread, she explained. “A flu vaccine is the best tool to keep yourself and your family protected against flu as you spend time together this holiday season. Flu vaccination is especially important to help protect members of the family at higher risk of severe flu illness, like older adults, young children and people with certain chronic health conditions, like heart disease or diabetes.”
Ms. Reed reported no relevant financial disclosures.