Sick right now? Flu is resurging to yet a higher peak this season.

While H5N1 bird flu ratchets up anxiety and egg prices, seasonal influenza viruses are rallying to a second high this winter, an uncommon course not seen in most years. Flu cases had previously peaked this season at the very end of December. At week 52—ending on December 28—the percentage of outpatient visits related to influenza-like illnesses (ILI) hit about 6.76 percent, then ticked down the first week of 2025 (week 1). The percentage of ILI visits is the standard metric for tracking flu activity, which tends to peak at around 7 percent or lower in a given season. The 2009–2010 flu season—when the novel H1N1 (aka swine flu) emerged—stands out for hitting a decades' high of 7.7 very early in the season (week 42).

While ILI visits continued to decline in week 2 of this year, things took a turn in week 3. In the latest data for week 4—ending on January 25—the ILI visits are back up to about 6.95 percent. Few flu seasons have two peaks, particularly at such high intensities. A notable exception was the 2019–2020 flu season, which had three peaks: 7 percent at week 52, 6.8 percent at week 6, and 6.4 percent at week 12. After that, the COVID-19 pandemic hit, and influenza activity plummeted below baseline levels. The 2020–2021 flu season was essentially nonexistent, with ILI activity staying well below baseline for the entire season. Currently, flu activity is categorized as "very high" in 29 states, and "high" in 15. States in the South are ablaze with flu. Louisiana, Tennessee, and South Carolina are at the highest "very high" level. But parts of the Northeast corridor are also seeing extremely high activity, including Massachusetts, New Hampshire, New Jersey, and New York City.

As often is the case in flu seasons, the age group hardest hit this year are children ages 0 to 4. The CDC recorded 16 pediatric deaths linked to flu in week 4 of the season, bringing the season's total pediatric deaths to 47. Overall hospitalizations are up. The Centers for Disease Control and Prevention estimates that there have been at least 20 million illnesses, 250,000 hospitalizations, and 11,000 deaths from flu so far this season. About 44 percent of US adults have gotten their flu shot, far below the public health goal of 70 percent. Laboratory surveillance of influenza cases in week 4 indicates that nearly all of the cases are from influenza A viruses, about an even split between H1N1 and H3N2, which has been the case over the course of the season. Around 2 percent of cases were the influenza B Victoria lineage.