Flu season is now in flu swing.
"'A lot of flu out there,'" Carrie Reed, PhD, spokesperson for the Centers for Disease Control and Prevention (CDC), noted to the Associated Press in early January.
In the United States, flu activity typically starts to increase in October, peaks between December and February, and then begins to decline through April and even May. Flu viruses tend to thrive in the cold, dry conditions of winter. The decrease in temperatures may also affect bacteria-fighting cells in the nose, reducing the power of our immune system to fight the flu and colds.
But in recent years, the usual flu season patterns have been disrupted by the COVID-19 pandemic. The 2020–2021 flu season was unusually mild, likely due to widespread mask-wearing, remote work and school, and social distancing. Flu activity patterns in 2021–2022 and 2022–2023 began to look more like those before the spread of COVID, although the 2022–2023 flu season was considered to be moderately severe. Last flu season, 2023–2024, was also moderately severe, with the timing and intensity of flu activity similar to pre-COVID flu seasons of the past.
With COVID and respiratory syncytial virus (RSV) also in circulation with flu, protecting your health during the fall and winter has become more challenging.
Now that we are into the winter months, what respiratory disease trends are we seeing over the 2024–2025 flu season?
Early forecasts for respiratory viruses this season
In August, the Centers for Disease Control and Prevention (CDC) released a report on their initial outlook for the current respiratory virus season, looking at the potential impact that flu, COVID and RSV may have on public health.
This combined report shows that the CDC anticipated similar or fewer total hospitalizations due to these three viruses compared to the previous season. In a late October update, the CDC continued to uphold their earlier assessment, noting that overall respiratory virus activity remained low at that time.
As of early January, flu, COVID and RSV have increased across the country, with RSV activity considered to be especially high—especially in young children.
How predictions for the flu season are turning out in early 2025
Looking specifically at flu activity, as of late December, flu cases have risen quickly since early December across the country since the fall; rates are well above the national baseline.
So far, the pattern of flu cases is mimicking the pattern observed in the 2019–2020 flu season, when cases rapidly increased at the beginning of December. That season saw three peaks in flu cases, occurring in early January, mid-February, and late March. It is too early to tell whether there will be multiple peaks this season.
This season, children aged from 0 to 4 years have been most affected by the flu, followed in order by people aged 5 to 24 years; adults aged 25 to 49 years; adults aged 50 to 64 years; and finally, adults aged 65 and older. Conversely, data collected by networks that track flu-related hospitalizations has shown that hospitalization rates have been highest in older adults with the flu.
The CDC has noted that its outlook reports on respiratory virus season have been based on historical data, modeling of different scenarios and consultations with experts. Ultimately, the impact of the current flu season will depend on the predominant flu strains that circulate, as well as the immunity that people have to the flu virus subtypes in circulation and the effectiveness of flu vaccines against those subtypes. Flu vaccines for the 2024–2025 flu season have been updated to match the viruses that are expected to circulate.
“[T]here are a lot of assumptions that go into a projection,” noted CDC Director Mandy Cohen, M.D., M.P.H., at an August press conference. “Say, for example, the number of people who ultimately get vaccinated against flu, COVID, and RSV is lower than expected—then that could mean more hospitalizations, not fewer.”
Unfortunately, flu vaccination rates across most groups of people have declined since the spread of COVID-19 in 2020. As of late December, rates in adults and pregnant women are similar to those recorded at the same time last flu season. Vaccination rates in children are lower than last season.
The bottom line: There's still time to get a flu shot
Although healthcare experts recommend getting a seasonal flu shot before the end of October, it's not too late to get your flu shot; as long as flu is circulating, vaccination provides protection. It generally takes about two weeks to build up sufficient flu antibodies. If you have questions about flu vaccination, talk to your doctor or pharmacist about it.
While the flu season may be similar to or milder than last season's, flu can be a serious threat to your health. Getting a seasonal flu vaccination every year is the best way to prevent flu and its potentially severe complications. Besides getting vaccinated, even everyday actions can make a difference in helping to protect you against flu and other respiratory viruses. These actions include simple things such as avoiding close contact with sick people, staying at home when you’re sick, covering coughs or sneezes, and washing your hands often.
Most people who get the flu will not need medical care or antiviral medication. However, if you develop symptoms of the flu and are at higher risk for serious complications from the flu—or if you become very sick or concerned about your symptoms—call your healthcare provider.
