The sudden appearance of this symptom could be your body's alarm bell going off, a top infectious disease MD explains.
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After last year’s brutal flu season—classified by the U.S. Centers for Disease Control and Prevention (CDC) as “high severity” and the most severe since 2017-2018—experts have a cautiously optimistic outlook for the 2025-2026 season.
“Back-to-back severe flu seasons are rare because people carry over some immunity from the previous year due to the high viral activity in the community,” says Suraj Saggar, MD, chief of infectious disease at Holy Name Medical Center in New Jersey. “Because last year was deemed a severe flu season in the Northern Hemisphere, the prediction is for a moderate flu season this year.”
The U.S. Centers for Disease Control and Prevention (CDC) announced that it expects the 2025-2026 flu season to be moderate across all ages. However, there’s a significant challenge this year: the federal government shutdown thwarted the CDC’s ability to continue publishing routine flu data from its public health partners. The agency’s FluView tracker—which normally provides weekly updates on flu activity across the country—was last updated September 26, a few days before the shutdown began. Though the shutdown is expected to end soon, it’s unclear how long it may take for the FluView tracker to update again.
Though Dr. Saggar says that flu activity is still low in the U.S, there’s typically a peak in January and February—”although that can depend on several factors, including weather—a milder fall may mean more people stay outdoors, giving the flu less time to circulate,” he explains. And, he adds, it is definitely not too late to get your flu shot if you haven’t yet.
So how do you know if you have the flu? Ahead, Dr. Saggar explains what you should be on the lookout for, what to do if you catch the flu, and how to best protect yourself from getting it in the first place.
What’s the main flu symptom in 2025?
The most distinctive characteristic of influenza this year? A rapid spike in body temperature. Unlike a cold, which develops gradually with a scratchy throat and mild congestion, flu symptoms can come on quickly, are more intense, and last longer, according to Dr. Saggar. Flu strains typically cause fevers between 102°F and 104°F, accompanied by severe chills that leave you alternating between freezing cold and burning up.
“Flu symptoms usually come on suddenly, and people who have flu often first feel fever or chills, followed by cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, and fatigue,” Dr. Saggar says. “You may feel rundown or exhausted even before the fever hits.” And that rapid-onset high fever serves as the body’s warning system that generally distinguishes the flu from Covid-19, RSV, and the common cold.
How long do fevers from the flu last?
Many patients sick with the flu report that their fevers last up to five to seven days, which means it’s crucial to monitor your temperature and stay hydrated throughout your illness, Dr. Saggar says.
“If you think you have the flu, it’s a good idea to go get tested because it helps us gather accurate data and also because we have antiviral treatments that can lessen the severity and duration by one to three days,” he says. And while that might not sound like much in the grand scheme of things, if you’ve ever had the flu then you well know that one day less of feeling miserable is well worth the trip to the pharmacy.
If your fever breaks but then returns, or if it persists beyond seven days, contact your doctor. A fever that returns after breaking or lasts more than seven days could signal a secondary bacterial infection or flu complications—something that’s especially concerning for high-risk populations, according to Dr. Saggar.
“What matters far more than the flu forecast is your personal risk profile,” he says. People at higher risk of developing serious flu-related complications include those 65 years and older, pregnant women, children younger than 5 years, and people of any age with certain chronic medical conditions such as asthma, diabetes, or heart disease, according to the CDC.
What does treatment look like?
If you develop a sudden high fever, there are steps you can take at home while monitoring your symptoms. Stay hydrated with water, herbal tea, or electrolyte drinks, as fever increases fluid loss through sweating. Use over-the-counter fever reducers such as acetaminophen or ibuprofen—if recommended by your doctor—and apply a cooling compress to help lower body temperature.
“Rest is essential—your body needs energy to fight the infection,” says Dr. Saggar. Stay home for at least 24 hours after your fever subsides without medication to avoid spreading the virus to others. People are contagious a day before symptoms start and up until their fever has resolved and symptoms are improving—as long as five to seven days after getting sick.
While most people recover from the flu within a week or two, certain symptoms warrant immediate medical attention. Dr. Saggar recommends seeking emergency medical care if you experience any of the following:
- Difficulty breathing or shortness of breath
- Persistent pain or pressure in the chest or abdomen
- Persistent dizziness, confusion or inability to arouse
- Seizures
- Severe muscle pain
- Severe weakness or unsteadiness
How to stay safe this flu season
While experts predict this flu season will be more moderate, there are a few key steps to keep in mind, including how to maximize your odds of staying healthy. As Dr. Sagger says, “The best defense remains prevention and having healthy habits overall. Get your annual flu shot if you haven’t already, wash your hands frequently, and stay home when you’re sick.”
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