As of late February 2026, the main viruses circulating in the United States are influenza (flu), COVID-19, and RSV (respiratory syncytial virus). Flu is currently the most active of the three, with a test positivity rate of 17.9%, followed by RSV at 8.6% and COVID-19 at 4.3% for the week ending February 21. Norovirus, the so-called “stomach flu,” is also circulating at typical seasonal levels.
Influenza Is the Dominant Virus Right Now
Flu is driving the bulk of respiratory illness this season. A positivity rate near 18% means roughly one in five people tested for respiratory viruses is coming back positive for influenza. Symptoms typically appear one to four days after exposure and include sudden fever, body aches, chills, fatigue, cough, and sore throat. Most healthy adults recover within one to two weeks, though the fatigue can linger longer.
Annual flu vaccination is recommended for everyone aged six months and older. If you haven’t gotten your flu shot this season, it can still offer protection, especially while activity remains high.
COVID-19 Is Circulating at Lower Levels
COVID-19 positivity currently sits at 4.3%, well below its winter peaks in previous years. The virus continues to evolve, though. The dominant lineage right now is XFG, which along with its sub-lineages (XFG.2.5.1, XFG.1.1, XFG.14.1, and XFG.6) accounts for roughly 60% of all sequenced cases. Another lineage called NB.1.8.1 makes up about 21%.
The most common COVID symptoms have shifted since the early pandemic years. Right now, the typical presentation is a runny or stuffy nose, headache, and sore throat. Symptoms can start anywhere from two to 14 days after exposure, though most people notice them within three to five days. If you’re unsure whether you have the flu or COVID, a rapid test or PCR test can tell the difference, and the distinction matters because treatment options differ.
RSV Remains Active, Especially for Young Children
RSV positivity is at 8.6%, making it a significant contributor to respiratory illness this season. In most adults and older children, RSV feels like a bad cold: congestion, cough, mild fever, and general fatigue. It becomes more serious in infants under one year old and adults over 65, where it can lead to lower respiratory infections like bronchiolitis or pneumonia that require hospitalization.
For infants under eight months entering their first RSV season who were not protected by maternal vaccination during pregnancy, a preventive antibody treatment (clesrovimab) is recommended. Adults aged 50 to 59 with conditions that put them at higher risk for severe RSV are also eligible for an RSV vaccine. Unlike the flu shot, RSV vaccination is currently a one-time dose rather than an annual booster.
Norovirus Is Also Making the Rounds
Norovirus, the most common cause of stomach bugs, is circulating at levels within the normal range for this time of year. Between August 2025 and early February 2026, participating states reported 644 outbreaks to the CDC, compared to 1,707 during the same window last season. So while norovirus is present, this is not an unusually bad year for it.
Norovirus symptoms are distinct from respiratory viruses: sudden onset of vomiting, diarrhea, nausea, and stomach cramps, usually lasting one to three days. It spreads extremely easily through contaminated food, surfaces, and close contact with someone who’s sick. Thorough handwashing with soap and water is the best prevention, as alcohol-based hand sanitizers are less effective against norovirus.
How to Tell Which Virus You Have
There’s significant overlap in respiratory virus symptoms, which makes it hard to tell flu, COVID, and RSV apart based on how you feel. All three can cause congestion, cough, sore throat, and fatigue. A few patterns can help narrow it down. Flu tends to hit hard and fast, with prominent body aches and high fever. COVID is more likely to start with a runny nose, headache, and sore throat that builds gradually. RSV in adults usually looks like a lingering cold with heavy congestion. But the only reliable way to know is testing, and combination tests that check for all three viruses at once are widely available at pharmacies and clinics.
Stomach symptoms like vomiting and diarrhea point strongly toward norovirus rather than a respiratory virus, though COVID occasionally causes mild GI symptoms too.
What to Do if You Get Sick
The CDC’s current guidance applies to all respiratory viruses equally. If you develop symptoms, stay home and away from others, including household members who aren’t sick. You can return to normal activities once both of these have been true for at least 24 hours: your symptoms are improving overall, and you’ve had no fever without the help of fever-reducing medication.
After you return to your routine, take extra precautions for the next five days. That includes wearing a well-fitting mask around others indoors, improving ventilation when possible, keeping your distance from people at higher risk, and practicing good hand hygiene. If you tested positive for a respiratory virus but never developed symptoms, the same five-day precaution window applies from the date of your positive test.
For norovirus, the approach is simpler: stay home until at least 48 hours after symptoms stop, and be meticulous about handwashing and disinfecting surfaces with bleach-based cleaners.