As of early March 2026, the main viruses circulating in adults are seasonal influenza, COVID-19, RSV, norovirus, and human metapneumovirus (HMPV). Influenza is the most active of the respiratory viruses right now, with 15.8% of tests coming back positive nationally. COVID-19 and RSV are also still in play but at lower levels. Here’s what each virus looks like, who’s most at risk, and what to watch for.
Influenza Is the Dominant Respiratory Virus
Flu activity remains elevated across the country, and influenza A(H3N2) is the strain driving the vast majority of cases. Of all flu viruses subtyped in public health labs this season, about 88% have been H3N2. Influenza B has been picking up more recently and now accounts for roughly 30% of positive specimens in the most recent week, so it’s worth knowing that both types are out there.
H3N2 strains tend to hit older adults especially hard. The highest hospitalization rate this flu season is among adults 65 and older, at 251.3 per 100,000 people. That’s more than triple the rate for adults aged 50 to 64 (67.2 per 100,000) and nearly nine times higher than the rate for adults 18 to 49 (29.8 per 100,000). Flu symptoms in adults typically come on fast: fever, body aches, chills, cough, and fatigue that can knock you out for a week or more.
Influenza A activity is declining in most parts of the country, but influenza B trends vary by region. If you haven’t been vaccinated this season, the flu shot still offers protection, particularly as B activity may not have peaked everywhere yet.
COVID-19 Is Declining but Still Present
COVID-19 is winding down nationally, with test positivity at 3.8% and the epidemic trend classified as declining. That said, several states still show high viral levels in wastewater monitoring, including Alabama, Delaware, Illinois, Maine, Minnesota, Mississippi, and Nebraska. If you’re in one of those areas, transmission may be more active than the national numbers suggest.
The variant landscape has shifted considerably. The XFG lineage and its sublineages now make up the largest share of circulating virus, with XFG itself at about 29% of sequenced cases. NB.1.8.1 accounts for roughly 21%, and XFG.2.5.1 follows at 16%. No single variant is overwhelmingly dominant, which means the virus is diversifying rather than being driven by one breakout strain.
COVID symptoms in adults continue to overlap heavily with other respiratory viruses: cough (often dry), sore throat, congestion, fatigue, and sometimes fever. Loss of taste or smell, once a hallmark early in the pandemic, is less commonly reported with newer variants. The updated 2024-2025 COVID vaccine is recommended for all adults, with an additional dose available for those 65 and older or anyone with moderate to severe immune compromise.
RSV Is Elevated and Climbing in Some Regions
RSV activity is elevated and increasing in parts of the country, with 9.1% of tests coming back positive. The epidemic trend nationally is holding steady rather than declining, which means RSV season isn’t over yet.
In most healthy adults, RSV looks and feels like a bad cold: runny nose, cough, mild fever, and general fatigue. But in adults over 65 or those with chronic lung or heart conditions, RSV can move into the lower airways and cause pneumonia or bronchiolitis. Warning signs of a more serious infection include wheezing, rapid or labored breathing, a preference for sitting upright rather than lying down, and in severe cases, a bluish tint to the lips or fingernails. RSV vaccines are now available for adults 60 and older and for pregnant individuals to protect newborns.
Norovirus Is Circulating at Typical Levels
Norovirus, the leading cause of vomiting and diarrhea outbreaks, is active this winter but not unusually so. Between August 2025 and early February 2026, participating states reported 644 outbreaks to the CDC’s NoroSTAT system. That’s well below the 1,707 outbreaks reported during the same window last season and falls within the normal historical range.
Norovirus spreads incredibly easily through contaminated food, surfaces, and close contact with someone who’s sick. Symptoms hit fast, usually 12 to 48 hours after exposure: sudden onset of vomiting, watery diarrhea, nausea, and stomach cramps. Most healthy adults recover in one to three days, but dehydration is the main risk, particularly for older adults. There’s no vaccine or antiviral for norovirus. Handwashing with soap and water (not just hand sanitizer) is the most effective way to prevent spread, since alcohol-based sanitizers don’t reliably kill it.
Human Metapneumovirus: The Virus Most People Haven’t Heard Of
HMPV circulates every winter and spring alongside the better-known respiratory viruses, and it accounts for roughly 3 to 5% of symptomatic respiratory infections in older and high-risk adults each season. It doesn’t grab headlines the way flu or COVID do, but it’s a real player. In one analysis spanning three consecutive flu seasons, HMPV was responsible for about 21% of respiratory illness cases that had a confirmed viral cause.
In healthy younger adults, HMPV usually causes mild cold-like symptoms and resolves on its own. In adults over 65, the picture can be more serious. Cough is the most common symptom, reported in over 90% of older adults with confirmed HMPV. Shortness of breath follows at around 87%, with wheezing at 73% and nasal congestion at 71%. Fever shows up in only about half of older adult cases, which can make it harder to recognize as something beyond a lingering cold.
For adults with weakened immune systems, HMPV is particularly concerning. These patients frequently report fatigue, worsening mucus production, and constitutional symptoms like chills and malaise on top of the respiratory issues. About 35% of HMPV infections in high-risk adults involve the lower respiratory tract, meaning pneumonia or bronchitis rather than just an upper airway cold. There’s currently no vaccine or specific antiviral treatment for HMPV, so management focuses on rest, fluids, and monitoring for worsening breathing.
How to Tell These Viruses Apart
Honestly, you often can’t based on symptoms alone. Flu tends to come on suddenly with high fever, severe body aches, and exhaustion. COVID more commonly starts with a sore throat and dry cough, and fever is less predictable. RSV and HMPV both lean toward cough, congestion, and wheezing, especially in older adults. Norovirus is the easy one to distinguish since it centers on the gut rather than the lungs.
If knowing the specific virus matters for your situation (because you’re older, immunocompromised, or live with someone who is), combination tests that check for COVID, flu, and RSV simultaneously are widely available at pharmacies and clinics. Identifying flu early is particularly useful because antiviral treatment works best when started within the first 48 hours of symptoms.
Protecting Yourself During Peak Season
The annual flu vaccine is recommended for all adults and remains the single most effective tool against influenza. The updated COVID vaccine for the 2024-2025 season targets currently circulating variants and is recommended for everyone six months and older. RSV vaccines are specifically targeted at adults 60 and older. Getting vaccinated even partway through the season still reduces your risk of severe illness and hospitalization.
Beyond vaccines, the basics still work. Wash your hands frequently, especially during norovirus season when hand sanitizer falls short. Stay home when you’re symptomatic to avoid spreading whatever you’ve picked up. And if you’re in a high-risk group, pay attention to regional trends. Wastewater data and CDC activity maps can tell you whether viral levels in your state are higher than the national picture suggests.