As of late February 2026, respiratory illness activity in the United States is at a moderate level overall, with influenza driving the most healthcare visits. COVID-19 and RSV are also circulating, and whooping cough cases remain elevated above pre-pandemic levels. Here’s what’s spreading, how to tell these illnesses apart, and what you can do about it.
Influenza Is the Biggest Driver Right Now
Flu is responsible for the largest share of respiratory illness this season. About 3.2% of all outpatient healthcare visits in the U.S. are currently for influenza, making it the dominant circulating virus. Clinical laboratory data from the most recent surveillance week show a 17.9% positivity rate among flu tests, with over 15,000 positive specimens reported in a single week.
What’s unusual this season is the mix of flu types. Influenza B is actually edging out Influenza A in recent weeks, accounting for 55% of positive tests compared to 45% for Influenza A. That said, Influenza A (H3N2) has been the most frequently reported type across the full season. Among H3N2 viruses genetically analyzed by the CDC, 92.4% belong to a single genetic group called subclade K. All of the Influenza B viruses tested belong to the Victoria lineage.
For most people, flu means a few days of fever, body aches, fatigue, and cough. Symptoms typically show up one to four days after exposure. Mississippi currently has high flu activity based on wastewater monitoring, but most states are seeing moderate levels.
COVID-19 Is Circulating at Low but Uneven Levels
COVID-19 accounts for about 0.6% of outpatient visits nationally, putting it well below flu in terms of people seeking care. But wastewater data tell a more nuanced story: Arizona, Oklahoma, and Washington all show very high levels of the virus in sewage, suggesting significant transmission in those areas even if fewer people are showing up at clinics.
The virus continues to evolve. The dominant variant family right now is XFG, which in various sub-lineages accounts for roughly 65% of all sequenced cases. The single largest lineage is XFG at 29%, followed by NB.1.8.1 at 21% and XFG.2.5.1 at 16%. Several other XFG offshoots make up smaller shares. This level of variant diversity is typical for this stage of the pandemic, and none of these lineages have been flagged as causing more severe illness than their predecessors.
COVID symptoms still overlap heavily with flu: fever, cough, sore throat, fatigue, and congestion. One distinguishing feature is that loss of taste or smell is more common with COVID than with flu, though it’s less frequent with newer variants than it was early in the pandemic. COVID also tends to have a slightly longer incubation period, with symptoms appearing two to five days after infection (and occasionally up to 14 days), compared to one to four days for flu.
RSV Hits Young Children and Older Adults Hardest
RSV (respiratory syncytial virus) is also at about 0.6% of outpatient visits nationally, similar to COVID. For most adults, RSV feels like a bad cold. But for two groups, it can be serious enough to require hospitalization.
Infants under 12 months are by far the most vulnerable. Hospitalization rates for this age group have reached roughly 1,100 per 100,000 over the current season. That means about 1 in 90 infants in this age group end up hospitalized for RSV. Children aged 12 to 23 months also face high rates, around 770 per 100,000. Adults 75 and older are the next most affected group, with hospitalization rates near 427 per 100,000.
In babies, RSV often starts with runny nose and decreased appetite before progressing to wheezing, rapid breathing, or difficulty breathing. If your infant is breathing fast, flaring their nostrils, or refusing to eat, those are signs to seek care promptly.
Whooping Cough Remains Elevated
Beyond the usual respiratory trio, whooping cough (pertussis) is worth knowing about. Cases surged dramatically in 2024, with more than six times as many reported cases compared to 2023. That spike peaked in November 2024 and has been trending down since, but case numbers in early 2025 still remain higher than pre-pandemic levels.
Whooping cough starts out looking like a regular cold, with mild cough and runny nose, before developing into intense coughing fits that can last for weeks. The coughing spells sometimes end with a distinctive “whoop” sound as the person gasps for air, though this is more common in children than adults. It’s particularly dangerous for infants under 12 months who haven’t completed their vaccine series. If you or your child has a cough that’s been worsening over two or more weeks, especially with vomiting after coughing fits, it’s worth getting tested.
How to Tell What You Have
The honest answer is that you often can’t tell from symptoms alone. The CDC is explicit on this point: flu and COVID share so many signs that testing is the only reliable way to distinguish them. Both cause fever, cough, fatigue, sore throat, body aches, and congestion. RSV in adults looks much the same.
A few patterns can offer clues, though. Flu tends to hit suddenly, with body aches and high fever arriving within hours. COVID more often builds gradually over a couple of days. Loss of taste or smell still points more toward COVID. A cough that gets progressively worse over weeks rather than improving suggests whooping cough rather than a viral infection.
Rapid home tests for both COVID and flu are widely available at pharmacies. If you’re in a high-risk group (over 65, pregnant, immunocompromised, or have chronic conditions like asthma or diabetes), testing early matters because antiviral treatments for both flu and COVID work best when started within the first day or two of symptoms.
Vaccines and Prevention for This Season
Annual flu vaccination is recommended for everyone 6 months and older, and it’s not too late to get one if you haven’t already. This season’s vaccine targets the circulating strains, including H3N2.
For RSV, there are now immunization options for the groups most at risk. Infants under 8 months who are born during or entering their first RSV season can receive a protective antibody injection (either nirsevimab or clesrovimab). Adults aged 50 to 59 with conditions that put them at higher risk for severe RSV can receive an RSV vaccine, and it’s also available for older adults. RSV vaccination is currently a one-time dose, so if you’ve already received one, you don’t need another.
Beyond vaccines, the basics still work. Washing your hands frequently, staying home when you’re sick, and improving ventilation in indoor spaces all reduce transmission of every respiratory virus circulating right now. If you’re caring for an infant during RSV season, hand hygiene before touching the baby and keeping sick visitors away are the most effective steps you can take.