Multiple respiratory viruses are circulating at the same time right now, which is why it feels like everyone around you is sick. CDC surveillance data for the week ending February 21, 2026, shows influenza testing at 17.9% positive, RSV at 8.6%, and COVID-19 at 4.3%. When all three viruses peak during the same stretch of winter, the combined effect hits workplaces, schools, and families hard.
Three Viruses Circulating at Once
This isn’t just one illness making the rounds. Influenza, RSV, and COVID-19 are all spreading simultaneously, and their seasons overlap heavily during the coldest months. Flu is currently the dominant driver, with nearly 1 in 5 tests coming back positive. RSV, which hits young children and older adults especially hard, is close behind. COVID-19 positivity is lower than in past winters but still contributing to the overall wave of illness.
COVID-19 itself is now split across several viral lineages. The XFG family of variants makes up the largest share of circulating virus, with the original XFG strain accounting for about 29% of sequenced cases. NB.1.8.1 follows at 21%, with XFG.2.5.1 at 16%. The rest is a patchwork of smaller lineages. This kind of viral diversity means your immune system may not recognize the newest version as well as the last one you encountered, even if you’ve been sick or vaccinated before.
Why Winter Makes It Worse
Cold weather doesn’t directly make you sick, but it creates the perfect conditions for viruses to spread. The biggest factor is indoor humidity. During winter, heated indoor air often drops below 40% relative humidity, and that dry air changes how viral particles behave. Research from classroom settings found that when humidity falls below 40%, viable virus particles can travel up to 18 feet from the source within 15 minutes. Raising humidity above 40% significantly reduced the number of infectious particles detected at every distance tested.
Dry air does two things at once: it lets respiratory droplets shrink and float farther, and it helps many enveloped viruses (including influenza and the virus that causes COVID-19) survive longer on those droplets. The sweet spot for reducing transmission appears to be 40% to 60% relative humidity. Most homes and offices in winter sit well below that range, which is one reason respiratory illnesses cluster so reliably in January and February.
On top of that, people spend far more time indoors during cold months, often in poorly ventilated rooms with windows sealed shut. More people sharing the same stale air means more opportunities for any circulating virus to jump from person to person.
Immunity Isn’t What It Used To Be
By now, most people have some combination of past infections and vaccinations working in their favor, a concept researchers call hybrid immunity. Studies show this combined protection can last at least a year for COVID-19, with effectiveness against severe illness holding at around 97% at the 12-month mark. But protection against getting infected at all fades faster, especially as new variants drift away from the versions your immune system learned to recognize.
The bigger issue is that very few people are keeping their immunity current. Only about 17.5% of adults have received the 2025-26 COVID-19 vaccine, and that number drops to just 8.8% for children. Flu vaccine uptake is better but still leaves roughly half the population unvaccinated: about 46.5% of adults and 47.5% of children have gotten a flu shot this season. Among adults 65 and older, coverage is higher (69% for flu, 33.5% for the updated COVID vaccine), but even in that group, the majority haven’t received the latest COVID shot. When most of the population is running on older immunity, viruses find plenty of susceptible hosts.
Telling These Viruses Apart
One reason this wave of illness feels so overwhelming is that COVID-19, flu, and RSV look almost identical in the first few days. All three can cause fever, chills, cough, sore throat, congestion, body aches, headache, and fatigue. The overlap is nearly complete, which makes it impossible to tell them apart based on symptoms alone.
A few subtle differences exist. Loss of taste or smell still leans more toward COVID-19 than flu, though it’s become less common with newer variants. Diarrhea and vomiting show up more often in children with flu, while COVID-19 can cause GI symptoms at any age. RSV tends to produce heavier congestion and wheezing, particularly in babies and toddlers, though in adults it often just feels like a bad cold. The only reliable way to know which virus you’re dealing with is a test. Many pharmacies now carry combination tests that check for all three at once.
What Actually Helps Right Now
The single most effective thing you can do in your own space is manage your air. If you have a humidifier, keep indoor humidity between 40% and 60%. That one change meaningfully reduces how far and how long respiratory viruses remain infectious indoors. A portable HEPA air purifier adds another layer of protection. Lab testing on HEPA filters showed they captured over 85% of infectious virus particles within 5 minutes, over 96% within 10 minutes, and more than 99.97% given enough runtime. In a bedroom or home office, a properly sized HEPA unit can dramatically cut your exposure.
Ventilation matters too. Opening a window even a few inches introduces fresh air that dilutes viral particles. If it’s too cold for that, running a bathroom exhaust fan or kitchen hood helps move air through the space. The goal is to avoid sitting in a sealed room with recirculated air for hours.
Getting vaccinated still reduces your chances of severe illness, even if it won’t make you bulletproof against infection. Given that most people haven’t gotten this season’s updated shots, there’s a large gap between available protection and actual protection in the population. If you haven’t been vaccinated this season and you’re in a higher-risk group, the window is still open. Staying home when you’re symptomatic, washing hands frequently, and wearing a mask in crowded indoor spaces during peak weeks all chip away at transmission in practical, measurable ways.