Several respiratory viruses are circulating right now, with influenza and RSV leading the pack. As of mid-April 2026, CDC surveillance data shows influenza testing at 4.7% positivity, RSV at 4.3%, and COVID-19 at 1.3%. Depending on your symptoms, any of these could be what you or the people around you are dealing with. Here’s how to tell them apart and what to expect.
Flu Is the Most Common Culprit
Influenza is currently the most frequently detected respiratory virus in clinical testing. The 2024-25 season saw nearly 490,000 positive flu tests out of about 4 million specimens, a positivity rate of 12.3% at its peak. Two strains of influenza A circulated almost equally this season: H1N1 accounted for 53.1% of subtyped samples and H3N2 for 46.9%. A smaller share, about 11%, were influenza B viruses, all from the Victoria lineage.
Flu hits fast. You’ll typically feel fine one day and miserable the next, with symptoms showing up one to four days after exposure. The classic picture is a sudden fever, body aches, chills, headache, sore throat, and a dry cough. Most people recover in three to seven days, though fatigue can linger. The rapid onset and intense body aches are what distinguish flu from a common cold, which builds more gradually.
RSV Is Not Just a Kids’ Illness
RSV, or respiratory syncytial virus, is running close behind influenza at 4.3% positivity. While most people associate RSV with babies and toddlers, it causes significant illness in older adults too. Symptoms look a lot like a bad cold: runny nose, coughing, sneezing, fever, and sometimes wheezing. The incubation period is four to six days, slightly longer than the flu. Most infections last three to seven days, but coughing and congestion can hang on for weeks.
RSV becomes more dangerous at the extremes of age. In infants, it can cause bronchiolitis, where the small airways in the lungs become inflamed and clogged with mucus. In adults 65 and older, it can progress to pneumonia. If you notice labored breathing, a bluish tint to the lips, or a very high fever in a baby or elderly family member, that warrants urgent medical attention.
COVID-19 Is Still Circulating, Just Quieter
COVID-19 positivity has dropped to 1.3%, making it the least prevalent of the three major respiratory viruses right now. The dominant variants over the past year have been descendants of the JN.1 lineage, including KP.2 and related subvariants that share a common set of mutations. The symptoms haven’t changed meaningfully from what most people experienced in previous waves: sore throat, congestion, cough, fatigue, headache, and sometimes fever.
Cases generally feel milder now, but that’s largely because most people carry immunity from prior infections, vaccination, or both, not because the virus itself has weakened. COVID’s incubation period ranges from 2 to 14 days, though most people develop symptoms within three to five days of exposure. A typical case lasts three to seven days, but some people experience lingering symptoms for weeks or longer.
Norovirus: The “Stomach Bug”
If what’s going around your household or workplace involves vomiting and diarrhea rather than cough and congestion, norovirus is the likely explanation. The 2025-26 norovirus season has seen 907 outbreaks reported through early March 2026 across 14 participating states, which falls within the normal historical range. It’s not an unusual surge, but norovirus is extremely contagious and tends to tear through schools, cruise ships, and nursing homes in waves.
Norovirus comes on suddenly, usually 12 to 48 hours after exposure. Expect intense nausea, vomiting, watery diarrhea, and stomach cramps. Some people get a low-grade fever. The worst of it passes in one to three days, but you remain contagious for at least 48 hours after symptoms stop. There’s no antiviral for norovirus. Staying hydrated is the priority, especially for young children and older adults who can become dehydrated quickly.
“Walking Pneumonia” in Young Children
One pattern worth knowing about: infections caused by Mycoplasma pneumoniae, sometimes called walking pneumonia, surged through 2024 and are still elevated in some parts of the country. What made this wave unusual was the age group it hit hardest. Mycoplasma infections have traditionally been a school-age and adolescent illness, but the 2024 surge affected children ages two to four and even infants at higher rates than expected. The CDC linked this to the lower baseline of Mycoplasma activity during the pandemic years, which left younger children without the typical immune exposure.
Walking pneumonia causes a persistent, often worsening cough that can last for weeks, along with low-grade fever, fatigue, and sometimes a headache. It’s called “walking” pneumonia because people generally don’t feel sick enough to stay in bed, even though the infection is in their lungs. It responds well to antibiotics, unlike viral respiratory infections. If your child has had a cough that won’t quit for more than a week or two, this is worth asking about.
Bird Flu: Low Risk but on the Radar
You may have seen headlines about H5N1 bird flu. While human cases in the United States have occurred, they’ve been linked to direct contact with infected animals, particularly among poultry and dairy farm workers. There is no established human-to-human transmission. Most U.S. cases have been mild, with eye redness being the most common symptom. Some infected individuals reported no symptoms at all. More serious cases can involve high fever, shortness of breath, and pneumonia, but this remains rare.
For the general public, bird flu is not what’s making you sick right now. It’s worth monitoring, but it’s not circulating in the community the way influenza, RSV, and COVID-19 are.
How to Tell What You Have
Symptom overlap between these viruses is real, and no checklist is perfect. But some patterns help narrow things down:
- Sudden high fever with body aches: Most likely influenza.
- Congestion and wheezing, especially in young children or older adults: Think RSV.
- Sore throat and fatigue with mild or no fever: Could be COVID-19 or a common cold.
- Vomiting and diarrhea with little or no respiratory symptoms: Probably norovirus.
- Lingering cough that worsens over days to weeks: Consider Mycoplasma pneumoniae, especially in children.
Home rapid tests can confirm COVID-19 and, in some kits, influenza. If you want a definitive answer, many clinics offer multiplex tests that check for flu, COVID, and RSV from a single nasal swab.
When to Return to Normal Activities
The CDC simplified its guidance for all respiratory viruses into a single recommendation: you can return to normal activities once your symptoms have been improving for at least 24 hours and any fever has been gone for a full day without fever-reducing medication. This applies to flu, COVID-19, and RSV alike. For norovirus, the standard is waiting at least 48 hours after vomiting and diarrhea stop before preparing food or being around vulnerable people.
Vaccines That Cover the Big Three
Updated vaccines exist for all three major respiratory viruses. The CDC recommends annual flu and COVID-19 vaccines for everyone six months and older, ideally in September or October before respiratory season peaks between December and March. You can get both at the same visit.
RSV vaccines are recommended for adults 75 and older, adults 60 to 74 with increased risk, and for protecting infants either through maternal vaccination during the third trimester of pregnancy or through an antibody given to the baby at birth. If you received an RSV vaccine last year, you don’t need another dose. There is no vaccine for norovirus.