RSV (respiratory syncytial virus) causes symptoms that look a lot like a common cold, which makes it hard to identify on your own. A runny nose, cough, low fever, and fatigue are the hallmarks in both adults and children. What sets RSV apart is how it progresses, especially in young children: it often moves from mild upper respiratory symptoms into wheezing and labored breathing within a few days. The only way to confirm RSV definitively is with a diagnostic test, but understanding the symptom pattern can help you recognize when something more than a cold is going on.
RSV Symptoms in Adults
In most adults, RSV feels like a standard upper respiratory infection. You’ll likely notice a runny nose, sore throat, cough, headache, fatigue, and possibly a low-grade fever. These symptoms typically resolve in one to two weeks without treatment. Many adults with RSV never realize they have it because the illness is so similar to a cold.
The picture changes for adults over 50, especially those with underlying health conditions. RSV can progress to pneumonia or trigger flare-ups of asthma, COPD, or heart failure. If you’re in that age range and a “cold” lingers past two weeks, gets worse instead of better, or comes with shortness of breath or chest tightness, that’s worth a call to your doctor.
RSV Symptoms in Infants and Young Children
RSV follows a more recognizable pattern in babies and toddlers. It usually starts with a runny nose and decreased appetite before any other symptoms appear. One to three days later, a cough develops. Sneezing, fever, and wheezing often follow soon after. In older kids, this may look and feel like a regular cold. In infants, it can escalate quickly.
Very young babies, particularly those under six months, may show less obvious signs: irritability, decreased activity, poor feeding, and pauses in breathing lasting longer than 10 seconds. They may not develop a classic cough or fever at all, which can make RSV easy to miss early on.
Physical signs of breathing difficulty are the most important things to watch for. If your child’s nostrils flare with each breath, their chest appears to pull inward between or below the ribs, their breathing is noticeably fast, or they seem to be working hard to get air, those are signals that the infection has moved into the lower airways. Difficulty drinking fluids or worsening symptoms after initial improvement also warrant medical attention.
How RSV Differs From the Flu and COVID-19
Here’s the frustrating truth: RSV, the flu, COVID-19, and the common cold share overlapping symptoms like fever, cough, and sometimes shortness of breath. No single symptom reliably separates them. A few general patterns can offer clues, though they’re not definitive.
- RSV tends to produce more prominent wheezing, especially in children. It usually starts with a runny nose and builds gradually over several days.
- Influenza typically hits harder and faster, with sudden onset of high fever, body aches, and extreme fatigue.
- COVID-19 is more likely to cause loss of taste or smell (though this has become less common with newer variants) and can involve gastrointestinal symptoms.
- Common colds generally stay mild and don’t progress to wheezing or significant breathing trouble.
Because the overlap is so significant, a diagnostic test is the only reliable way to tell these infections apart.
How RSV Is Diagnosed
Two main types of tests detect RSV. PCR-based tests (sometimes called molecular or nucleic acid tests) are highly sensitive and are the gold standard. They’re processed in a lab and may take a few hours to a day for results. Rapid antigen tests provide quicker results but are less sensitive, meaning they can miss some infections, particularly in adults who tend to carry lower amounts of the virus.
If you visit a doctor or urgent care, they’ll typically swab your nose. Many clinics now use multiplex panels that test for RSV, flu, and COVID-19 simultaneously. Your doctor is more likely to order testing if you’re in a high-risk group, if a child is showing signs of lower respiratory involvement, or during RSV season (generally fall through early spring).
At-Home Testing
You can now test for RSV at home. The FDA has cleared a 4-in-1 home test (Flowflex Plus by Acon Laboratories) that detects RSV, influenza A, influenza B, and COVID-19 from a single nasal swab. It’s available at major retailers like CVS, Walgreens, and Albertsons, and can be used on children as young as six months when an adult administers the swab with the included nasal guard. Keep in mind that rapid home tests are generally less sensitive than lab-based PCR, so a negative result doesn’t completely rule out infection if symptoms are present.
Incubation Period and Contagiousness
After exposure to RSV, symptoms typically appear within four to six days. You can start spreading the virus a day or two before symptoms show up, and you remain contagious for about three to eight days after symptoms begin. Infants and people with weakened immune systems can shed the virus for four weeks or longer, even after they feel better. This is one reason RSV spreads so effectively through daycares and nursing homes.
Who Is at Highest Risk
Most healthy older children and adults handle RSV without complications. The groups that face serious risk include:
- Infants under 6 months, whose small airways are easily obstructed by inflammation and mucus
- Premature babies and children with congenital heart or lung conditions
- Adults 50 and older with chronic conditions like COPD, asthma, heart failure, diabetes with organ damage, chronic kidney or liver disease, severe obesity (BMI of 40 or higher), sickle cell disease, or weakened immune systems
- Adults 75 and older, regardless of underlying health
- Nursing home residents
For these groups, what starts as a cold can progress to pneumonia or bronchiolitis (inflammation of the small airways in the lungs), sometimes requiring hospitalization.
RSV Vaccination
A single-dose RSV vaccine is now recommended for all adults 75 and older and for adults ages 50 to 74 who have increased risk due to the conditions listed above. Three vaccines are available for this age group (made by GSK, Moderna, and Pfizer), with no preference for one over another. This is not an annual shot. If you’ve already received one dose, you’re considered fully vaccinated for now.
For infants, protection comes through a different route: either a maternal vaccine given during pregnancy or a preventive antibody given to the baby after birth. If your child is under 8 months heading into their first RSV season, or under 19 months with certain risk factors, ask your pediatrician about these options.