RSV typically starts out looking exactly like a common cold: runny nose, coughing, sneezing, and sometimes a mild fever. In most older children and adults, that’s all it ever is. The reason people search for RSV specifically is usually because they’re worried about a baby, an elderly family member, or themselves getting worse rather than better. Since RSV symptoms overlap heavily with the flu, COVID-19, and ordinary colds, the only way to confirm it is through a test, but there are patterns and warning signs worth knowing.
Early Symptoms in Adults and Older Kids
When adults and school-age children catch RSV, the illness is mild enough that most never realize it isn’t just a cold. Expect a stuffy or runny nose, a dry cough, a low-grade fever, a sore throat, and general fatigue. These symptoms usually appear two to eight days after exposure, since RSV has a relatively short incubation period. You’re contagious for about three to eight days, and you can actually start spreading the virus a day or two before symptoms appear.
For healthy adults, the infection stays in the upper airways and clears on its own. But RSV can trigger flare-ups of asthma, COPD, or heart failure in people who already have those conditions. It can also progress to pneumonia in older adults or anyone with a weakened immune system. If a cough that seemed mild at first starts coming with shortness of breath or chest tightness after several days, that’s a sign the infection may have moved deeper into the lungs.
How RSV Looks Different in Babies
Babies under one year old are the group most at risk, and RSV is the leading cause of infant hospitalization in the United States. An infant’s airways are tiny, and RSV triggers inflammation and thick mucus production in the smallest branches of the lungs (the bronchioles). The immune response to the virus, more than the virus itself, causes swelling that can partially block those narrow passages and trap air.
The illness often starts the same way it does in adults: a runny nose, mild cough, and maybe a slight fever. But around day three to five, some babies take a turn. About 44% of symptomatic infants develop a lower respiratory tract infection, meaning the virus has moved beyond the nose and throat into the lungs. That’s when you’ll notice the signs that separate RSV from an ordinary cold.
Warning Signs That Need Immediate Attention
In infants and young children, the clearest signals of trouble are visible changes in how they breathe. These are the specific things to watch for:
- Retractions: The skin pulls inward just below the neck or under the breastbone with each breath. The child’s body is working harder than normal to pull air into the lungs.
- Nasal flaring: The nostrils visibly spread open with each inhale.
- Grunting: A short grunting sound at the end of each exhale. This is the body’s attempt to keep the lungs inflated and open.
- Head bobbing: The baby’s head bobs forward with each breath, a sign of significant effort.
- Fast or labored breathing: Noticeably rapid breathing, especially at rest or during feeding.
- Color changes: A bluish tint around the lips or fingertips signals low oxygen.
Beyond breathing, pay attention to feeding and behavior. A baby who is suddenly refusing to eat, producing far fewer wet diapers than usual, or becoming unusually irritable or limp and lethargic needs to be seen right away. These signs point to dehydration or oxygen levels that aren’t recovering on their own.
Why You Can’t Tell RSV Apart From Other Viruses by Symptoms Alone
RSV, the flu, and COVID-19 all share the same core symptoms: fever, cough, and sometimes shortness of breath. There’s no single symptom that reliably points to one virus over the others. Loss of taste and smell became associated with COVID-19 early in the pandemic, but that’s less consistent with newer variants. High fever with sudden body aches leans toward flu. Wheezing in a baby under one leans toward RSV. But none of these are definitive.
The practical answer is testing. Clinics and emergency departments commonly use rapid antigen tests that can check for RSV, flu, and COVID-19 from a single nasal swab. For RSV specifically, these rapid tests catch about 79% of true cases in children, with essentially no false positives. A more sensitive option is a PCR test (the same type widely used during the COVID-19 pandemic), which picks up roughly 87% of RSV cases and is better at detecting lower levels of virus. If a rapid test comes back negative but symptoms are concerning, a PCR test can provide a more reliable answer.
What RSV Season Looks Like
RSV circulates most heavily from fall through spring in temperate climates, though the exact timing shifts year to year. If your child develops cold symptoms during these months, RSV is one of the most likely culprits. Outside of RSV season, the same symptoms are more likely to be caused by rhinovirus, parainfluenza, or other common respiratory viruses. Knowing the season doesn’t confirm anything, but it raises or lowers the odds enough to be useful context when deciding whether to get tested.
How Long RSV Lasts
Most people recover from RSV within one to two weeks. The worst symptoms in babies, particularly the wheezing and breathing difficulty, tend to peak around day four or five of the illness and then gradually improve. The cough can linger for weeks even after the infection has cleared.
One important detail: while most people stop being contagious within about a week, infants and people with weakened immune systems can continue shedding the virus for four weeks or longer, even after they look and feel better. This matters for protecting other vulnerable people in the household.
Protection for High-Risk Infants
Preventive options now exist for the babies most vulnerable to severe RSV. A long-acting antibody treatment is recommended for all infants under eight months entering their first RSV season, unless their mother received an RSV vaccine during pregnancy at least 14 days before delivery. For babies aged 8 to 19 months entering a second RSV season, the antibody is recommended only for those at higher risk: children with chronic lung disease, severe immune deficiency, cystic fibrosis with significant lung involvement, or American Indian and Alaska Native children.
For pregnant women, an RSV vaccine given during pregnancy can pass protective antibodies to the baby before birth, often making the infant antibody treatment unnecessary. Most families will use one approach or the other, not both.