RSV, or respiratory syncytial virus, causes symptoms that look a lot like a common cold: runny nose, coughing, sneezing, fever, and congestion. Most infections clear up on their own in one to two weeks. But in infants, older adults, and people with weakened immune systems, RSV can move deeper into the lungs and become serious. Knowing which symptoms are routine and which signal trouble is the key to handling this virus.
Common RSV Symptoms
Symptoms typically show up 4 to 6 days after exposure. They appear in stages rather than hitting all at once, which is why RSV often starts out looking like a mild cold before revealing itself as something more significant. The usual lineup includes:
- Runny nose and congestion
- Coughing and sneezing
- Fever
- Wheezing
- Decreased appetite
For healthy older children and adults, that list is often the full extent of it. The illness runs its course in a week or two, and recovery happens at home with rest and fluids, much like any other upper respiratory infection.
How RSV Looks Different in Infants
Babies under 6 months old don’t always show the typical cold symptoms. Instead, you may notice irritability, decreased activity, and changes in breathing. A baby who suddenly seems less interested in feeding or is unusually fussy may be showing the earliest signs of RSV, even without an obvious runny nose or cough.
The biggest concern with RSV in infants is that the virus can move into the smaller airways of the lungs, causing bronchiolitis (inflammation of those tiny airways) or pneumonia. When that happens, breathing becomes visibly harder. You might see the skin between the ribs pulling inward with each breath, rapid breathing, or flaring nostrils. In very young infants, RSV can cause apnea, which means pauses in breathing lasting more than 10 seconds.
Difficulty breathing, refusal to drink fluids, or symptoms that are getting worse rather than better are all reasons to seek medical attention promptly. Because infants can’t tell you how they feel, watching their breathing pattern and feeding behavior gives you the most reliable information.
RSV Symptoms in Older Adults
Adults who catch RSV typically experience mild, cold-like symptoms and may never realize they have anything other than a seasonal bug. But adults over 65 face higher risks. RSV can progress to pneumonia in this age group, and it can also destabilize existing health conditions. People with asthma may see flare-ups. Those with COPD often experience worsening breathlessness. RSV can even strain the heart enough to worsen heart failure.
Because the initial symptoms are so generic, older adults and their families often underestimate RSV. A cold that lingers, deepens into a chest cough, or comes with increasing shortness of breath deserves a closer look, especially during RSV season (typically fall through spring).
How Long You’re Contagious
People with RSV are contagious for 3 to 8 days and can actually start spreading the virus a day or two before any symptoms appear. That pre-symptomatic window is one reason RSV moves through households and daycares so efficiently. Once symptoms resolve, most people stop being contagious. The exception is infants and immunocompromised individuals, who can shed the virus for 4 weeks or longer, even after they look and feel better.
RSV vs. Cold, Flu, and COVID-19
RSV, the flu, COVID-19, and the common cold all share overlapping symptoms: fever, cough, congestion, and sometimes shortness of breath. There is no reliable way to tell them apart based on symptoms alone. A cough with wheezing in a young child leans toward RSV, and sudden onset body aches and high fever lean toward the flu, but these are tendencies, not rules.
The only way to confirm which virus is causing the illness is a diagnostic test, which your healthcare provider can perform using a nasal swab. This matters most for infants, older adults, and anyone at higher risk for complications, because treatment decisions and monitoring depend on knowing the specific virus involved.
Warning Signs That Need Attention
Most RSV infections are mild, but certain symptoms indicate the virus has moved beyond the upper airways. In infants and young children, the red flags are difficulty breathing, pauses in breathing, a cough that is getting worse rather than improving, and poor fluid intake. A baby who is producing fewer wet diapers than usual may be getting dehydrated.
In adults, watch for shortness of breath that wasn’t there at the start of the illness, a gray or bluish tint to the lips or fingernails (a sign of low oxygen), and chest tightness. These symptoms suggest the infection has reached the lungs and may need more than home care to resolve.