RSV (respiratory syncytial virus) causes symptoms that look a lot like a common cold: runny nose, coughing, sneezing, congestion, and fever. Most people recover on their own within a week or two. But RSV can become serious in infants, older adults, and people with weakened immune systems, making it important to recognize when mild symptoms are heading in a dangerous direction.
Common RSV Symptoms
Symptoms typically appear 4 to 6 days after exposure. The standard list includes:
- Runny nose
- Congestion
- Coughing
- Sneezing
- Fever
- Wheezing
- Decreased appetite
In healthy older children and adults, these symptoms often feel indistinguishable from a regular cold. They tend to appear gradually rather than hitting all at once, which is one reason RSV can catch parents off guard. The illness may seem minor for the first couple of days, then worsen around days 3 through 5 before slowly improving.
How RSV Looks Different in Infants
Very young infants, especially those under 6 months, don’t always show the “classic cold” picture. Their only signs may be irritability, decreased activity, and difficulty breathing. They may not have an obvious runny nose or cough at all, which makes the illness easy to underestimate early on.
As RSV progresses in babies, more alarming breathing signs can develop. These include pauses in breathing (where the baby briefly stops for several seconds), flaring of the nostrils with each breath, and visible pulling or sucking in of the chest muscles between the ribs. These are signs of respiratory distress, and they mean the baby is working much harder than normal to get air. Reduced feeding is another red flag, since a baby who is struggling to breathe often can’t coordinate sucking and swallowing.
RSV is the most common cause of bronchiolitis (inflammation of the small airways in the lungs) and pneumonia in children under one year old. These complications are what drive most RSV-related hospitalizations. A baby who was mildly congested yesterday but is breathing rapidly, refusing to eat, or showing chest retractions today needs immediate medical attention.
RSV Symptoms in Adults and Older Adults
When adults get RSV, it typically stays mild and feels like a standard cold. Most don’t even realize they have RSV rather than another virus. The illness runs its course in about a week.
The exception is adults 65 and older, particularly those with underlying heart or lung conditions. In this group, RSV can progress to pneumonia. It can also trigger flare-ups of chronic conditions like asthma, COPD, and heart failure. An older adult whose “cold” suddenly involves significant shortness of breath, chest tightness, or worsening of a pre-existing condition may be dealing with more than a mild infection.
How RSV Differs From a Cold or the Flu
The early symptoms of RSV, a cold, and the flu overlap heavily, so telling them apart based on symptoms alone is difficult. That said, there are patterns worth knowing.
A cold tends to stay in the nose and throat. RSV is more likely to move into the lower airways, producing wheezing and labored breathing, especially in young children. The flu typically hits faster and harder, with prominent body aches, high fever, and fatigue that feel disproportionate to the congestion. RSV’s onset is more gradual. It starts looking like a cold and then, in vulnerable people, worsens over several days as the infection moves deeper into the lungs. That worsening trajectory is one of RSV’s distinguishing features.
How Long RSV Lasts and When You’re Contagious
Most people are contagious for 3 to 8 days, and you can actually start spreading the virus a day or two before symptoms appear. That pre-symptomatic window is one reason RSV moves so efficiently through daycares and households. Infants and people with weakened immune systems can remain contagious for 4 weeks or longer, even after their symptoms have cleared.
The full illness typically lasts 1 to 2 weeks. Symptoms tend to peak around days 3 to 5, then gradually improve. A lingering cough can stick around after the other symptoms have resolved, which is normal and doesn’t necessarily mean the infection is getting worse.
Prevention Options
RSV now has several preventive tools available, a relatively recent development. For infants, monoclonal antibody treatments (lab-made proteins that help the immune system fight the virus) are recommended to prevent severe disease. Pregnant women can receive a single dose of an RSV vaccine during weeks 32 through 36 of pregnancy to pass protection to their baby before birth.
For older adults, the CDC recommends a single dose of an RSV vaccine for everyone 75 and older, and for adults 50 to 74 who are at increased risk of severe illness. This is a one-time dose for now, so if you received it last season, you don’t need another one yet.
Beyond vaccines, RSV spreads through respiratory droplets and contaminated surfaces. Frequent handwashing, avoiding close contact with sick individuals, and keeping shared surfaces clean all reduce transmission, particularly during fall and winter when RSV circulates most actively.