RSV (respiratory syncytial virus) typically causes cold-like symptoms: runny nose, coughing, sneezing, fever, and decreased appetite. Symptoms show up 4 to 6 days after infection and appear in stages rather than all at once. Most cases clear up on their own in one to two weeks, but RSV can become serious in infants, older adults, and people with weakened immune systems.
Common Symptoms in Children and Adults
For most healthy older children and adults, RSV looks and feels like a regular cold. The core symptoms include a cough, stuffy or runny nose, fever, and a drop in appetite. You might also notice sneezing, a mild sore throat, or general fatigue. These symptoms tend to roll in gradually over a few days rather than hitting all at once, which is one reason RSV often gets mistaken for other respiratory viruses early on.
The illness typically peaks around days 3 to 5, then slowly improves. The cough can linger for a couple of weeks even after other symptoms resolve. In otherwise healthy people, RSV rarely needs anything beyond rest, fluids, and over-the-counter fever or pain relief.
Symptoms in Infants Under 6 Months
Very young infants don’t always show the obvious respiratory signs you’d expect. In babies under 6 months, RSV often presents as irritability, decreased activity, and eating or drinking less than usual. A parent might notice the baby refusing bottles, seeming unusually fussy, or sleeping more than normal before any coughing or congestion becomes obvious.
As the infection progresses, more recognizable signs can appear: wheezing, rapid breathing, flaring nostrils, and a visible tugging of the skin between or below the ribs with each breath (a sign the baby is working harder than normal to get air in). Pauses in breathing lasting more than 10 seconds can also occur in very young infants and require immediate attention. Because babies breathe primarily through their noses, even moderate congestion can make feeding difficult, which leads to dehydration on top of the infection itself.
Warning Signs That Need Urgent Care
Most RSV infections stay mild, but the virus can move into the lower airways and cause bronchiolitis (inflammation of the small airways in the lungs) or pneumonia. Watch for these signs that the infection is becoming more serious:
- Labored breathing: the skin pulls in around the ribs or at the base of the throat with each breath
- Fast, shallow breathing or noticeable wheezing
- Bluish color around the lips or fingernails, which signals low oxygen
- Significant drop in fluid intake or fewer wet diapers than usual in infants
- Worsening fever or a fever that returns after improving
These signs are most common in infants born prematurely, children under 12 months, and anyone with a compromised immune system. If you notice them in a child or vulnerable adult, that warrants a trip to the emergency room rather than a wait-and-see approach.
How RSV Affects Older Adults
Adults over 65 face a higher risk of serious RSV illness than the general adult population. The initial symptoms still look like a cold, but RSV can quickly worsen existing health conditions. It’s a known trigger for asthma flare-ups, COPD exacerbations (making it significantly harder to breathe in someone who already has limited lung function), and heart failure episodes where the heart struggles to pump enough blood and oxygen.
In older adults, the infection can also progress to pneumonia. The danger often isn’t the virus itself but how it destabilizes conditions that were previously under control. An older adult whose breathing worsens noticeably, who develops chest tightness, or who becomes confused or unusually drowsy during what seemed like a mild cold should be evaluated promptly.
RSV vs. Flu vs. COVID-19
All three viruses share a core set of symptoms (cough, fever, congestion, fatigue), which makes them nearly impossible to tell apart based on symptoms alone. That said, some patterns can offer clues.
The flu tends to hit suddenly and hard, with prominent body aches, chills, and headache alongside the respiratory symptoms. COVID-19 shares those features but is more likely to cause loss of smell or taste, shortness of breath, or gastrointestinal symptoms like nausea and diarrhea. RSV, by comparison, typically presents with a narrower set of symptoms: cough, fever, stuffy or runny nose, and reduced appetite, without the intense body aches or GI issues.
Wheezing is more characteristic of RSV than of flu or COVID, especially in young children. But the overlap is significant enough that lab testing is the only reliable way to confirm which virus is responsible. Both PCR tests (highly sensitive) and rapid antigen tests (faster but slightly less sensitive) can identify RSV specifically.
How Long RSV Lasts and When You’re Contagious
The incubation period is 4 to 6 days, meaning you’re likely exposed almost a week before you feel anything. Once symptoms appear, most people are contagious for 3 to 8 days, though infants and people with weakened immune systems can spread the virus for up to four weeks.
The overall illness typically runs its course in one to two weeks. Congestion and cough tend to be the last symptoms to fully resolve. If symptoms seem to improve and then suddenly worsen again around days 4 to 6, that can signal a secondary bacterial infection or progression to the lower lungs, and it’s worth getting checked out.
Prevention Options
RSV prevention has expanded significantly. For infants, monoclonal antibody treatments (a single injection that provides temporary immune protection) are recommended to prevent severe disease. Pregnant women can receive a maternal RSV vaccine between weeks 32 and 36 of pregnancy, which passes protective antibodies to the 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 due to chronic health conditions or a weakened immune system. This is a one-time dose for now; those who received it previously do not need a second one.