How long does RSV last?
Most RSV infections in otherwise healthy infants and children last 1–2 weeks from first symptoms to full recovery. But the illness doesn't feel linear — it typically worsens before it gets better, and the cough can linger for a frustratingly long time after everything else clears up.
The typical RSV timeline
Days 1–3: Upper respiratory phase
RSV presents first as a runny nose, mild cough, and sometimes a low-grade fever. This phase is indistinguishable from a common cold. Babies generally remain active and feeding reasonably well, though they may be fussier than usual.
Days 3–5: The peak (watch this window)
This is the window when RSV is most dangerous, especially for young infants. Symptoms can escalate — the cough deepens, breathing may become faster, wheezing may appear. Feeding often decreases. If RSV is going to progress to bronchiolitis, it usually happens in this window.
RSV typically peaks around day 4–5. If your baby is under 6 months and symptoms are worsening on days 3–4, stay in close contact with your pediatrician.
Days 5–7: The plateau and turn
For most infants, symptoms begin to plateau and then slowly improve after day 5. Fever resolves, feeding gradually returns, and the baby begins to seem more like themselves. Breathing usually normalizes before the cough does.
Days 7–14: Cough lingers
The cough from RSV can persist for 2–3 weeks after the acute phase resolves. This is normal and expected — the airways are still recovering. As long as the cough is improving (less frequent, less intense) and your baby is otherwise well, a lingering cough is not typically a concern.
A cough that worsens after day 7, or that is accompanied by return of fever or new breathing difficulty, warrants a call to your pediatrician. Secondary infections (like ear infections or pneumonia) can develop.
Timeline for hospitalized infants
Infants who need hospitalization for RSV (for oxygen support or hydration) typically stay 2–5 days. Discharge usually happens when SpO₂ is stable on room air and feeding is adequate. Recovery at home after discharge may still take another week for the cough and energy levels to return fully.
Contagiousness
RSV is contagious from shortly before symptoms appear through about 3–8 days of illness. The virus spreads through respiratory droplets and by touching contaminated surfaces. Careful hand-washing and avoiding sharing utensils or cups is the best way to prevent household spread. There is no proven benefit to isolating a child with RSV within the household — it typically spreads before you know what it is.
Immunity after RSV — does it last?
No. Unlike some viruses, RSV does not produce lasting immunity. Children and adults can be reinfected with RSV every year. Reinfections in older children and adults are typically mild — the immune system has enough memory to prevent severe disease but not reinfection entirely. This is also why Beyfortus only protects for one season and why adult RSV vaccines were developed.
Will my baby's lungs be affected long-term?
Research suggests that severe RSV bronchiolitis in infancy may be associated with increased risk of recurrent wheezing and asthma later in childhood. Whether RSV directly causes this, or whether infants with underlying airway sensitivity are simply more likely to have severe RSV, is still being studied. If your child has had severe RSV and you notice ongoing wheezing or respiratory symptoms in the months after, bring it up with your pediatrician.
Not medical advice. If your infant's symptoms worsen or you're concerned, contact your pediatrician.