How do I know if it’s rsv vs a cold?

What the evidence says

Honestly, in the first few days you usually can't tell RSV from a regular cold, and Canadian sources say it's often not important to know which virus is causing it unless your child is at higher risk of complications. Both start with a stuffy or runny nose, mild cough, sore throat, and sometimes a low fever. What's different is what can happen next.

RSV is the most common cause of bronchiolitis (inflammation of the small airways) in babies and toddlers, so watch for the illness moving from a simple cold into faster or harder breathing, wheezing, flaring nostrils, ribs sucking in with each breath, grunting, poor feeding, or unusual fussiness or listlessness, especially in babies under 6 months. A cold usually stays mild throughout; RSV bronchiolitis often gets worse around day 3 to 5 before improving. In very young infants, RSV can also show up as just poor feeding, irritability, or pauses in breathing, without the classic cough and congestion, which is another reason it can look confusing at first.

If you do need a definite answer (for example your child is high risk, premature, or hospital care is being considered), a rapid antigen or PCR swab can confirm RSV specifically. For most healthy kids at home, though, the key is tracking breathing effort and hydration rather than trying to name the virus.