RSV

What RSV is, and its signs

RSV (respiratory syncytial virus) is a very common seasonal virus that infects the airways and lungs; nearly every child catches it at least once by around age 2. In older kids and healthy adults it usually feels like an ordinary cold. The reason it gets so much attention is that in babies it can move from the upper airway down into the small airways of the lungs and cause bronchiolitis (swelling of those tiny airways) or pneumonia, which makes RSV the leading reason infants in the U.S. are hospitalized. It mainly circulates in fall and winter, roughly October through March (timing varies by region and year), and spreads easily through coughs, sneezes, hands, and surfaces, so it moves fast through households and daycares. It often starts looking exactly like a cold: a runny or stuffy nose, less appetite, and sometimes a mild fever for a day or two, with a cough developing a day or three later. Signs that it's reaching the lungs include faster or harder breathing, wheezing (a high-pitched whistling on breathing out), and a worsening cough. Very young infants don't always follow this pattern; their main signs may be irritability, being unusually sleepy or less active, feeding poorly, or pauses in breathing (apnea), which can be one of the earliest signs in a newborn. Many babies with RSV never run a fever at all, so a normal temperature does not mean the lungs are fine.

Causes and who is most at risk

RSV is caused by the virus itself, spread through respiratory droplets and contaminated hands and surfaces; it is not caused by cold weather or by anything a parent did. Most healthy babies recover at home without trouble, but some are more likely to get seriously ill, and knowing this helps you decide how closely to watch and how quickly to call. Higher-risk groups generally include babies in their first 6 months (especially the first 2 to 3 months), infants born prematurely, and children with chronic lung disease, congenital heart disease, or weakened immune systems. Severity also isn't fixed in advance: a baby can look mild on day 1 or 2 and get noticeably worse around day 3 to 5, which is typically when breathing problems peak, so if your baby is higher-risk it's reasonable to check in with your pediatrician earlier rather than waiting.

Caring for it at home, and preventing it

There's no medicine that cures RSV, and antibiotics don't help because it's a virus, so home care is about keeping your baby comfortable, breathing as easily as possible, and well hydrated while the infection runs its course, usually over about 1 to 2 weeks. Suctioning the nose with saline drops and a bulb syringe before feeds and sleep can make a real difference, since babies breathe through their noses and a clogged nose makes feeding and sleeping hard. Offer feeds more often in smaller amounts; staying hydrated matters more than how much your baby eats. A cool-mist humidifier can help, and keeping your baby away from smoke is important. For fever or discomfort, ask your pediatrician about the right medicine and dose before giving anything: in babies under about 3 months, any fever should be evaluated by a provider rather than treated at home, so don't give acetaminophen to a young baby on your own; acetaminophen may be used in older babies, while ibuprofen is generally only for babies 6 months and older. Do not give over-the-counter cough and cold medicines to young children, and never give honey to a baby under 12 months. RSV is now largely preventable, so ask your provider about the maternal RSV vaccine in pregnancy or a long-acting infant antibody such as nirsevimab for your baby's first RSV season, plus everyday steps like frequent handwashing and keeping a young baby away from sick people and crowds in RSV season.

When to call the doctor, and the bottom line

Some RSV signs are true red flags. Call 911 or go to the ER right away if your baby is struggling to breathe, breathing very fast, has long pauses in breathing, or if their lips, mouth, tongue, or skin look bluish or gray. Other signs that need urgent care: the skin pulling in around the ribs, at the base of the neck, or under the breastbone with each breath; flaring nostrils or grunting with breaths; or a baby who is very hard to wake, limp, or won't stop being inconsolable. Call your pediatrician the same day for signs of dehydration (far fewer wet diapers, no tears when crying, a dry mouth, or a sunken soft spot), for poor feeding or refusing to drink, for any fever of 100.4F (38C) or higher in a baby under 3 months, or any time your gut tells you your baby is getting worse or just isn't right; because young babies can deteriorate quickly, never feel you have to 'wait and see' with breathing or feeding problems. The bottom line: most babies recover fine at home, but watch breathing and feeding closely (especially around days 3 to 5), know the red flags above, and keep a lower threshold for younger or higher-risk babies. This page is general information, not medical advice; your pediatrician or healthcare provider knows your baby and should guide any decisions about symptoms, medicines, and prevention.