RSV, or respiratory syncytial virus, typically starts looking like an ordinary cold before it can escalate into serious breathing problems, especially in infants and older adults. Knowing the difference between normal cold symptoms and warning signs that need immediate attention can help you act quickly when it matters. Most RSV infections clear up on their own in one to two weeks, but a small percentage progress to dangerous territory.
How RSV Symptoms Typically Unfold
Symptoms usually appear four to six days after exposure. They don’t all hit at once. Instead, they tend to roll in over several days, starting mild and sometimes building in intensity.
The early stage looks like any other upper respiratory infection: a runny nose, sneezing, mild cough, and possibly a low fever. Appetite often drops, particularly in babies. Within one to three days, the virus can spread from the nose and throat down into the smaller airways of the lungs. That’s when things can shift. If the infection stays in the upper airways, you’re likely looking at a standard cold that resolves without complications. If it moves into the lower airways, you may start to notice wheezing, a worsening cough, and visible effort with each breath.
What Happens Inside the Airways
RSV targets the tiny tubes deep in the lungs called bronchioles. Once the virus infects cells lining those airways, it triggers inflammation, swelling, and a surge of mucus production. Damaged cells and debris from the immune response slough off into already narrowed, mucus-filled passages, creating blockages. In adults and older children, these airways are wide enough to tolerate some swelling. In infants, the passages are so small that even modest inflammation can cause significant obstruction, which is why babies wheeze and struggle to breathe far more easily than older kids with the same virus.
Breathing Signs That Signal Trouble
This is the most important section if you’re caring for a young child with RSV. Breathing changes are what separate a manageable illness from one that needs emergency care. Here’s what to watch for:
- Retractions: The skin pulls inward just below the neck, under the breastbone, or between the ribs with each breath. This means the body is working hard to pull air into partially blocked lungs.
- Nasal flaring: The nostrils spread wide open with each inhale, another sign of increased breathing effort.
- Grunting: A short grunting sound at the end of each exhale. The body does this reflexively to keep the lungs inflated and open.
- Wheezing: A high-pitched whistling sound, particularly on exhale, indicating narrowed airways.
- Fast or labored breathing: In infants, a breathing rate consistently above 60 breaths per minute is concerning. You can count by watching the chest rise for 30 seconds and doubling the number.
Any of these signs, especially in combination, means the illness has moved beyond what you should manage at home.
When to Go to the Emergency Room
Three situations call for immediate emergency care: difficulty breathing that doesn’t improve, a high fever (particularly above 100.4°F in babies under two months old), and any bluish color on the lips, fingernails, or skin. That blue tint, called cyanosis, means oxygen levels have dropped to a dangerous point. Don’t wait to see if it passes.
Dehydration is another serious concern, particularly in infants who are too congested or too exhausted to feed. If your baby is producing noticeably fewer wet diapers than usual, seems unusually lethargic, or refuses to eat for several feedings in a row, those are signs that the illness is overwhelming their ability to stay hydrated.
Who Is Most at Risk for Severe RSV
Severe RSV disease most commonly strikes very young infants, including healthy babies with no underlying conditions. That’s a point many parents miss. You don’t need a pre-existing health problem for RSV to become dangerous in a newborn. Beyond healthy infants, several groups face elevated risk:
For children, the higher-risk categories include premature babies, children with weakened immune systems, those with neuromuscular conditions that make it hard to cough up mucus or clear their airways, and children with severe cystic fibrosis or congenital heart disease.
For adults, the risk profile shifts. All adults 75 and older are considered at increased risk for severe RSV. Adults between 50 and 74 face heightened risk if they have chronic heart disease, chronic lung conditions like COPD or asthma, diabetes with organ damage, severe obesity (BMI of 40 or higher), liver cirrhosis, sickle cell disease, kidney disease requiring dialysis, or moderate to severe immune suppression. Living in a nursing home is also an independent risk factor.
What RSV Looks Like in Older Adults
RSV doesn’t only affect babies. In older adults, it can mimic a bad cold or flu before worsening into pneumonia or triggering flare-ups of existing heart or lung disease. The warning signs are similar to what you’d watch for in children: increasing shortness of breath, wheezing, persistent fever, and unusual fatigue or confusion. Because RSV in seniors is often mistaken for flu or a general respiratory decline, it tends to be recognized later in the course of illness. If an older adult with chronic heart or lung disease develops a worsening cough with increasing breathlessness, RSV should be on the radar, especially during fall and winter months.
How RSV Is Diagnosed
Two main types of tests detect RSV. PCR-based tests (similar to what became familiar during COVID) are highly sensitive and work well across all age groups. Rapid antigen tests are faster but less sensitive, meaning they can miss some infections. Both are done with a nasal swab. Testing isn’t always necessary for older children and healthy adults with mild symptoms, but it becomes important when the illness is severe enough to affect treatment decisions, particularly in hospitalized infants or high-risk adults.
Caring for RSV at Home
Most RSV infections resolve without medical intervention. The main priorities during home care are keeping the airway as clear as possible, maintaining hydration, and monitoring for the breathing red flags described above. For infants, a bulb syringe or nasal aspirator can help suction mucus from the nose before feedings. Saline drops can loosen thick secretions. Offering smaller, more frequent feedings helps babies who tire easily.
For both children and adults, staying well hydrated is the single most important home care measure. Fever and increased breathing rate both accelerate fluid loss. In babies, tracking wet diaper output gives you a reliable gauge. A noticeable drop from their normal pattern is an early signal that fluid intake isn’t keeping up.
Over-the-counter fever reducers appropriate for the person’s age can help with comfort. Avoid cough suppressants in young children, as coughing helps clear mucus from the airways.
Prevention Options
Preventive treatments now exist for infants and older adults. A protective antibody called nirsevimab is available for babies entering their first RSV season, providing passive immunity that lasts through the peak months. Pregnant women can also receive an RSV vaccine during pregnancy to pass protective antibodies to their baby before birth. For older adults at increased risk, RSV vaccines are available and recommended based on age and underlying health conditions. Coverage rates are still climbing. CDC survey data from the 2024-25 season shows that uptake of infant protection, whether through maternal vaccination or nirsevimab, has been gradually increasing but remains far from universal.
Basic hygiene measures also matter: frequent handwashing, avoiding close contact with visibly sick people, and keeping infants away from crowds during peak RSV season (typically November through March in most of the U.S.) all reduce transmission risk.