RSV, or respiratory syncytial virus, typically starts with mild cold-like symptoms: runny nose, coughing, sneezing, fever, and decreased appetite. Symptoms usually appear 4 to 6 days after exposure. For most older children and healthy adults, RSV feels like an ordinary cold and clears up in one to two weeks. But in infants, older adults, and people with certain chronic conditions, the same virus can progress to serious breathing problems within days.
Early Symptoms in Children and Infants
RSV often begins looking unremarkable. A baby may develop a runny nose, mild cough, slight fever, and fussiness. They may eat or drink less than usual. At this stage, nothing obviously separates RSV from a dozen other respiratory viruses circulating during cold and flu season.
The concern with RSV is what happens next. The illness can become noticeably more severe a few days in. The cough deepens, breathing gets faster, and the child may start wheezing, a high-pitched sound when exhaling. Very young infants, especially those under 6 months, sometimes show subtler warning signs: unusually long pauses between breaths (apnea), extreme sleepiness, or a sharp drop in feeding. These babies may not cough much at all, which can make the illness easier to miss.
Signs the Infection Has Moved to the Lungs
RSV causes the most trouble when it spreads from the nose and throat down into the smaller airways of the lungs. In infants, this often leads to bronchiolitis, an inflammation of the tiny airways that makes breathing difficult. In both children and adults, RSV can also cause pneumonia, an infection of the lung tissue itself.
When this happens, breathing requires visible effort. Watch for these physical signs, particularly in infants and toddlers:
- Retractions: The skin pulls inward between the ribs or just below the collarbone with each breath, making the rib cage look more prominent.
- Nasal flaring: The nostrils widen noticeably each time the child breathes in.
- Grunting: A short “ugh” sound at the end of each breath, which is the body’s attempt to keep the airways open.
- Wheezing: A whistling or rattling sound, especially on exhale.
Rapid breathing is another red flag. Infants normally breathe faster than adults, but if a baby’s breathing looks labored, shallow, or unusually fast, that warrants immediate attention. A bluish tint around the lips or fingernails signals that oxygen levels have dropped and the child needs emergency care.
Dehydration is a secondary risk during severe RSV illness. Babies who are working hard to breathe often refuse to nurse or take a bottle. Fewer wet diapers than usual, a dry mouth, or crying without tears are signs that fluid intake has fallen too low.
Symptoms in Adults
Most adults with RSV experience a stuffy nose, dry cough, low-grade fever, sore throat, and general fatigue. It feels like a bad cold, and many people never realize they have RSV rather than another virus. Symptoms follow the same timeline: appearing about 4 to 6 days after exposure and resolving within a week or two.
The picture changes for adults over 60 or 65, especially those with underlying health conditions. RSV can trigger pneumonia or cause a significant flare of pre-existing problems like asthma, COPD, or heart failure. Difficulty breathing, chest pain or pressure, sudden confusion, and dizziness are all signs the infection has become serious. Adults in nursing homes are at particularly high risk because close living quarters make transmission easy and chronic health conditions are common.
How RSV Compares to Flu and COVID-19
RSV, influenza, and COVID-19 share enough symptoms that you generally cannot tell them apart by feel alone. All three can cause fever, cough, fatigue, and shortness of breath. A few patterns can offer rough clues: flu tends to hit suddenly with body aches and high fever, while RSV in adults leans more toward nasal congestion and a persistent cough. COVID-19 is more likely to cause loss of taste or smell, though that symptom has become less common with newer variants. In practice, a diagnostic test is the only reliable way to confirm which virus is responsible. Many clinics now offer combination tests that check for all three from a single nasal swab.
Who Is at Highest Risk
RSV sends tens of thousands of young children and older adults to the hospital each year in the United States. The groups most vulnerable to severe illness include premature infants, babies under 6 months, children under 2 with chronic lung disease or congenital heart conditions, adults 65 and older, and people with weakened immune systems.
Among adults, a range of chronic conditions raises the stakes. These include heart failure, COPD, emphysema, asthma, chronic kidney disease requiring dialysis, diabetes with organ damage, chronic liver disease like cirrhosis, sickle cell disease, severe obesity (a BMI of 40 or higher), and neurological conditions that weaken the muscles used for breathing or coughing.
How RSV Is Diagnosed
If your symptoms or your child’s symptoms are mild, testing usually isn’t necessary since treatment is the same regardless of which cold virus is involved. When symptoms are severe enough to warrant a clinic or emergency room visit, two main types of tests are used. PCR-based tests are highly sensitive and detect even small amounts of the virus from a nasal swab. Rapid antigen tests deliver results faster, sometimes in under 30 minutes, but are less sensitive, meaning they occasionally miss infections. Your provider will choose based on the clinical situation.
Vaccines and Prevention
RSV vaccines are now available for adults. The CDC recommends a single dose for all adults 75 and older, and for adults 50 to 74 who have conditions that put them at increased risk. Three vaccines are currently licensed for this age group. The vaccine is not annual like the flu shot. One dose is considered complete, and no booster is currently recommended.
For those who haven’t been vaccinated, the best time to get the shot is late summer or early fall, typically August through October, just before RSV season peaks. However, eligible adults can be vaccinated at any time of year. For infants, preventive options include an antibody injection given during their first RSV season, which provides passive protection for several months. Pregnant individuals can also be vaccinated during pregnancy to pass protective antibodies to the baby before birth.
Basic hygiene measures help reduce spread at any age: frequent hand washing, avoiding close contact with sick individuals, and keeping shared surfaces clean. RSV spreads through respiratory droplets and can survive on hard surfaces for several hours, so wiping down countertops, doorknobs, and toys during cold season makes a meaningful difference, especially in households with infants or older adults.