RSV, or respiratory syncytial virus, is a common respiratory infection that affects the lungs and airways. For most healthy adults and older children, it feels like a bad cold. But for infants, young children, and older adults, it can become serious enough to require hospitalization. During the 2024–2025 season alone, RSV caused an estimated 190,000 to 350,000 hospitalizations and 10,000 to 23,000 deaths in the United States.
How RSV Differs From a Common Cold
RSV and the common cold share a lot of early symptoms: runny nose, sore throat, headache, and low-grade fever. That overlap makes the two hard to tell apart in the first day or two. But RSV tends to move deeper into the lungs in a way that ordinary colds usually don’t.
The clearest difference is wheezing, a tight whistling sound when you breathe. That’s a hallmark of RSV and much less common with a standard cold. Another distinguishing pattern is the direction your symptoms take. A cold generally peaks around day three or four and then starts improving. With RSV, symptoms often get worse over the first several days rather than better, particularly the cough and any breathing difficulty.
Symptoms in Infants vs. Adults
In babies and toddlers, the infection typically starts with a runny nose and decreased appetite. A cough develops one to three days later, followed by sneezing, fever, and wheezing. Very young infants may not show the classic respiratory symptoms at all. Instead, they can become unusually irritable, lethargic, or experience pauses in breathing (called apnea), which can be alarming for parents who aren’t expecting it.
In healthy adults, RSV often passes as a mild upper respiratory illness that resolves in a week or two. But adults over 75, and those with chronic heart disease, lung disease, diabetes with complications, severe obesity, or weakened immune systems are at significantly higher risk of severe illness. Among recorded RSV deaths in the 2024–2025 season, 82% occurred in adults 65 and older.
Timeline and Contagiousness
After exposure, symptoms typically appear within a few days. You become contagious a day or two before symptoms start and generally remain contagious for 3 to 8 days. That pre-symptomatic window is one reason RSV spreads so easily through households and daycare settings. Infants and people with weakened immune systems can shed the virus for four weeks or longer, even after they look and feel better.
Why RSV Is Dangerous for Babies
RSV is the leading cause of bronchiolitis (inflammation of the small airways in the lungs) and pneumonia in children under one year old. The hospitalization rate for infants under 12 months is roughly 1,117 per 100,000, the highest of any age group. Children aged 12 to 23 months are the next most affected, at about 771 per 100,000.
Babies’ airways are tiny. When the lining of those airways swells and fills with mucus, even a modest amount of inflammation can make breathing difficult. A severe RSV infection in infancy also appears to leave a lasting mark. Research supported by the National Institute of Allergy and Infectious Diseases found that infants who avoided RSV infection in their first year of life had a 26% lower risk of developing asthma by age five compared to those who were infected.
Signs of a Breathing Emergency
Most RSV infections resolve on their own, but the virus can cause respiratory distress that needs immediate medical attention. In both children and adults, the warning signs are:
- Retractions: the skin pulls inward below the neck, under the breastbone, or between the ribs with each breath, as the body works harder to pull air in
- Nasal flaring: the nostrils spread wide open during breathing
- Color changes: a bluish or grayish tint around the mouth, inside the lips, or on the fingernails, signaling low oxygen
- Rapid breathing rate
- Cool, clammy skin with increased sweating, especially on the head
If you notice any combination of these, especially in an infant, that warrants emergency care.
Caring for RSV at Home
There is no antiviral medication that treats RSV. Recovery is about supporting the body while it fights off the infection, which typically takes one to two weeks.
For infants, keeping the nose clear makes a real difference because babies breathe primarily through their noses. A drop or two of saline in each nostril, followed by gentle suction with a bulb syringe, can help. Over-suctioning irritates the nasal lining, so sometimes saline alone is enough to trigger a sneeze that clears things out. Breast milk or formula are the best fluids for babies because they provide both hydration and nutrition.
For older children and adults, hydration is the priority. Water, diluted juice, soup, popsicles, and water-rich foods like watermelon all count. If a child isn’t eating much, make sure their fluids contain some salt and sugar. Milk does not make mucus worse, despite the persistent belief that it does. Over-the-counter fever reducers can help with discomfort, and a cool-mist humidifier may ease congestion.
Prevention: Vaccines and Immunizations
RSV prevention has changed significantly in recent years, with new options for both the youngest and oldest patients.
For Infants
An antibody called nirsevimab is recommended for all infants younger than 8 months who are born during or entering their first RSV season, provided their mother did not receive a maternal RSV vaccine during pregnancy. CDC data shows it is 90% effective at preventing RSV-related hospitalization in infants during their first season. It’s given as a single injection and provides protection throughout the peak months.
For Adults
A single dose of RSV vaccine is now recommended for all adults 75 and older, and for adults 50 to 74 who have conditions that raise their risk. Those conditions include chronic heart or lung disease, diabetes with organ damage, severe obesity (BMI of 40 or higher), weakened immune systems, chronic liver or kidney disease, neurologic conditions that affect breathing or swallowing, and residence in a nursing home. Three vaccines are available for this age group, with no preference among them. The RSV vaccine is not an annual shot. One dose is considered a complete course for now.