RSV, or respiratory syncytial virus, is a common respiratory infection that inflames the airways and lungs. Nearly every child catches it by age 2, and most recover within a week or two. But for infants, older adults, and people with weakened immune systems, RSV can become serious enough to require hospitalization. In the 2024-2025 season alone, RSV caused an estimated 190,000 to 350,000 hospitalizations in the United States.
How RSV Spreads and Takes Hold
RSV is an enveloped RNA virus in the Pneumoviridae family. It spreads the same way as a cold: through respiratory droplets when an infected person coughs or sneezes, through direct contact like kissing a child’s face, or by touching a contaminated surface and then touching your eyes, nose, or mouth.
Once the virus reaches the cells lining your airways, it hijacks their machinery to make copies of itself. The virus wraps its genetic material in a protective protein shell that hides it from your immune system’s early-warning sensors, giving it a head start before your body mounts a defense. As infection spreads deeper into the smaller airways, inflammation and mucus buildup can make breathing difficult, especially in very small lungs.
People with RSV are typically contagious for 3 to 8 days, sometimes starting a day or two before symptoms appear. Infants and people with compromised immune systems can shed the virus for 4 weeks or longer, even after they seem to have recovered.
Symptoms and How They Progress
In most children and adults, RSV looks and feels like a bad cold. The first signs are usually a runny nose and decreased appetite. Coughing develops 1 to 3 days later, followed by sneezing, fever, and sometimes wheezing. Very young infants may not follow this pattern. Instead, they may become unusually irritable, sluggish, or have brief pauses in breathing (called apnea).
For healthy older children and adults, symptoms typically peak around day 3 to 5 and resolve within 1 to 2 weeks. The cough can linger. In infants under 6 months and adults over 65, though, what starts as mild congestion can progress to labored breathing, flared nostrils, and a visible pulling-in of the chest muscles with each breath. These are signs the infection has moved into the lower airways.
Who Faces the Highest Risk
Hospitalization rates tell a clear story about who RSV hits hardest. During the 2024-2025 season, infants under 12 months had the highest hospitalization rate of any age group, followed by toddlers aged 12 to 23 months. Among adults, those 75 and older were most vulnerable. Of the 672 RSV-associated deaths recorded that season, 82% occurred in adults 65 and older.
Beyond age, several conditions raise your risk of severe illness: chronic heart or lung disease, diabetes with organ complications, kidney disease requiring dialysis, neurological conditions that weaken the muscles used for breathing or swallowing, chronic liver disease, sickle cell disease, severe obesity (BMI of 40 or higher), and moderate to severe immune compromise. Living in a nursing home is also a significant risk factor.
Bronchiolitis, Pneumonia, and Long-Term Effects
The two main complications of RSV are bronchiolitis and pneumonia. Bronchiolitis is inflammation of the smallest airways in the lungs (the bronchioles), which swell and fill with mucus. It’s the leading cause of hospitalization in infants under 1. Pneumonia occurs when the infection reaches the air sacs of the lungs themselves, making gas exchange harder and sometimes requiring supplemental oxygen.
There’s also growing evidence that RSV in infancy has consequences that outlast the infection. A Vanderbilt University study that followed nearly 1,400 children for five years found that 21% of those infected with RSV in their first year of life developed asthma by age 5, compared to 16% of those who avoided RSV as infants. That translates to a 26% higher risk of early childhood asthma. Researchers estimate roughly 15% of asthma cases by age 5 could be prevented by avoiding infant RSV infection. The working theory is that RSV disrupts lung and immune system development during a critical window in the first year of life.
How RSV Is Diagnosed
Two main types of tests detect RSV. Rapid antigen tests give results quickly but are less sensitive, meaning they can miss some infections. Molecular tests like PCR are highly sensitive and the most reliable way to confirm RSV, though results take longer. In many cases, especially for otherwise healthy adults, doctors diagnose RSV based on symptoms alone since the treatment approach is the same regardless of which respiratory virus is responsible.
Managing RSV at Home
There is no antiviral medication for RSV. Treatment is supportive, meaning the goal is to keep the person comfortable and hydrated while their immune system clears the virus. For most people, that means rest, fluids, and over-the-counter fever reducers.
For infants with congestion, gentle nasal suctioning with a bulb syringe or mouth-operated nasal aspirator (like a NoseFrida) can help clear the nasal passages. Saline drops or spray before suctioning helps loosen thick mucus. Deep suctioning with a catheter pushed far into the nose should be avoided at home, as it can irritate the airways and actually prolong illness. Watch feeding closely: babies who are breathing fast or struggling to breathe may have trouble coordinating sucking and swallowing safely. Smaller, more frequent feedings can help.
Signs that warrant immediate medical attention in an infant include rapid breathing, flaring nostrils, the skin between or below the ribs pulling inward with each breath, a bluish tint to the lips or fingernails, and significant difficulty feeding or signs of dehydration like fewer wet diapers.
Vaccines and Preventive Treatments
RSV prevention has changed dramatically in recent years. Three options now exist depending on your age and situation.
For adults 75 and older, the CDC recommends a single dose of RSV vaccine. Adults between 50 and 74 with conditions that increase their risk of severe RSV (the chronic conditions listed above) are also recommended to get vaccinated. Three vaccines are available for this age group, made by GSK, Moderna, and Pfizer, with no preference among them. This is not an annual shot. One dose is considered complete for now, and the best time to get it is late summer or early fall (August through October in most of the continental U.S.), just before RSV season begins.
For infants, a preventive antibody called nirsevimab (brand name Beyfortus) offers protection without requiring the baby’s own immune system to build a response. A single injection provides ready-made antibodies that neutralize the virus. In the 2024-2025 season, nirsevimab was 77% effective at preventing RSV-related hospitalization in infants. This is particularly significant given the link between infant RSV and later asthma risk.
Pregnant individuals can also receive an RSV vaccine during weeks 32 through 36 of pregnancy, which passes protective antibodies to the baby before birth. This maternal vaccine and nirsevimab serve the same purpose, so infants typically receive one or the other rather than both.