RSV (respiratory syncytial virus) spreads through respiratory droplets when an infected person coughs, sneezes, or talks. You can also pick it up by touching a contaminated surface and then touching your face. Most people encounter RSV for the first time as young children, but the virus can reinfect you throughout your entire life because the immunity it triggers is short-lived and incomplete.
How RSV Gets Into Your Body
The virus travels in tiny droplets expelled from the nose and mouth of someone who’s infected. If those droplets land on your eyes, nose, or mouth, the virus can take hold. Close contact is the most common route: kissing a child’s face, sharing cups or utensils, or simply being nearby when someone coughs.
RSV can also survive on hard surfaces like doorknobs, countertops, and toys. If you touch one of these surfaces and then rub your eyes or nose, you give the virus a path in. This is one reason RSV tears through daycares and households so efficiently. Young children touch everything, put their hands in their mouths constantly, and aren’t great at covering coughs.
Once the virus reaches your airways, it latches onto the cells lining your respiratory tract using a protein on its surface. It specifically targets the tiny, hair-like cells (ciliated cells) that normally sweep mucus and debris out of your lungs. After attaching, a second viral protein fuses the virus’s outer layer with the cell membrane, letting the virus slip inside and start replicating. In infants, RSV can also infect certain immune cells, which may partly explain why babies often carry higher amounts of the virus and get sicker.
Contagious Period and Incubation
After exposure, symptoms typically appear within 4 to 6 days. But a person can start spreading RSV a day or two before any symptoms show up, which makes it difficult to avoid. The contagious window usually lasts 3 to 8 days in healthy older children and adults.
Infants and people with weakened immune systems are a different story. They can shed the virus for 4 weeks or longer, sometimes even after their symptoms have cleared. This extended shedding is a major reason RSV circulates so persistently in hospitals, nursing homes, and households with young babies.
Why You Can Get RSV More Than Once
Unlike some viruses that grant lasting immunity after a single infection, RSV offers only temporary, partial protection. In a study that tracked adults after a confirmed RSV infection, about half were reinfected within just 2 months when exposed to the same strain. By 8 months, two-thirds had been reinfected. Within 26 months, nearly three-quarters had caught RSV at least twice, and almost half had three or more infections.
Your body does produce antibodies after an RSV infection, and higher antibody levels do correlate with some resistance. But even people with the strongest antibody responses still had a 25% chance of reinfection when exposed. The protection is real but far from complete and fades quickly. Two infections close together seem to extend the immune protection somewhat, but not enough to prevent future rounds entirely. This is why RSV remains a lifelong concern rather than a one-and-done childhood illness.
Who Gets Hit Hardest
Almost everyone contracts RSV by age 2. For most healthy adults and older children, it feels like an ordinary cold. The people at greatest risk for severe illness fall into a few specific groups.
Infants under 2 months old face the highest hospitalization risk. RSV is the leading cause of hospitalization among all U.S. infants. Their airways are tiny, their immune systems are immature, and the inflammation RSV causes can make breathing genuinely difficult. Premature babies and those with chronic lung disease or heart conditions face even greater danger.
Other high-risk groups include children with severe immune deficiencies, cystic fibrosis with significant lung involvement, and children of American Indian or Alaska Native descent, who experience higher rates of severe RSV for reasons that likely involve a combination of genetics, healthcare access, and environmental factors. Older adults, particularly those over 60 with chronic heart or lung disease, are also vulnerable to serious complications.
When RSV Circulates
In most of the continental United States, RSV follows a seasonal pattern that peaks between late fall and early spring, roughly October through March. This overlaps with flu season, which is part of why winter feels like a nonstop stretch of illness for families with young children. In tropical and subtropical regions, the timing can shift, and some areas see RSV activity year-round.
The seasonal pattern matters because it shapes when preventive measures are most important: more frequent handwashing, keeping sick family members away from infants, and cleaning commonly touched surfaces.
Prevention Options
Basic hygiene goes a long way. Washing hands frequently, avoiding touching your face, and staying away from people who are visibly sick reduce your chances of picking up RSV. For parents of newborns, asking visitors to wash their hands before holding the baby and avoiding crowded indoor spaces during peak season are practical steps.
For infants, there are now two main prevention strategies. Pregnant women can receive an RSV vaccine during pregnancy, which passes protective antibodies to the baby before birth. Alternatively, infants under 8 months entering their first RSV season can receive a long-acting antibody injection that provides direct protection for several months. Most babies need one or the other, not both. If the mother was vaccinated at least 14 days before delivery, the infant typically does not need the additional injection.
Children between 8 and 19 months who are at increased risk, including those with chronic lung disease, severe immune problems, cystic fibrosis with serious lung involvement, or American Indian and Alaska Native children, are recommended to receive the antibody injection before their second RSV season as well. These injections are generally given between October and March to align with peak RSV circulation.
For older adults aged 60 and up, RSV vaccines are also available and recommended based on individual risk factors like chronic lung or heart disease.