Respiratory syncytial virus is the most common cause of bronchiolitis and pneumonia in US children under one year old, and it sends roughly 177,000 adults over 65 to the hospital every year according to CDC. For most healthy adults RSV looks like a bad cold. For infants, older adults, and immunocompromised people, the same virus can fill the small airways with mucus and cell debris until breathing becomes a struggle.

RSV used to live mostly outside public attention because there was nothing you could do about it. That changed in 2023. Two adult vaccines, a maternal vaccine, and a long-acting infant antibody all reached the US market within 18 months of each other. The math of who should get what is now the part most people get wrong. RSV is one piece of a layered infection prevention strategy that also covers respiratory hygiene, isolation, masks, and ventilation.

Key Takeaways

What is RSV and who's most at risk?

RSV is an enveloped RNA virus that infects the cells lining the nose, throat, and lungs. Almost every child encounters it by age 2, and most reinfections through life cause mild upper respiratory symptoms. Severe disease concentrates in three groups: infants under 6 months, adults over 65 (especially over 75), and people with chronic heart, lung, or immune conditions.

Premature infants face the steepest risk. A baby born at 32 weeks has airways the diameter of a coffee stirrer, and any swelling at all can collapse them. Long-term care residents are the adult equivalent. CDC data from the 2024-2025 season showed RSV-associated hospitalization rates above 200 per 100,000 in adults over 75, several times the rate in adults 60 to 64.

The seasonal pattern in temperate climates runs October through April with a peak in December or January. Tropical regions see year-round circulation with peaks tied to the rainy season. Our seasonal disease timing post lays out how RSV stacks against flu and COVID in the same window.

How does RSV present in infants vs adults over 60?

In babies under 12 months, RSV starts as a runny nose and mild cough and can progress to wheezing, fast breathing, chest retractions, poor feeding, and apnea over 2 to 4 days. In adults over 60, RSV looks like flu without the fever spike: cough, congestion, fatigue, and sometimes acute worsening of asthma or COPD that lands people in the emergency department.

Pediatric warning signs that warrant immediate medical attention: nostrils flaring with each breath, ribs visibly pulling in (intercostal retractions), grunting on exhale, bluish lips, or a baby too tired to feed. Apnea (pauses in breathing) is a specific RSV danger in infants under 3 months and is sometimes the first symptom before any cough appears.

In older adults, the giveaway is rapid functional decline. Someone who managed stairs fine a week ago is suddenly winded crossing a room. Pulse oximetry below 92% on room air, especially with cough, is hospital territory. Bacterial pneumonia often follows RSV in people over 75, which is why physicians keep watching for several days after the viral phase seems to clear.

How is RSV transmitted, and how long is it contagious?

RSV transmits through large respiratory droplets from coughs and sneezes, direct contact with infected secretions on hands or faces, and contaminated surfaces where the virus stays viable for up to 6 hours. People are typically contagious for 3 to 8 days, though infants and immunocompromised people can shed virus for up to 4 weeks.

That long shedding window in infants is why RSV rips through daycares and NICUs. A baby with a runny nose three weeks ago can still be infectious to a younger sibling. Surface contamination matters too. Toys, crib rails, doorknobs, and phones all become vehicles, which is why hand hygiene and surface disinfection are not optional during family illness.

Masks reduce but do not eliminate transmission. RSV particles are large enough that any well-fitted mask blocks most of them, and the mask comparison guide covers which types matter most when an older relative is staying with you during cold and flu season.

Who should get the RSV vaccine?

CDC recommends a single dose of any adult RSV vaccine (Abrysvo, Arexvy, or mResvia) for everyone 75 and older, and for adults 60 to 74 with chronic heart disease, chronic lung disease, severe obesity, diabetes, immunocompromise, or who live in a long-term care facility. Pregnant people should receive Abrysvo at 32 to 36 weeks gestation during RSV season to protect the newborn.

Adult RSV vaccines are not annual. As of the 2025-2026 season, CDC's recommendation is a single dose, with no booster guidance yet because durability data only goes out to 3 years. That is likely to change as more data accumulates. Across phase 3 trials published in NEJM, the three vaccines reported 82.6% (Arexvy), 85.7% (Abrysvo), and roughly 83% (mResvia) efficacy against RSV-associated lower respiratory tract disease in older adults.

For infants, the choice is between maternal vaccination during pregnancy or giving the baby Beyfortus (nirsevimab) at birth or before their first RSV season. Both prevent severe RSV disease. The infant-administered antibody is preferred when the mother was not vaccinated or when the birth fell outside the protective window.

How do you reduce RSV exposure during peak season?

Layer the same interventions that work for any respiratory virus: hand washing with soap and water for 20 seconds, well-fitting masks indoors during local RSV peaks, room ventilation through open windows or HEPA filtration, and isolating sick household members from infants and frail older adults. Vaccines and Beyfortus stack on top, not instead.

Childcare exposure is the single largest predictor of severe RSV in infants. Older siblings in daycare or preschool seed the household. If a household has both an infant and a daycare-age sibling, isolating the sibling at the first sign of a cold and increasing room ventilation is the most useful protective lever you have.

Hospital and long-term care facilities run their own infection control. For visitors, the practical move is staying home when you have any respiratory symptoms, and masking inside for the duration of any visit during peak RSV weeks. CDC posts current RSV activity by region, which is the data signal that should drive personal precautions.

FAQ

Can adults catch RSV more than once?

Yes. RSV immunity from natural infection wanes within months, and reinfection through adult life is normal. Most reinfections are mild. The vaccines for adults 60 and older are aimed at preventing severe disease, not reinfection itself, which is why the recommendation focuses on the populations most likely to be hospitalized rather than universal vaccination.

Is there a treatment for RSV?

For most people, treatment is supportive: fluids, rest, fever control, and managing breathing if it gets bad. Hospitalized infants may receive supplemental oxygen and IV fluids. Ribavirin and palivizumab are reserved for narrow indications. Beyfortus prevents disease but is not a treatment once symptoms start. New small-molecule antivirals are in late-stage trials.

How is RSV different from a cold or flu?

RSV, common cold viruses, and flu can all cause similar upper respiratory symptoms early. RSV more often progresses to wheezing and lower respiratory involvement in babies and older adults. Flu typically hits with sudden high fever and body aches. The only definitive way to tell is a PCR test, which most clinics now run as a combined panel.

Should I get the RSV vaccine if I had RSV recently?

CDC guidance does not require a delay for adults who recently had RSV. Natural infection produces shorter-lived immunity than the vaccine, and the vaccine remains effective even in people with recent exposure. Some clinicians wait 90 days after acute infection out of an abundance of caution, but this is preference rather than evidence-based policy.

Why is RSV worse for premature infants?

Smaller airways collapse under less swelling. A 32-week preemie has bronchioles roughly half the diameter of a term baby, so any inflammation or mucus has an outsized effect. Premature lungs also have fewer immune cells and incomplete surfactant production. Beyfortus is specifically prioritized for preterm infants and those with chronic lung disease of prematurity.