RSV is most dangerous at the two extremes of life: babies under 6 months old and adults 75 and older. Between those groups, anyone with chronic heart or lung disease or a weakened immune system also faces serious risk. For most healthy children and adults, RSV causes cold-like symptoms that resolve on their own, but in vulnerable age groups it can lead to hospitalization, intensive care, or death.
Why Babies Under 6 Months Face the Greatest Risk
Infants younger than 3 months have the highest risk of severe RSV illness. Their airways are tiny, and when the virus infects the smallest branches of the lungs (the bronchioles), swelling and mucus buildup can block airflow much more easily than in an older child or adult. Their immune systems are also still developing, so they can’t fight off the infection as effectively.
This shows up clearly in hospitalization numbers. During the 2024-25 RSV season, the hospitalization rate for infants under 12 months was roughly 1,050 to 1,117 per 100,000, far higher than any other age group. Children 12 to 23 months old had the next highest rate, around 650 to 770 per 100,000, dropping steeply from there. In very young infants under 6 months, one unique warning sign is apnea, where the baby stops breathing for more than 10 seconds. This doesn’t typically happen in older children with RSV.
The Risk Window From 6 Months to 2 Years
RSV remains a concern through age 2, though the danger drops considerably after 6 months. Children between 6 months and 2 years still have relatively small airways, and reinfection is common because a first bout of RSV doesn’t create lasting immunity. Kids in this age range who were born prematurely, have congenital heart disease, chronic lung disease, or neuromuscular conditions that weaken their ability to cough and clear mucus are at especially high risk of landing in the hospital.
By age 2, most children have been infected with RSV at least once. After that point, repeat infections generally cause milder symptoms resembling a common cold.
Adults 65 and Older
RSV gets far less attention as an adult illness, but it causes an estimated 60,000 to 160,000 hospitalizations and 6,000 to 10,000 deaths each year among adults 65 and older in the United States. During the 2024-25 season, RSV was associated with an estimated 10,000 to 23,000 deaths across all ages, with older adults accounting for a large share.
Among hospitalized adults 60 and older, CDC surveillance data shows that about 17% required intensive care, nearly 5% needed a mechanical ventilator, and roughly 5% died. More than half of hospitalized patients were 75 or older. People living in long-term care facilities made up about 17% of all hospitalized cases, reflecting how congregate settings and frailty compound the risk.
The conditions most commonly seen alongside severe RSV in older adults were obesity, chronic obstructive pulmonary disease (COPD), congestive heart failure, and diabetes.
Conditions That Raise Risk at Any Age
Age alone doesn’t tell the full story. Several underlying conditions can make RSV dangerous regardless of how old you are:
- Chronic lung or heart disease, including COPD, asthma, heart failure, and congenital heart defects
- Weakened immune systems from cancer treatment, organ transplant, or conditions like HIV
- Neuromuscular disorders such as muscular dystrophy that make it harder to cough or breathe deeply
- Premature birth, because the lungs and immune system had less time to develop
- Severe obesity (BMI of 40 or higher)
- Chronic kidney or liver disease
A 50-year-old with COPD, for instance, may face RSV risks similar to a healthy 75-year-old.
How Prevention Lines Up With Age
Because the danger is so concentrated at specific ages, prevention strategies are targeted accordingly.
For Newborns and Infants
Babies can be protected in two ways. Pregnant women can receive a single dose of the Abrysvo vaccine between 32 and 36 weeks of pregnancy, which passes protective antibodies to the baby before birth. Alternatively, infants younger than 8 months entering their first RSV season can receive an antibody injection (nirsevimab) that provides direct protection. This approach has made a measurable difference: hospitalization rates among infants under 8 months dropped by 28% to 43% during the 2024-25 season compared to pre-prevention years, with the largest reduction (up to 52%) seen in babies under 3 months.
Children between 8 and 19 months who have conditions putting them at higher risk can receive a second-season dose as well.
For Older Adults
The CDC recommends a single RSV vaccine for all adults 75 and older, and for adults 50 to 74 who have conditions that increase their risk of severe illness. Three vaccines are currently available. It is not an annual shot; one dose is considered sufficient for now. Timing it for late summer or early fall, before RSV season peaks, gives the best protection.
Warning Signs in Infants
If you have a baby under 6 months, knowing what to watch for matters more than it does for older children. RSV often starts looking like a regular cold with a runny nose and mild cough. In young infants, it can progress to visible signs of breathing difficulty: the skin between the ribs or below the ribcage pulls inward with each breath, the nostrils flare, and breathing becomes unusually fast or labored. Pauses in breathing lasting more than 10 seconds are a particularly urgent sign in very young infants and are specific to this age group. Refusal to feed or significant decrease in wet diapers also signals that the infection is becoming more than a routine cold.