Respiratory syncytial virus
Respiratory syncytial virus, or RSV, is a common respiratory virus that usually causes cold-like illness but can lead to serious lung infection in infants, older adults, and higher-risk people.
What RSV is
Respiratory syncytial virus, often shortened to RSV, is a virus that infects the nose, throat, and lungs. For many people it feels like a cold, with mild symptoms that improve at home. In higher-risk people, RSV can move deeper into the lungs and cause bronchiolitis, pneumonia, or worsening of existing breathing problems.
How it spreads
RSV spreads through droplets and close contact when an infected person coughs, sneezes, or touches surfaces. The virus can enter through the eyes, nose, or mouth. It often spreads in households, childcare settings, schools, and healthcare or long-term care settings because people can pass it before illness is clearly recognized.
Symptoms
Symptoms often include runny nose, reduced appetite, cough, sneezing, fever, and wheezing. Very young infants may show irritability, decreased activity, poor feeding, or pauses in breathing rather than classic cold symptoms. Adults may have cold-like illness, but older adults or people with chronic conditions can develop shortness of breath or worsening disease.
Bronchiolitis and pneumonia
In babies and young children, RSV is a common cause of bronchiolitis, inflammation of the small airways in the lungs. It can also cause pneumonia. These lower-respiratory infections can make breathing fast, noisy, or labored and can lower oxygen levels. Severe cases may need hospital care, fluids, oxygen, or breathing support.
Who is at higher risk
Higher risk includes premature infants, very young infants, children with chronic lung disease or certain heart conditions, people with weakened immune systems, adults 65 and older, and adults with chronic heart or lung disease. RSV can also worsen asthma or COPD, which is why it matters beyond early childhood.
Testing and care
Clinicians may diagnose RSV from symptoms during a season when it is spreading, or use a nasal or throat swab when results affect care. Most infections are treated with supportive care such as fluids, fever management, suctioning for infants when advised, and monitoring breathing. Antibiotics do not treat RSV itself.
Prevention
Prevention includes hand hygiene, cleaning high-touch surfaces, staying home when sick, improving ventilation, and avoiding close contact with vulnerable people during illness. RSV prevention now also includes vaccines for some adults and pregnant people, and preventive antibody products for some infants and young children, depending on age, season, risk, and local guidance.
Why it matters
RSV matters because a familiar cold-like virus can become a serious breathing illness for the youngest, oldest, and most medically vulnerable people. Better prevention tools have changed the landscape, but timing, access, clear guidance, and recognition of warning signs still determine how much protection reaches real families.