Respiratory Syncytial Virus (RSV)
Page last updated 10/30/2026.
The County of San Diego is dedicated to preventing vaccine-preventable diseases by following the West Coast Health Alliance’s (WCHA) recommendations for vaccinations based on credible, transparent, and science-based evidence.
Respiratory Syncytial Infection, or RSV, is a common respiratory virus that usually causes mild, cold-like symptoms.
RSV can be dangerous for infants and adults who are older or have certain risk factors. It is the most common cause of bronchiolitis (inflammation of the small airways in the lungs) and pneumonia (infection of the lungs) in children younger than 1 year of age in the United States. RSV can also make chronic health problems worse.
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RSV can spread when:
- A person who has RSV coughs or sneezes near you.
- Droplets from a cough or sneeze get in your eyes, nose, or mouth.
- You have direct contact with someone with RSV, like kissing the face of a child with RSV.
- You touch a surface that has the virus on it, like a doorknob, and then touch your face before washing your hands.
People with RSV can start spreading the virus a day or two before they feel sick, and they can spread it to others for 3 to 8 days. But some infants and people with weak immune systems can still spread RSV for 4 weeks or longer, even after they stop feeling sick.
Children often catch RSV outside the home, like at school or childcare centers.
Risk Factors
Many people get RSV for the first time as an infant or toddler. Almost all children have had it by age 2. Most people will get better in a week or two, but RSV can be serious for infants and young children, and adults who are older or have certain risk factors.
People at highest risk for severe RSV disease include:
- Infants and young children (the younger the age, the higher the risk).
- American Indian and Alaska Native children.
- Children born prematurely.
- Children with congenital (from birth) heart disease or chronic lung disease (e.g., asthma).
- Children with weakened (compromised) immune systems.
- Children with severe cystic fibrosis.
- Children with neuromuscular disorders.
- Adults with weakened (compromised) immune systems.
- Older adults (ages 75 and older), especially those who have heart or lung disease.
- Adults with other underlying medical conditions.
- Adults living in nursing homes.
People infected with RSV usually show symptoms within 4 to 6 days after getting infected.
Symptoms of RSV infection usually include:
- Runny nose
- Congestion (e.g., stuffy nose)
- Decrease in appetite
- Coughing
- Sneezing
- Fever
- Wheezing
These symptoms usually show up one at a time, not all at once. In very young infants with RSV, the only signs might be fussiness, being less active, and trouble breathing.
Call a healthcare provider if you or your child are having trouble breathing, not drinking enough fluids, or have symptoms that are getting worse.
County of San Diego
California Department of Public Health
Centers for Disease Control and Prevention
County of San Diego
California Department of Public Health
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Call the Immunization Unit at (866) 358-2966, or send an e-mail, for more information.
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