Respiratory syncytial (RSV) is a virus that often causes mild cold-like symptoms. However, in some cases, it can lead to more serious infections, such as bronchiolitis or pneumonia. Infants and older adults are at higher risk of developing severe RSV and may require hospitalization. 

RSV vaccines are available to protect older adults against the disease. Pregnant people can also receive RSV vaccine to provide protection through passive immunity for their infants and young children.