RSV (Respiratory Syncytial Virus) is a common respiratory virus that usually causes mild, cold-like symptoms. It is a major cause of respiratory illness in children and can cause breathing problems in infants and young children. RSV symptoms usually appear within 4 to 6 days after getting infected and include a runny nose, coughing, sneezing, fever, wheezing, and a decrease in appetite. These symptoms usually appear in stages and not all at once. In very young infants with RSV, the only symptoms may be irritability, decreased activity, and breathing difficulties. RSV can also cause more severe infections such as bronchiolitis, an inflammation of the small airways in the lung, and pneumonia, an infection of the lungs. Infants, young children, and older adults are at increased risk of severe RSV. Almost all children will have had an RSV infection by their second birthday. If you or your child is having difficulty breathing, not drinking enough fluids, or experiencing worsening symptoms, it is important to call your healthcare professional. Seek immediate medical attention if your child has difficulty breathing, a high fever, or a blue color to the skin, particularly on the lips and in the nail beds.