RSV is a respiratory virus that infects the lungs and breathing passages. Although it can affect anyone, RSV is generally considered as the most frequent cause of lower respiratory tract infections in infants and young children. Each year an estimated 57,527 children younger than 5 years old are hospitalized due to RSV infection in the United States.

Symptoms of RSV are similar to other respiratory infections. Illness begins 4 to 6 days after being exposed to the virus. In adults and older children, typical RSV symptoms include a low-grade fever, congested or runny nose, cough, sore throat, headache, fatigue, and occasionally wheezing. In children younger than age 2, RSV can cause a lower respiratory tract illness such as bronchiolitis or pneumonia; more severe cases can result in respiratory failure. For people with severe illness, symptoms may include a worsening croupy cough, unusually rapid breathing, difficulty breathing, and a bluish color of the lips or fingernails caused by low levels of oxygen in the blood. RSV can cause middle ear infections (otitis media) in preschool children. 

RSV infections occur all over the world, most often in outbreaks that can last up to 5 months, from late fall through early spring. RSV epidemics spread easily in households, daycare centers, and schools.

Most children are infected at least once by age 2 and continue to be reinfected throughout life. RSV is the most common cause of bronchiolitis and pneumonia in children younger than 1 year of age. The majority of children hospitalized for an RSV infection are under the age of six months. The elderly (those 65 years of age and older), premature infants, persons with chronic lung or heart problems, or persons with weak immune systems are at higher risk for developing serious illness. Those who are exposed to tobacco smoke, attend daycare, live in crowded conditions, or have school-aged siblings could also be at higher risk. 

The virus is found in discharges from the nose and throat of an infected person. People can get RSV infection by breathing in droplets after an infected person has coughed; by hand-to-mouth contact after touching an infected  person; and by hand-to-mouth after touching a surface that an infected person has touched or coughed on. The time period from exposure to illness is usually 4 to 6 days. After an infection, a person may be contagious for 3 to 8 days. However, some infants and people with weakened immune systems can spread the virus for up to 4 weeks.

There are steps that you can take to prevent the spread of RSV. If you have cold-like symptoms:

• Cover your cough and sneezes with a tissue, sleeve, or elbow.
• Wash your hands often and correctly (with soap and water for 20 seconds).
• Avoid sharing cups and utensils with other people.
• Do not kiss other people.
• Clean contaminated surfaces such as doorknobs and countertops with a disinfectant.

Other steps that may be taken to the prevent the spread of RSV are:

• Stay home when you are sick. 
• Avoid exposure to sick persons, especially those that have cold-like symptoms. If possible, parents with high-risk young infants should avoid crowds.
• Limit the time that high-risk children spend at their school or child-care center during the RSV season.

Consult with your healthcare provider. Any breathing difficulties in an infant should be considered an emergency, so seek immediate help.

The diagnosis is usually made by the pattern of a child's symptoms (a clinical diagnosis), especially if he or she has a cold and is wheezing. RSV can be confirmed by checking for the virus in nasopharyngeal specimens or by growing the virus from nasal swabs, nasal washes, or tracheal secretions.

There is currently no vaccine to prevent RSV infection. Researchers are working to develop RSV vaccines.  Because RSV infection is often resolved on its own, treatment of mild symptoms is not necessary for most people. For babies    and children who are at high risk of developing severe RSV, preventive medication is available. Parents of an infant who is premature, has a chronic lung or heart condition, or has a weak immune system should contact their doctor or healthcare provider. Antibiotics are not useful in the treatment of RSV or any other viral disease.

RSV is common worldwide, but no additional precautions are needed when traveling. The number of infections usually peaks in the late fall, winter, and early spring in the United States and Europe. In tropical climates, epidemics occur during the rainy season.