Signs and symptoms of respiratory syncytial virus infection most commonly appear about four to six days after exposure to the virus. In adults and older children, RSV usually causes mild cold-like signs and symptoms. These include:

• Congested or runny nose
• Dry cough
• Low-grade fever
• Sore throat
• Mild headache

In severe cases

Respiratory syncytial virus infection can spread to the lower respiratory tract, causing pneumonia or bronchiolitis — inflammation of the small airway passages entering the lungs. Signs and symptoms may include:

• Fever
• Severe cough
• Wheezing — a high-pitched noise that's usually heard on breathing out (exhaling)
• Rapid breathing or difficulty breathing — the child may prefer to sit up rather than lie down
• Bluish color of the skin due to lack of oxygen (cyanosis)

Infants are most severely affected by RSV. You may notice your child's chest muscles and skin pull inward with each breath. This is a sign that he or she is struggling to breathe. Other signs and symptoms of severe RSV infection in infants include:

• Short, shallow and rapid breathing
• Cough
• Poor feeding
• Unusual tiredness (lethargy)
• Irritability

Most children and adults recover in one to two weeks, although some might have repeated wheezing. Severe or life-threatening infection requiring a hospital stay may occur in premature babies or infants and adults who have chronic heart or lung problems.

Respiratory syncytial virus enters the body through the eyes, nose or mouth. It spreads easily through the air on infected respiratory droplets. You or your child can become infected if someone with RSV coughs or sneezes near you. The virus also passes to others through direct contact, such as shaking hands.

The virus can live for hours on hard objects such as countertops, crib rails and toys. Touch your mouth, nose or eyes after touching a contaminated object and you're likely to pick up the virus.

An infected person is most contagious in the first few days after infection. However, the virus may continue to spread for up to a few weeks.

By age 2, most children will have been infected with respiratory syncytial virus. Children who attend child care centers or who have siblings who attend school are at a higher risk of exposure. RSV season — when outbreaks tend to occur — is the fall to the end of spring.

People at increased risk of severe or sometimes life-threatening RSV infections include:

• Premature infants
• Young children who have congenital heart or lung disease
• Children with weakened immune systems, such as those undergoing chemotherapy or transplantation
• Infants in crowded child care settings
• Older adults
• Adults with asthma, congestive heart failure or chronic obstructive pulmonary disease
• People with immunodeficiency, including those with certain transplanted organs, leukemia or HIV/AIDS

Complications of respiratory syncytial virus include:

• Hospitalization. A severe RSV infection may require a hospital stay so that doctors can monitor and treat breathing problems and give intravenous (IV) fluids.
• Pneumonia. RSV is the most common cause of inflammation of the lungs (pneumonia) or the lungs' airways (bronchiolitis) in infants. These complications can occur when the virus spreads to the lower respiratory tract. Lung inflammation can be quite serious in infants, young children, immunocompromised individuals, or people with chronic heart or lung disease.
• Middle ear infection. If germs enter the space behind the eardrum, you can get a middle ear infection (otitis media). This happens most frequently in infants and young children.
• Asthma. There may be a link between severe respiratory syncytial virus in children and the chance of developing asthma later in life.
• Repeated infections. Once you've had RSV, it's common for the infection to come back. It's even possible for it to happen during the same RSV season. However, symptoms usually aren't as severe — typically it's in the form of a common cold. But they can be serious in older adults or people with chronic heart or lung disease.