RSV, or Respiratory Syncytial Virus, is the most important respiratory organism of early childhood. RSV occurs throughout the world, and in each location it tends to occur in yearly winter outbreaks. In the northern hemisphere the peak of the epidemic is usually in January, February, or March, although in some years it may begin earlier and/or end later.

• Each year, around 100,000 infants are hospitalized with RSV in the United States alone.
  
  
• The virus lives inside the cells lining the respiratory system, causing swelling of this lining coupled with the production of large amounts of excess mucus.
  
  
• In adults, RSV shows up as a bad, lingering cold with thick nasal congestion and a deep, productive cough.
  
  
• In infants, the excess mucus can be enough to plug their small airways or bronchioles, resulting in a severe illness that requires hospitalization.
  
  
• Almost all children have had RSV by the time they are two years old.
  
  
• Children who first get it under 6 months of age (or who have serious underlying illnesses) are at the highest risk for severe disease.
  
  
• Thankfully, severe RSV infection is very uncommon in the first 6 weeks of life, since these babies still have antibodies from their mothers.
  
  
• The time period from exposure to illness is usually about 4 days.
  
  
• Typically a parent, or more likely an older sibling, comes down with a bad cold first.
  
  
• The disease spreads when infected droplets in the air or on the hands comes into contact with the baby's mouth or nose. (It has never been shown to be passed from someone standing as far as 6 feet away).
  
  
• The infant develops a runny nose and a red throat. Over the next 3 days or so the infant gets sicker.
  
  
• Symptoms include cough, wheezing, and sometimes a fever or an ear infection. In most infants, this is as severe as RSV gets. Some, though, will get progressively sicker with fast respirations (>60 per minute), difficulty breathing, and listlessness.
  
  
• About 3% of infected infants get sick enough to require hospitalization.
  
  
• The disease usually lasts 5 to 12 days.
  
  
• Two products are now available to prevent RSV infection in children at high risk for serious disease. RSV-IGIV (RespiGam) and palivizumab (Synagis) have been approved for children younger than 24 months with chronic lung disease/bronchopulmonary dysplasia or a history of premature birth (< 35 weeks).
  
  
• The best way to prevent RSV in other children is good hand-washing, particularly just before handling susceptible infants. Use a tissue when you cough or sneeze. If possible, avoid exposure to sick individuals during the peak of RSV season.
  
  
• Subsequent infections are usually less common and much less severe. Only about 15% of children over the age of 2 will have a case of RSV in each epidemic.
  
  
• Children who are sick enough to come to medical attention and be diagnosed with RSV have an increased chance of having recurrent wheezing later in life. This is even more likely if the child has eczema or if there is asthma in the family.
  
  
• The older a child is (over the age of 1) with severe RSV, the higher the likelihood that the child eventually will be diagnosed with asthma. It is not known whether it is the virus which damages the respiratory system and causes the asthma, or if it is people's susceptibility to asthma that predisposes them to severe RSV.
  
  
• A simple blood test that can predict which children are most likely to go on and develop asthma. Among children sick enough to be hospitalized with RSV, those who had a high eosinophil count had a 56% chance of developing asthma. The others with severe RSV had only a 22% chance. While RSV and asthma certainly go together, even with severe RSV and a high eosinophil count, there is a good chance of avoiding asthma altogether.