"Usually we begin seeing the early cases of RSV around the end of November, but the real push starts in December," says Deborah Lehman, MD, associate director of pediatric infectious diseases and HIV at Cedars-Sinai Medical Center.

"Unless they've had a baby who has been hospitalized with the disease or a premature infant who requires prophylaxis, I'd say most parents don't have a good sense of what this virus is."

According to the American Academy of Pediatrics, about 125,000 children are hospitalized in the United States each year with RSV, making it the #1 cause of infant hospitalization. Likewise, RSV is the leading cause of pneumonia and bronchiolitis (a swelling of the small airways) and may be associated with wheezing. Fortunately, the majority of children who contract RSV are treated as outpatients but, of those who require hospitalization, approximately 500 die each year.

The virus is highly contagious and can live for several hours on a surface such as a countertop, table or playpen, or on unwashed hands.

The first symptoms of RSV, Lehman explains, are the same symptoms as a cold: runny nose, a cough and a low-grade fever and typically disappear on their own within five to seven days. Signs of a more serious infection are wheezing, fast breathing and/or difficulty in breathing, irritability and restlessness, poor appetite and a fever of 100.4 degrees or higher, although some babies do not have a fever. If your child shows any of the signs of a serious infection, Lehman recommends that you contact your pediatrician.

"This virus can be particularly detrimental to babies who are born more than four weeks prematurely, or those who have gone home after staying in the neonatal intensive care unit because of some type of chronic lung disease," adds neonatologist Charles Simmons, MD, Chair of the Department of Pediatrics and Director of the Division of Neonatology at Cedars-Sinai. Those children who fall within the American Academy of Pediatrics' guidelines for RSV immunization are eligible for a prophylactic medication (brand name Synagis) that is given as a series of monthly injections usually beginning in mid-October and provide the infant immunity from the disease when the season begins. The injections usually continue for five months, until the season wanes.

"But if a child is eligible for the immunizations and hasn't started yet, it still would be beneficial this season for them to begin taking them," Simmons advises. He cautions parents to remember that children who are immunized against RSV do not develop long-lasting immunity to the virus. "You can actually get RSV several times during your life."

Adults can get RSV too, adds Lehman, hoarseness being a common symptom that may go unrecognized as a sign of the virus. In the last five to ten years RSV has been found to be a significant cause of morbidity in older patients with compromised pulmonary systems. Adults may serve as an important reservoir in the community, infecting more vulnerable infants.

If your child isn't eligible for RSV immunization, there are some precautions you can take to prevent exposure to RSV and other viruses, especially in the first few months of your baby's life. Among the American Academy of Pediatrics recommendations are:

• Make sure everyone washes their hands before touching your baby.
• Keep your baby away from anyone who has a cold, fever or runny nose.
• Keep your baby away from crowded areas like shopping malls.
• Keep your baby away from tobacco smoke. Parents should not expose their infants and young children to secondhand tobacco smoke, which increases the risk of and complications from severe viral respiratory infections.
• All infants between six and 23 months of age should be immunized against influenza. The influenza vaccine also may help protect children against other very common respiratory viruses.

"The understanding of RSV as a viral disease and the development of a specific therapeutic strategy that lead to the development of Synagis (RSV prophylaxis) is a story," says Simmons, "that we hope is repeated over and over again for various other viral pathogens. This shows that it is possible to substantially reduce the morbidity and mortality of certain disorders in the highest risk groups. I think this is a real success story."