But nearly every child in the United States will come down with the virus by age 3, and some parents need to worry about it. RSV is responsible for about 125,000 infant hospitalizations and 4o0 deaths each year -- 10 times more infant fatalities than the flu.
The virus attacks the tiny bronchioles in infant lungs, causing fever and difficulty breathing that is one step short of pneumonia, Checchia said. It runs from November to March. In other words, the season is now.
Most at risk are the 500,000 babies born prematurely in the United States each year, before 36 or 37 weeks of gestation. Their underdeveloped lungs have narrow, fragile airways, and they lack the complete complement of antibodies that full-term infants have. Also at risk, Checchia says, are babies with lung, heart and neurological conditions.
The virus "attacks their lungs at a time when they're most vulnerable," he said. "You need to know about this as a parent because it is something that is so ubiquitous in the population."
Symptoms include persistent coughing or wheezing, fast or troubled breathing, spread-out nostrils or a caved-in chest when the baby is trying to breathe, a bluish color around the mouth or fingernails and a rectal temperature of more than 100.4 Fahrenheit in infants less than 3 months old.
There is no treatment, but there quite a few ways to minimize risk of transmission. Parents of young children should wash their hands frequently and ask others to do the same, Checchia said, as well as keep toys, clothes, blankets and sheets clean. The virus can live on toys and hard surfaces such as kitchen counters for short periods of time. Avoid crowds, and ask your pediatrician if your child is at high risk for infection. There are prophylactic efforts that can strengthen infants' immune sysems, Checchia said.
The virus usually runs a 10- to 14-day course. So if a baby with those symptoms is not improving in three to five days, it's time to consult a physician.