Every winter in clinics across the country a steady procession of children with coughs, runny noses, fevers and headaches files through.
Despite all those symptoms, a report in the New England Journal of Medicine says doctors failed to properly diagnose flu infections in more than 75 percent of preschoolers.
That's because few doctors use a nasal swab test that provides results in less than 30 minutes and costs $30 to $50.
"It is a relatively expensive test. I think they haven't recognized how often it might be positive and that's really the major effect of this paper," said Dr. Stephen Baum at New York's Beth Israel Medical Center.
With roughly 8 million children under the age of 5 suffering from the flu each year, misdiagnosis puts a lot of other family members at risk too.
Children who are diagnosed within the first 48 hours of catching the flu can be given antiviral medications that can reduce a bout with the disease by one day.
And antiviral medications can be given to other family members to protect them from catching the flu. Studies show such drugs are 75 percent to 85 percent effective at preventing influenza.
But the reality is that there are not nearly enough of these medications for every family that might benefit from using them. Doctors say the best thing parents can do to protect themselves and their children from the sickness is get an annual flu shot.
And beginning this year, a Centers for Disease Control and Prevention panel has recommended that flu shots be given to children from 6 months to 5 years old.