Diagnosis starts with the history and physical exam. This may be all that is needed to make the diagnosis. Given the common symptoms, RSV is likely if the child is younger than 1 year, if it is winter, and if there is a current outbreak of RSV in the community. A chest X-ray may help with the diagnosis and rule out other causes for the symptoms.
If needed, a special test called an immune assay can be done on nose or lung secretions to detect RSV. This is commonly done when children are admitted to a hospital so that outbreaks within the hospital can be limited.