Irritability cough and a runny nose in an infant?

Depends on . . .: Babies ages 3-12 months can easily catch colds from other people. If there is just a runny nose, without much fussiness, without any high fever, without other worrisome symptoms, then parents can leave the nose alone. If the mucous is blocking the nose somewhat, try a few drops of saline, followed by gentle suctioning with a suction bulb. A doctor should examine younger or more symptomatic babies.

Likely viral: But any infant who has those symptoms should be examined by his/her pediatrician.