What does it mean when childs stool is positive for pseudamonas but at the time no symptoms, now a month later has mild diarhea? colud it be virus?

Yes: Pseudomonas is an opportunist that can survive in many environments and be found as a "hitchhiker" germ in the stool.Its presence does not mean it is the infecting agent in this location.It is seldom a problem for anyone that does not have a compromised immune system.Were it to be found in sterile spaces like the blood or spinal fluid, it would always be considered an invader/infector.