Good pediatricians do not prescribe antibiotic for viral infections. Viruses are very simple creatures. Viruses are very good at this and multiply in the body very rapidly. They invade and take over our normal cells and force them to help in the viral reproduction. This causes all of our symptoms because their reproduction kills the host cells.
Kids get so many viruses simply because there are so many viruses to get.
There are more than 100 varieties of rhinovirus, the agent that causes the common cold. There are more than 60 varieties of enteroviruses, one of the agents that causes vomiting and diarrhea. There are dozens of viruses, each of which have many, many varieties. That is why we keep getting colds. Even if we develop immunity to one of the cold viruses, there are a hundred more waiting to make us sick.