Viral colds in children are self-limiting and usually last 3 to 5 days. It depends on the length of time it takes each child to develop antibodies to the viral infection, mostly about three days and up to seven days. Fevers caused by common viral infections that are upper respiratory tract infections will basically clear up in a week. Very few viruses can cause serious or persistent infections that require treatment with For example, influenza viruses need to be treated with oseltamivir.