|MadSci Network: Virology|
I can understand your concern. In short, germs live outside the body anywhere from a few seconds to 48 hours. Flus tend to live longer on surfaces than colds. The best thing to do is to teach your child to regularly wash his hands. That will be your best line of defense along with maintaining a healthy diet.
If you are truly concerned that something may be festering in the playdoh you can rub an alcohol hand sanitizer (not too much as it contains alcohol) on the playdoh. Colds and flus spread by person-to-person contact more so than by surface contact.
I would like to reassure you that colds and flus live longer on hard surfaces than they do on porous surfaces such as playdoh. I hope they are not putting the playdoh in their mouth.
If you need any further information, please let me know.
All my best,
Mayo Clinic Information on Germs
CDC Snort, Sniffle, Sneeze
Try the links in the MadSci Library for more information on Virology.