Don't be too paranoid. If that were the case, you wouldn't touch door handles, escalator hand rails, that you are strongly warned that if you don't keep hold of, the earth will stop rotating on its axis.......blah blah blah.
Take it all with a more than a grain of salt. Just about everything outside your house, and if you have toddlers within your 4 walls its much the same, is equally as "contaminated". Us humans aren't built to operate in a sterile environment. If we were, we would all be on the Moon.