Child had mild chickenpox, <30 spots, no fever. i read it can be fatal in adults tho. take acyclovir or is this strain too mild to risk drug effects?

Only one strain: The reaction of kids to CPX varies from a few spots to hundreds, based on their own individual factors. The next kid/adult would react based on their own system. A cited 95% of adults in the US are immune, even if they have no memory of CPX. I would use acyclovir in an adult, but only if they developed a case.Incubation is 10-21 days starting the day before your kid broke out.