hi i had gone through your query and understand your concerns. i would come up with two most possibilities to fit your condition .these include
1.first possibility is,HAND,FOOT,and MOUTH DISEASE;commonly caused by coxsackievirus and less commonly other type of virusus.
-swab culture may confirm the diagnosis.
management for prevention;
-washing hands well,esp after going to bathroom,changing diapers and handling diapers or other stool-soiled materials
-covering mouth and nose when coughing or sneezing
-washing toys and other surfaces that have saliva on them
2.second possibility is,
HERPES SIMPLEX;caused by herpes virus
-swab culture may confirm the diagnosis
I hope this is helpful for you, thank you