Per http://children.webmd.com/tc/hand-foot-and-mouth-disease-... :
"The virus spreads easily through coughing and sneezing. You can also get it by coming in contact with infected stool, such as when you change a diaper. Often the disease breaks out within a community. Children are most likely to spread the disease during the FIRST WEEK of the illness. But the virus stays in the stool and can sometimes spread to others for SEVERAL MONTHS after the blisters and sores have healed.
It usually takes 3 to 6 days for a person to get symptoms of hand-foot-and-mouth disease after being exposed to the virus. This is called the incubation period."
I know it's not what you wanted to see (can be spread for several months), but really- having been a childcare provider during an out break- not a big deal! There is a reason we are supposed to wear gloves while doing diapers and disinfect the changing table after every diaper!