What does hand-foot-and-mouth disease (HFMD) look like? The symptoms can look different for kids and adults. See what the symptoms can be and how to treat them. What is Hand-Foot-and-Mouth Disease? HFMD is a common viral illness caused by the enterovirus, most commonly the coxsackievirus. The Centers for Disease Control and Prevention says the disease primarily affects children under 5, but anyone, including adults, can contract it. It’s typically a mild illness. The disease ...