1. What is infant thrush? Infant thrush, also known as hand, foot and mouth disease, is an infectious disease caused by an enterovirus. The disease mainly affects infants and kindergarten children, with symptoms such as fever, oral ulcers, and skin lesions on hands and feet. 2. What are the early symptoms of infant oral thrush? After suffering from hand, foot and mouth disease, the earliest symptom is fever. Later, patients develop mouth sores and skin lesions. In the early stages, these ulcers usually appear on the tongue, lips, and cheeks