Coxsackie viruses are RNA viruses that may cause hand, foot, and mouth disease (HFMD). HFMD usually occurs in children but can occur in adults. The majority of HFMD infections are self-limited, so no treatment is required.Clinically, blisters that are painful usually on the hands, feet, and mouth in a child with fever are considered diagnostic of coxsackie virus infection. However, in rare instances, viral tests can be done to identify the virus, but the tests are expensive, usually need to be sent to a specialized viral diagnostic laboratory. He is refusing to drink because of ulcers in the mouth,and I usually give a mouth application to relieve pain. There is also the possibility of a super added bacterial infection for the recurrence of fever.Or he could have been infected by another virus.He needs to reviewed by his doctor.