Baby has a fever, red pimples appear on the neck and face. What's going on?

After the baby has a fever, his face also has red pimples, which is likely to be the manifestation of acute childhood rash, which is a disease caused by human herpesvirus type 6 and 7 infection. In addition to acute childhood rash, there may be chickenpox, which is caused by varicella herpesvirus infection.