My 19 month old son refuses to eat or drink and had a fever.Any causes/ solutions?

I took him to the ER on Tuesday b/c he had a fever of 104...then sent us home and said to continue monitoring.Then I took him to his Pediatrician and was told that it might be a virus and to come back if conditions dont improve...I know I took him to the park on sunday and the weekend before that,we took him to a outdoor party.He refuses to eat,drink...he doesnt even want his pacifier.Any advice on how to get him to atleast drink fluids ?