You can refer to the white blood cell count in a routine blood test, and although it is not absolutely accurate to determine the type of infection directly, it can serve as a preliminary diagnosis in most cases.
Elevated white blood cells can be seen in bacterial infections, with neutrophil elevation being the most pronounced. In viral infections, the leucocytes are elevated and the lymphocytes are predominantly elevated, in which case cytomegalovirus infection or EBV infection is likely. When an upper respiratory tract viral infection is present, it may trigger neutropenia and a decrease in total white blood cell count.