Clinically, in bacterial tonsillar infection, one can see changes in the tonsil like follicles, pus, larger crypts, etc. but in viral infection the tonsils are only congested. The general symptoms for both are more or less the same. These differences are not fixed. The only thing you need to remember is that bacterial tonsillar infection is recurrent and may have raised blood counts (WBC, ASLO, etc.) but the viral type is episodic and the blood changes are reverse, unless complicated with bacterial infection.