About Tonsillitis: Making the Diagnosis
Open your mouth and say "aaah". The tonsils can be seen at the back of the throat, and will be clearly red and inflamed. There's a tendency for different infectious agents to cause different types of inflammation. Epstein-Barr virus, for example, often causes tiny red spots on the soft palate due to miniature internal bleeds. Bacteria may leave a thin white membrane on the tonsils themselves that peels off easily. None of these symptoms, however, are reliable enough to diagnose the infectious agent from appearance alone, so a throat swab is needed. Traditionally, such swabs are then cultured to see what bacteria are present, but there are also rapid smear tests that can give results in minutes or hours. There's also a smear test for mononucleosis. Flu viruses can sometimes be detected in the blood, but this test is very unlikely in tonsillitis. Finding group A strep on the tonsils doesn't prove it's causing the inflammation, since so many people carry this bug with no ill effects. The person could be a healthy strep carrier whose tonsillitis is due to undetected cold viruses.