The viruses that cause tonsillitis are often the ones that frequently affect the respiratory (breathing) system. They include the flu (influenza) virus, the parainfluenza virus (which causes laryngitis and croup), as well as the adenovirus, the enterovirus, and the rhinovirus.

In rare cases, tonsillitis can develop as a result of the Epstein-Barr virus which is the virus that causes glandular fever. If this is the case, it is likely that you will feel quite ill. You may have swollen lymph nodes (glands) throughout your body and an enlarged spleen.

Bacterial tonsillitis may be caused by a number of different bacteria, but the most common ones are group A streptococcus bacteria.

It is spread by close contact, sneezing etc. through droplet infection.