Note the moderate redness of the oropharynx, i.e., soft palate, and tonsillitis caused by group A streptococcus bacteria.

Strep throat is caused by group A streptococcus bacteria. These bacteria are spread through direct contact with mucus from the nose or throat of persons who are infected, or through contact with infected wounds or sores on the skin.

Picture & text from CDC/PHIL. For more information see Strep Throat Pictures from CDC