Streptococcus pyogenes, also known as group A streptococcus, causes strep throat, an infection of the throat and tonsils. Bacteria like this live in the nose and throat. It is possible to contract the infection from someone who is sick with strep A bacteria or who is carrying it.   The spread of strep throat is similar to that of other infections. The bacteria in the air is spread through coughing or sneezing by sick people.   By touching something that has been coughed or sneezed upon by someone with strep, and then brushing your eyes, mouth, or nose with your hand, you can infect yourself. Additionally, you can get sick if you share a glass or other personal item with someone who has strep throat.   The most common cause of strep throat is childhood and adolescence. It sometimes affects adults as well.