Strep throat is an infection of the throat and tonsils. Bacteria called group A streptococcus cause it. They live in the nose and throat. You can get the infection from someone who is sick with strep A bacteria or is a carrier of it. Like other infections, it spreads through close contact. When people who are sick cough or sneeze, they release droplets into the air that hold the bacteria. You can infect yourself if you touch something a person with strep has coughed or sneezed upon and then brush your eyes, mouth, or nose with your hand. You can also get sick if you share a glass or other personal item with someone who has strep. Strep is most common in children and teens. Adults can sometimes get it, too.