strep throat is caused by a type of bacteria called group a beta-hemolytic streptococcus (gas). other bacteria or viruses can also cause a sore throat. people get strep throat by direct, close contact with a sick person. the illness can spread more easily when people are crowded together. examples of crowding include people in the military or in schools. the gas bacteria can dry out into dust, but then it cannot make people sick. if bacteria in the environment are keep moist they can make people sick for up to 15 days. moist bacteria can be found on things like toothbrushes. these bacteria can live in food, but this is very unusual. people who eat the food can become sick. twelve percent of children with no symptoms of strep throat have gas in their throats normally.