Children's Hospital of Pittsburgh of UPMC recently released steps to avoid strep throat. Strep throat is most common in children in late fall, winter and early spring, according to Judith Martin, MD, an associate professor of Pediatrics at the University of Pittsburgh School of Medicine. Infection from Group A Streptococci (GAS)-the bacteria that causes strep throat-is spread by person-to-person contact, which makes children highly susceptible to spreading and getting the infection at school.