Group A streptococcus (group A strep) is a type of bacteria (Streptococcus pyogenes) that can cause many types of different infections and illnesses in people, ranging from minor illnesses like “strep throat” or pharyngitis, to very severe invasive infections like necrotizing fasciitis and streptococcal toxic shock syndrome. The bacteria may be spread through direct and indirect contact contact with respiratory secretions that contain the bacteria.