<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by Duchenne and Becker muscular dystrophy ? [/INST] Duchenne and Becker muscular dystrophies together affect 1 in 3,500 to 5,000 newborn males worldwide. Between 400 and 600 boys in the United States are born with these conditions each year. </s>