<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by Y chromosome infertility ? [/INST] Y chromosome infertility occurs in approximately 1 in 2,000 to 1 in 3,000 males of all ethnic groups. This condition accounts for between 5 percent and 10 percent of cases of azoospermia or severe oligospermia. </s>