<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by Meckel syndrome ? [/INST] Meckel syndrome affects 1 in 13,250 to 1 in 140,000 people worldwide. It is more common in certain populations; for example, the condition affects about 1 in 9,000 people of Finnish ancestry and about 1 in 3,000 people of Belgian ancestry. </s>