Simplify the following text for a Grade 4 native English-speaking person.
Original: Haemophilia is rare , with only about 1 instance in every 10,000 births ( or 1 in 5,000 male births ) for hemophilia A and 1 in 50,000 births for hemophilia B. About 18,000 people in the United States have hemophilia .
Simplified: Haemophilia A happens in about 1 in 5,000 â `` 10,000 male births .