St. Louis ? The families who host the nearly 30,000 foreign exchange students who stay in this country each year now will have to undergo criminal background checks, under new federal rules that went into effect this week.

Under the State Department rules, exchange student programs also will be required to tell the students how to identify and report sexual abuse and to notify the department and local law enforcement of any reports of abuse.

The new State Department rules were publicly proposed last summer and went into effect Thursday.

The acting director of the State Department’s Office of Exchange Coordination and Designation, Stanley Colvin, said last year it had received only five reports of abuse.