Atlanta ? Two U.S. heart transplant patients who died earlier this year had contracted a parasitic tropical disease from their new organs, health officials reported Thursday.

The two California men are the fourth and fifth U.S. patients believed to have been infected with Chagas’ disease through organ transplants, according to the Centers for Disease Control and Prevention.

Organ donors are screened for Chagas’ in South America, where the disease is much more common. No screening test for Chagas’ is licensed in the U.S.

The two men, ages 64 and 73, died at separate Los Angeles hospitals after being treated with Chagas’-fighting drugs from a special CDC stockpile of medicines not available in this country.

The infected organs came from one person born in Central America and another who had traveled to Mexico, the CDC reported.