A second Cuban doctor is confirmed to have defected from a controversial program to bring thousands of medical professionals to underserved regions of Brazil, according to Brazilian health officials.

"To all my friends on Facebook who sent me messages of concern about my absence, I thank you," said a message posted to a Facebook profile under the doctor's name, Ortelio Jaime Guerra. Brazil's health ministry confirmed on Monday that Mr. Guerra stopped showing up to work last week in Pariquera Açu, a small town in the...