New U.S. and Congolese travel restrictions aimed at keeping Ebola from spreading across borders are drawing warnings from aid organizations and medical experts who say the measures could undermine efforts to control the world¡¯s fastest-growing outbreak of the virus.

The restrictions ¡ª introduced after a physician from humanitarian group Alima returned to France from eastern Democratic Republic of Congo with Ebola in June ¡ª threaten to slow the deployment and rotation of doctors, nurses and other specialists needed to contain the epidemic, according to aid groups and outbreak responders.

The U.S. now requires its citizens and nationals who have been in Congo to spend 21 days outside the country before returning on commercial flights, while Congo requires people leaving Ebola-affected areas to remain elsewhere in the country for three weeks before traveling internationally.