U.S. Defense Secretary Chuck Hagel delivers the keynote address to the Association of U.S. Army annual meeting in Washington October 15, 2014.  REUTERS/Jonathan Ernst (UNITED STATES - Tags: POLITICS MILITARY) - RTR4ABMX
U.S. Defense Secretary Chuck Hagel delivers the keynote address to the Association of U.S. Army annual meeting in Washington October 15, 2014. REUTERS/Jonathan Ernst (UNITED STATES - Tags: POLITICS MILITARY) - RTR4ABMX

PENTAGON - Secretary of Defense Chuck Hagel has ordered all U.S. troops returning from Ebola response missions in West Africa to be placed in supervised isolation for 21 days.

The Pentagon calls the isolation a safety measure sought by military members' families.

Pentagon spokesman Colonel Steve Warren says the U.S. military has about 1,100 troops in Liberia and Senegal supporting efforts to combat the virus.

"The Department has the largest population of Americans operating in Africa," he said. "Our personnel who are operating there are not medical professionals, as are a majority of the other citizens and civilians who are operating there. And so we believe that conducting a more tightly controlled monitoring program on the way out of Africa is in the best interest of our force and of our families and of the country."

The move goes beyond precautions recommended for civilians by the Obama administration.

Secretary Hagel acted in response to a recommendation sent to him Tuesday by the Chairman of the Joint Chiefs of Staff on behalf of the heads of each of the military services.

The secretary has directed that the Joint Chiefs develop a detailed implementation plan within 15 days to lay out how the military will apply this controlled monitoring across the force.

He also has directed the Joint Chiefs to conduct a review of this new regimen within 45 days to see whether or not the controlled monitoring should continue based on the reviews' observations.