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The Centers for Disease Control and Prevention on Wednesday ramped up its response to the expanding Ebola outbreak, a move that frees up hundreds of employees and signals the agency sees the health emergency as a potentially long and serious one.

The CDC’s “level 1 activation” is reserved for the most serious public health emergencies, and the agency said the move was appropriate considering the outbreak’s “potential to affect many lives.” The CDC took a similar move in 2005 in the aftermath of Hurricane Katrina, and again in 2009 during the bird-flu threat.

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The Ebola outbreak is believed to have killed 932 people in the African nations of Liberia, Sierra Leone, Nigeria and Guinea. Two American aid workers sickened by the disease were flown back to the U.S. for treatment at a medical facility in Atlanta.

The CDC is deploying additional staff to the four affected countries, and said 50 more disease-control experts should arrive there in the next 30 days. It also issued instructions to airlines that may come into contact with passengers from the affected countries designed to minimize the chance of infection.

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.@CDCEmergency Ops Center moved to Level 1 response to #EbolaOutbreak given the extension to Nigeria & potential to affect many lives. — Dr. Tom Frieden (@DrFriedenCDC) August 6, 2014

We thank God Nancy Writebol arrived safely in Atlanta and is now being treated at Emory Hospital. Learn more here: http://t.co/LfWstRosxI — Samaritan's Purse (@SamaritansPurse) August 5, 2014

— Phil Helsel