Highest alert for an all-hands on deck response to the Ebola crisis in West Africa was issued by the US Centers for Disease Control and Prevention on Wednesday.
"Ops Center moved to Level 1 response to given the extension to Nigeria & potential to affect many lives," CDC chief Tom Frieden said on Twitter.
Level 1 is the highest on a 1-6 scale and signals that increased staff and resources will be devoted to the outbreak.
He said it was the first time since 2009 that the Level 1 alert had been issued. Back then it was in response to the outbreak of H1N1 flu.
West Africa is experiencing the largest outbreak of the hemorrhagic fever in history.
A total of 932 people have died since March in Sierra Leone, Guinea, Liberia and Nigeria.
Ebola is spread through direct contact with the bodily fluids of an infected person.
Symptoms include fever, muscle aches, red eyes, diarrhea, vomiting and bleeding.