“This is a tragic, painful, dreadful, merciless virus. It’s the largest, most complex outbreak that we know of in history,” said CDC director Tom Frieden in a news briefing Thursday.

A patient who was infected with the virus in Africa is expected to be treated at Emory University Hospital in Atlanta within the next several days, the university said in a statement Thursday. The patient, his or her identity undisclosed, will be treated at a special containment unit set up in collaboration with the CDC to treat people exposed to serious infectious diseases. A spokeswoman said she did not know when the patient will arrive, or who the patient is.

Frieden warned that this outbreak will take at least 3 to 6 months to suppress, under the best of circumstances. There is no cure or treatment for the disease, in which the virus replicates rapidly throughout the body, causing multiple organ failure and, typically, death in a matter of days. In the latest outbreak, 6 of 10 people infected have died.