Up to 10,000 new people per week could be infected with Ebola if containment efforts aren't ramped up, international health officials warned.
That projection is much higher than the current estimate of Ebola cases released Tuesday: 8,914 patients.
World Health Organization officials said the death toll from Ebola has hit 4,447.
"A lot more people will die" without increased efforts to combat Ebola, said Dr. Bruce Aylward, assistant director-general of WHO.
Shortly after he spoke, Facebook founder Mark Zuckerberg revealed that he had donated $25 million as a grant to the Centers for Disease Control Foundation to help Ebola containment and treatment efforts.
Aylward said Ebola is now affecting more districts, counties and prefectures in the three countries where the outbreak is centered: Liberia, Sierra Leone and Guinea. Officials also said that the disease, in a troubling sign, is spreading to areas near the borders of those countries, raising the possibility that the virus will start affecting other nations on a larger scale.
WHO's projection of 10,000 new cases per week represents a tenfold increase in the current rate.
"We will go over 9,000 cases this week," Aylward said.
The mortality rate of the current Ebola outbreak-the largest since the virus was discovered in the mid-1970s-is 70 percent, officials said.
A clinic in Leipzig, Germany, on Thursday confirmed that a 56-year-old male U.N. worker stricken with Ebola after working in Liberia had died , four days after being transferred to Germany.
In a Dallas hospital, a 26-year-old nurse, Nina Pham, continued receiving treatment for Ebola, which she contracted while taking care of Thomas Eric Duncan. A Liberian national, Duncan, who died last week, contracted Ebola in his native country, but only showed symptoms of it late last month as he visited relatives in Dallas.
Pham is the first person known to have contracted Ebola in the United States, and her infection set off an intense, ongoing re-evaluation of how health-care workers are treating Ebola patients, and protocols they are using to prevent contracting the virus themselves. It is still unknown how Pham contracted the virus at Texas Health Presbyterian Hospital, where she is being treated.
Medical records obtained by the Associated Press show that about 70 health-care workers, including Pham, were involved in caring for Duncan. But it is not clear how many of those people are being monitored or will be. Officials previously had identified 48 people who had contact or possible contact with Duncan, all of whom were also being monitored.
As part of her treatment Pham has received a plasma transfusion from Dr. Kent Brantly , who survived the virus after treatment recently. Brantly had previously donated blood to Dr. Rick Sacra, who survived the virus, as well as to Ashoka Mukpo, a freelance NBC News cameraman who is undergoing treatment for Ebola in a Nebraska hospital.
That blood-based treatment is based on the theory that Ebola antibodies in Brantly's blood will help others combat the virus in their own bodies.
In a statement released by Texas Health Presbyterian on Tuesday, Pham said, "I'm doing well and want to thank everyone for their kind wishes and prayers. I am blessed by the support of family and friends and am blessed to be cared for by the best team of doctors and nurses in the world here at Texas Health Presbyterian Hospital Dallas."
In Kansas City, Kansas, a hospital is testing a man for Ebola after he went to the hospital Monday with a fever. The man recently served as a medical officer on a commercial ship off the coast of Africa. Officials said the man is "at low to moderate risk of Ebola."
In Sierra Leone, an entire battalion of 800 soldiers from that nation was placed in quarantine after one of them tested positive for Ebola. The battalion had been scheduled to soon travel to Somalia to relieve a group of peacekeepers there.