John Bacon and Liz Szabo

USA TODAY

New cases of Ebola could reach 10,000 per week by December as the virus outbreak races out of control in West Africa, World Health Organization officials said Tuesday.

WHO Assistant Director-General Bruce Aylward also said the death rate, which had been estimated at about half of those who become infected, has risen to about 70%.

Aylward said there have been about 1,000 new cases reported per week over the last month. He said WHO is aiming to isolate 70% of cases — and to have 70% of victims buried quickly and safely — within two months to reverse the outbreak.

"A lot more people will die" if the crisis response isn't stepped up within two months, Aylward said. He said WHO's goal is to begin seeing a week-to-week decline in the number of new cases in the Ebola hotbeds of Liberia, Guinea and Sierra Leone within 90 days.

The disease is expanding into more areas of those countries, Aylward said. But he stressed that overwhelmed treatment centers would not consider isolation without treatment.

"It would be horrifically unethical to suggest that we're simply going to isolate people," he said. New strategies such as handing out protective equipment to families and setting up very basic clinics is a priority, Aylward added.

As of Tuesday morning, 8,914 Ebola cases and 4,447 deaths had been reported to WHO. Aylward stressed that the true number of deaths and infections is probably much higher.

Federal health officials will rush dedicated Ebola teams to any U.S. hospital that confirms an Ebola case, Centers for Disease Control and Prevention director Thomas Frieden said Tuesday.

Frieden also said officials have thus far failed to determine how Dallas nurse Nina Pham contracted the virus during treatment of Thomas Eric Duncan, who died last week at Texas Health Presbyterian Hospital.

The 48 people who had contact with Duncan before he was hospitalized have reached 14 days without symptoms, Frieden said, meaning their likelihood of contracting the disease has lessened. About 76 health care workers had contact with Duncan or his blood while he was hospitalized, and all are being monitored closely.

Still, Frieden acknowledged at a news conference Tuesday that more CDC experts should have been sent more quickly to the Dallas hospital.

"We should have put an even larger team on the ground immediately, and we will do that any time there is a confirmed case," Frieden said.

The CDC has sent 20 staffers to Dallas. In the event of future outbreaks: "We will be there, hands on, within hours, to help the hospital deal with the situation."

Two nurses from the specialized biocontainment unit at Atlanta's Emory University Hospital are in Dallas to review the hospital's procedures. Frieden said the CDC is recommending that hospitals limit the number of people allowed into the Ebola unit and have a 24-hour site manager to oversee all aspects of the unit.

If necessary, Frieden said future Ebola patients could be transferred to one of the four hospitals in the USA with specialized biocontainment units. Two of them already have treated Ebola patients — at Emory and Omaha's Nebraska Medical Center.

Pham, 26, issued a brief statement through Texas Health Presbyterian saying she is "doing well" and thanking the medical team providing her care.

"I'm doing well and want to thank everyone for their kind wishes and prayers," the statement said. "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."

Texas Health Resources CEO Barclay Berdan also released a statement, saying the "hearts and prayers of everyone at Texas Health Presbyterian Hospital Dallas are with Nina Pham, and we are working tirelessly to help her in this courageous fight. The doctors and nurses involved with her treatment remain hopeful, and we ask for the prayers of the entire country."

Frieden said one person who had contact with Pham was being monitored but thus far is healthy.

Dallas Mayor Mike Rawlings also reported that Bentley, Pham's King Charles spaniel, was doing well and also showing no signs of the virus. The dog was moved to a secure, undisclosed location after Pham checked herself into the hospital.

"He's wagging his tail, eating, drinking water," he said. "Cute as a button."

Pham became infected while treating Duncan, the first Ebola patient to die in the USA. Pham, who graduated from Texas Christian University's nursing program in 2010, is the first person known to contract the disease in the USA.

She has received a transfusion of plasma from Kent Brantly, a Texas physician who survived the virus, according to the non-profit medical mission group Samaritan's Purse. Brantly's plasma should contain antibodies valuable in fighting the virus.

Also Tuesday:

• Facebook founder Mark Zuckerberg said that he and his wife, Priscilla, will donate $25 million to the U.S.-based Centers for Disease Control Foundation to help fight Ebola.

"The Ebola epidemic is at a critical turning point," Zuckerberg said in a Facebook post, adding that the couple believes the money will "directly help the front-line responders in their heroic work. These people are on the ground setting up care centers, training local staff, identifying Ebola cases and much more."

• In Germany, St. Georg Hospital in Leipzig announced that a 56-year-old United Nations staffer died early Tuesday of the disease "in spite of intensive medical care." He had tested positive Oct. 6.

Contributing: Rick Jervis