(CNN) -- The number of deaths attributed to the current Ebola outbreak has topped 4,000, the World Health Organization reported Friday.
The latest count brings the total number of confirmed, probable, and suspected cases of Ebola to 8,399 and the total number of deaths to 4,033.
The numbers were reported from Guinea, Liberia, Nigeria, Senegal, Sierra Leone, Spain and the United States.
But along with news of the rising death toll, some suspected Ebola cases around the world -- from the United States to France -- have turned out to be false.
Concerns about protective measures, especially for those caring for the infected, remain high.
A total of 416 health care workers are among those believed to have contracted Ebola. Of those, 233 of have died, the WHO says.
'We just don't really know'
An American aid worker who contracted Ebola in Liberia and overcame the virus was said to have become infected while treating Ebola patients there, but she told CNN on Friday that there is no way to be sure.
Nancy Writebol was working with Samaritan's Purse in Liberia, caring for Ebola patients, when she became ill and was eventually transferred to an Atlanta hospital, where she recovered.
The belief has been that she contracted Ebola while working in a clinic with infected patients, but the survivor said that isn't necessarily the point of infection.
"Well, it's very possible that I contracted Ebola outside of the (medical) unit, not within," Writebol said. "Of course, I came in contact with people outside of our hospital, and I remember knowing and being with a gentleman one time that later died of Ebola. And it's possible that there was, you know, some contact there. We just don't really know."
Writebol was released from Emory University Hospital on August 19, once doctors determined she posed "no public health threat."
Her recovery has been gradual, Writebol said, but she is gaining strength each day.
The lack of clarity about where she became infected is significant as questions are raised worldwide about safety precautions at hospitals and communities as the outbreak stokes fears.
On Thursday, a test to see whether a Dallas sheriff's deputy had Ebola came back negative, state health officials said.
Word of the test result was welcome news a day after the death of Thomas Eric Duncan, the Texas Ebola patient who was the first person diagnosed with the virus on American soil.
The deputy had reported being inside the Dallas apartment where Duncan had been staying and having "some contact" with Duncan's family members, Frisco Fire Chief Mark Piland told reporters.
Ebola spreads through infected bodily fluids.
Spain creates a committee
In Spain, where a nurse's assistant was confirmed to have Ebola, authorities are taking measures to tackle the crisis.
The Spanish government will create a special committee to examine the issue, Deputy Prime Minister Soraya Saenz de Santamaria told reporters Friday in Madrid.
The committee, which will include representatives from government and health care, will coordinate national efforts to control the virus and establish protocols to deal with it, she said.
The nurse's assistant, Teresa Romero, is the first person to contract Ebola outside of West Africa.
A nurses' union spokesman told CNN that "some nurses and other workers from the Carlos III Hospital (where Romero is being treated) are taking leave for psychological reasons."
To cover those jobs, the Spanish health service is "making short term contracts hiring nurses that might be unemployed."
Spanish Prime Minister Mariano Rajoy visited Carlos III Hospital.
"The situation isn't a normal situation," he said. "It is difficult, but I'm absolutely convinced that everything necessary will be done, especially from the professionals, to overcome this in the future."
CNN's Al Goodman, Elwyn Lopez, Jason Hanna, Catherine E. Shoichet and Ashley Fantz contributed to this report.