The health of Ebola-stricken Spanish nurse Teresa Romero Ramos worsened on Thursday, and two doctors who treated her were admitted to a hospital for observation.
The BBC reported that Ramos "was being helped with her breathing in hospital."
Ramos, who became the first case of Ebola transmission outside of Africa, has been hospitalized since Sunday. Tests confirmed Monday that the sanitary technician had contracted Ebola, but Ramos said she only learned of her diagnosis from a media report -- though she sensed something was wrong when doctors stopped entering her hospital room.
It remains unclear exactly how she became infected while treating a priest who had contracted the virus in West Africa, though Ramos acknowledged this week that she may have made a mistake when removing her protective suit.
One of the doctors who treated her, Juan Manuel Parra, said in a statement posted to the El Pais Web site that the sleeves on the protective suit he wore while working with Ramos were too short.
According to the statement, Parra said he entered her room more than 12 times.
Parra treated Ramos at the Alcorcon hospital, near where the nurse lives in Madrid. She was later transferred to the Carlos III facility where she worked -- the same hospital that treated two missionaries who were repatriated after becoming infected in Africa.
Like Ramos herself, Parra said in his statement that he found out "from the media" that the patient had tested positive.
On Wednesday, Ramos told a Spanish newspaper that "the error was the removal of the suit," referring to the protective equipment health-care workers wear while treating Ebola patients. Earlier, she had said that she had "no idea" how she contracted the deadly virus.
Ramos became infected while treating Manuel Garcia Viejo, a priest who contracted Ebola in West Africa. She entered Viejo's room only twice, once to change his diaper, and a second time to remove his belongings after he died on Sept. 25.
Ramos began experiencing Ebola-like symptoms on Sept. 29, but was not admitted to a hospital under isolation until October 6, according to the World Health Organization's Thursday statement on the case.
The WHO added that " the healthcare worker was considered a low risk contact and monitored accordingly" before she became symptomatic. Spanish health officials "are conducting an investigation to elucidate the mode of transmission," the WHO said.
Ebola spreads from person to person through direct contact with the bodily fluids of an infected person.
German Ramirez, a doctor in the Carlos III Hospital's tropical diseases division, told reporters Wednesday that the nurse "has told us of the possibility that her suit had contact with her face. ... It could have been an accident. It looks like it was the gloves."
In addition to Ramos and the two doctors who treated her, several other people are under observation in Spain, including her husband, Javier Limón.
One Spanish man who had recently traveled to Nigeria and a nursing aide both tested negative for the virus. A third nursing aide and a nurse were hospitalized with slight fevers on Tuesday night, according to the Wall Street Journal.
Roberto Ferdman contributed reporting.
[This post has been updated]