A doctor in Madrid says the Spanish nurse infected with Ebola remembers touching her face with her gloves after treating a dying priest.
The nurse, Teresa Romero, is the first person known to have contracted the deadly virus outside West Africa.
She had treated two Spanish missionaries who later died from Ebola.
A World Health Organization (WHO) adviser has warned that more Ebola cases can be expected among medical staff, even in developed countries.
Ms Romero, a 40-year-old auxiliary nurse, remains in quarantine in the Spanish capital along with her husband and three other people.
A fifth person, said to be a friend and colleague of Ms Romero, was admitted on Wednesday morning with a slight fever. In all, more than 50 people in Spain are under observation.
The infected nurse was part of a team of about 30 staff at the Carlos III hospital in Madrid looking after the missionaries when they were repatriated from West Africa.
Miguel Pajares, 75, died on 12 August after contracting the virus in Liberia, while Manuel Garcia Viejo, 69, died on 25 September after catching the disease in Sierra Leone.
New figures released by the WHO show that more than 8,000 people have now been infected with the disease and 3,879 have died. The vast majority of deaths have been in Guinea, Sierra Leone and Liberia.
Nurse ‘doing better’
Ms Romero told the El Pais newspaper that she might have become infected when removing her protective suit after cleaning Mr Garcia Viejo’s room.
“I think the error was the removal of the suit,” she told El Pais by phone. “I can see the moment it may have happened, but I’m not sure about it.”
She added that she did not have a fever on Wednesday and was “doing better”.
In another development, the woman’s husband, Javier Limon, is reported to be fighting a court order to have their pet dog put down over fears it could be carrying the disease. Animal rights groups have also criticised the move, saying there is no evidence Ebola has been spread by dogs.
In other developments:
- First person to be diagnosed with Ebola within the US has died, Texas hospital confirms
- The US will begin screening passengers from affected countries as soon as this weekend
- The UK is sending 750 troops to Sierra Leone to help build Ebola treatment centre
- The World Bank has warned that the economic cost of the virus could exceed $32bn (£20bn)
Meanwhile, the head of Medecins Sans Frontieres (MSF) in Sierra Leone says the rest of the world is not doing enough to combat the outbreak of the Ebola virus.
Cristina Falconi, MSF’s chief in Sierra Leone, told the BBC that more staff, supplies and facilities were needed immediately to have any chance of halting the spread of the disease in West Africa.
“We need people, more people on the ground, more means of transport, more facilities, more beds. But also good management of these facilities,” Ms Falconi told the BBC’s Tulip Mazumdar.
In Sierra Leone, burial workers have gone on strike this week, leaving the bodies of Ebola victims on the streets of the capital, Freetown.
Local media said the teams had abandoned their posts in anger over unpaid wages, but Deputy Health Minister Madina Rahman insisted on Wednesday that the strike had been “resolved” and the staff would soon return to work.
The BBC’s Umaru Fofana in Sierra Leone says burial teams in the eastern district of Kenema remain on strike, saying they are owed four weeks’ wages by the government.
In neighbouring Liberia, health workers say they will go on strike if their demands for more money and safety equipment are not met by the end of the week.