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.
Ebola virus disease (EVD)
- Symptoms include high fever, bleeding and central nervous system damage
- Spread by bodily fluids such as blood, sweat and saliva
- Fatality rate can reach 90% - but current outbreak has mortality rate of about 70%
- Incubation period is two to 21 days
- There is no proven vaccine or cure
- Supportive care such as rehydrating patients who have diarrhoea and vomiting can help recovery
- Fruit bats, a delicacy for some West Africans, are considered to be natural host of virus
Protective Ebola suit×
The cap forms part of a protective hood covering the head and neck. It offers medical workers an added layer of protection, ensuring that they cannot touch any part of their face whilst in the treatment centre.
Goggles, or eye visors, are used to provide cover to the eyes, protecting them from splashes. The goggles are sprayed with an anti-fogging solution before being worn. On October 21, the US Centers for Disease Control and Prevention (CDC) announced stringent new guidelines for healthcare personnel who may be dealing with Ebola patients. In the new guidelines, health workers are advised to use a single use disposable full face shield as goggles may not provide complete skin coverage.
Covers the mouth to protect from sprays of blood or body fluids from patients. When wearing a respirator, the medical worker must tear this outer mask to allow the respirator through.
A respirator is worn to protect the wearer from a patient's coughs. According to guidelines from the medical charity Medecins Sans Frontieres (MSF), the respirator should be put on second, right after donning the overalls.
A surgical scrub suit, durable hospital clothing that absorbs liquid and is easily cleaned, is worn as a baselayer underneath the overalls. It is normally tucked into rubber boots to ensure no skin is exposed.
The overalls are placed on top of the scrubs. These suits are similar to hazardous material (hazmat) suits worn in toxic environments. The team member supervising the process should check that the equipment is not damaged.
A minimum two sets of gloves are required, covering the suit cuff. When putting on the gloves, care must be taken to ensure that no skin is exposed and that they are worn in such a way that any fluid on the sleeve will run off the suit and glove. Medical workers must change gloves between patients, performing thorough hand hygiene before donning a new pair. Heavy duty gloves are used whenever workers need to handle infectious waste.
A waterproof apron is placed on top of the overalls as a final layer of protective clothing.
Ebola health workers typically wear rubber boots, with the scrubs tucked into the footwear. If boots are unavailable, workers must wear closed, puncture and fluid-resistant shoes.