The health of a Spanish nurse with Ebola worsened on Thursday and four other people were put into isolation in Madrid, while the country's government rejected claims its methods for dealing with the disease weren't working and blamed human error.

Teresa Romero, 44, is the first person to have contracted Ebola outside of Africa, after becoming infected by a Spanish priest repatriated from Africa with the disease.

In total seven people are in isolation, though only Romero has tested positive for Ebola. The others include the nurse's husband and two doctors who cared for her. Three other people were released from the isolation unit late on Wednesday after testing negative.

A health official at the Carlos III Hospital where Romero is being treated said on Thursday: "Her clinical situation has deteriorated but I can't give any more information due to the express wishes of the patient."

The European Commission asked for an explanation of how Romero's infection happened in a high-security ward.

"It's obvious that the patient herself has recognized that she did not strictly follow the protocol," Ruben Moreno, spokesman for health for the ruling People's Party, said in a television interview.

German Ramirez, one of the doctors at the hospital where Romero is being treated, said on Wednesday she had told him she touched her face with her protective gloves.

On Thursday another doctor, who cared for Romero and is among those now in isolation, said the sleeves on the protective suit he wore while handling her had been too short.

In a letter to healthcare authorities, published by national newspaper El Pais, the doctor detailed treating Romero during a grueling 16-hour shift during which he was not told she had the Ebola virus. He said he only learned of this via the press.

The Ebola virus has killed nearly 4,000 people in West Africa since March in the largest outbreak on record. It causes hemorrhagic fever and is spread through direct contact with body fluids from an infected person.

The World Health Organization has said it sees no evidence of the disease being brought under control in Liberia, Sierra Leone and Guinea. The first person diagnosed with Ebola in the United States died on Wednesday and the U.S. government ordered extra screenings at five major airports.

CALLS FOR CALM

In Madrid, health workers at a major hospital protested about inadequate training to deal with the virus while unions have demanded the resignation of Health Minister Ana Mato.

A union official said training for staff to deal with expected Ebola cases was inadequate. "In some places they are carrying out drills, in others not, there is a lack of co-ordination," union official Rosa Cuadrado told Reuters.

News of the contraction of the Ebola virus in the country has deeply shaken Spaniards' faith in their government and the health system, which has suffered deep spending cuts as part of austerity measures over the past years.

While newspapers run columns and diagrams on the life-cycle of the virus, Prime Minister Mariano Rajoy has called for calm and said an outbreak affecting many people was extremely unlikely.

His party's health spokesman said Spain had not relaxed protocol in dealing with the disease but there may have been human error.

Peter Piot, a professor at the London School of Tropical Medicine who was one of the discoverers of the Ebola virus almost 40 years ago, told reporters in Geneva on Wednesday: "The smallest mistake can be fatal."

"For example, a dangerous moment is when you undress - you come out of the isolation unit, you take off your protective gear, you’re full of sweat and so on, and you take off your glasses and you do like this - " he said, rubbing his eyes - "and that can be the end."

The investigation into how Romero contracted the disease continues. The government health spokesman also said the ambulance that collected Romero from her home, while disinfected between trips, went on to carry other patients to hospital without being taken out of circulation until she was known to have contracted Ebola.

Patients carried in the ambulance were unlikely to have caught the disease as they did not have direct contact with the nurse, but were being monitored, the spokesman said. He could not say how many traveled in the ambulance, although press reports put it at seven patients.