The Spanish nurse who contracted Ebola in Madrid, a case that caused alarm and political recriminations, said on Wednesday she hoped her infection could be of use and offered to give blood to treat potential sufferers as she left hospital.

Teresa Romero, 44, overcame the deadly virus after becoming the first known person to catch Ebola outside West Africa in the current outbreak, which has so far killed nearly 5,000 people.

The contagion, after Romero cared for two priests repatriated from West Africa and who later died in Madrid, caused a backlash against the Spanish government, with health workers claiming they had received inadequate training and equipment to deal with Ebola.

"I don't know what went wrong, I don't even know if anything went wrong," an emotional Romero told a news conference, referring to the source of the contagion, which is still being investigated.

"I only know that I am not reproachful or resentful, but if my infection can be of some use, so that the disease can be studied better or to help find a vaccine or to cure other people, here I am," Romero said, accompanied by staff from the Carlos III Hospital where she was treated, and her husband.

Romero was given antibodies from a missionary nun who had caught Ebola in Liberia and who had also survived, as well as an experimental drug called favipiravir, doctors said. They added it was not clear exactly which part of the treatment had been key to her recovery.

Favipiravir, or Avigan, is made by Japan's Fujifilm subsidiary Toyama Chemical Co.

All of the people who had come into close contact with Romero before she was diagnosed, and were being monitored for signs of the disease in hospital, have now been declared free of Ebola. These included Romero's husband.

The couple's dog, Excalibur, was put down last month by Madrid authorities on fears it might pose an infection risk, prompting a public outcry.

The Carlos III Hospital said medical staff who attended Romero and room cleaners would now be monitored remotely for Ebola symptoms, by checking their temperature regularly until the end of the month. A fever is one of the symptoms of the disease, which can also cause bleeding, vomiting and diarrhea.

It is spread through direct contact with bodily fluids of an infected person.

Nursing staff who helped treat Romero said on Wednesday they had felt stigmatized by the disease and had suffered rejection from friends and neighbors, while hospital officials tried to reassure the public that there was no longer any risk of Romero being contagious.