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.