The Spanish nurse who became the first person to contract Ebola outside West Africa appears to have overcome the disease, officials said tonight.

Teresa Romero, 44, went into isolation after caring for two infected priests at Carlos III Hospital in central Madrid.

Her case prompted a massive public outcry of the Spanish government's handling of the outbreak, which blew up into mass protests when her beloved dog Excalibur was put down despite it being unclear whether the pet had the virus.

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Saved: Teresa Romero, 44, has tested negative for Ebola weeks after contracting the disease, the Spanish government said. But her dog Excalibur (pictured) was put down as a precaution, sparking a national outcry

Innocent: Some 390,000 animal rights activists and protesters called for Excalibur (pictured) to be spared

Death row: Excalibur barking on Ms Romero's Madrid balcony before the pet was put down by the authorities

Ms Romero's husband Javier Limon Romero (pictured with their dog) is being kept in quarantine in Madrid

Thousands of angry protesters marched in the streets of Madrid calling on the government's health minister Ana Mato to resign after the pet's death on October 8.

Ms Romero's recovery could prompt further criticism by the protesters, 390,000 of whom signed a petition urging officials to save Excalibur's life.

Although Ms Romero's recovery would not have changed the odds of Excalibur contracting the disease, protesters had insisted the animal could have been cared for safely in quarantine.

U.S. officials took just that tack when they announced they would be saving Bentley, the spaniel belonging to Ebola patient Nina Pham in Dallas, Texas.

Today Ms Romero tested negative for the disease, the government said in a statement. Further tests will be carried out tonight to confirm the result, as patients must be re-tested within 72 hours.

The nurse cared for Spanish missionary Manuel Garcia Viejo, 69, who died on September 25 after being infected with Ebola while he treated patients in Sierra Leone.

Another Spanish priest, 75-year-old Miguel Pajares, had died in Madrid in August after being flown back from missionary work in Liberia.

Anger: There was a mass demonstration in Madrid when Ms Romero's pet dog Excalibur was put down

Thousands of protesters in Madrid including health workers have called on the health minister to resign

Protests: One activist's dog wore a sign which said Excalibur's death could not be forgotten or forgiven

Ms Romero was treated with a drip of human serum containing antibodies from Ebola sufferers who had survived the disease, and other drugs which a government spokesman declined to name.

One was the experimental anti-viral medicine favipiravir, according to the respected national newspaper El Mundo.

Romero is the only known sufferer of Ebola in Spain after the death of the two priests.

But there are a further 15 people in hospital, including her husband, being kept under observation for signs of the disease.

Photographs of them appearing at a window holding up placards to declare they were in perfect health last week were beamed around the world.

'I'm fine': One of the 15 others being kept in quarantine showed his temperature from the hospital window

Protection: Health workers at the window of the Carlos III hospital in Madrid, where 15 people are being held

Wistful: Ms Romero's husband, still in quarantine, watches Spain's national day celebrations from the window

Ebola has killed at least 4,546 people in Liberia, Sierra Leone and Guinea in the recent outbreak.

So far only two countries, Spain and the U.S., have had fresh cases confirmed outside West Africa. In both cases they arose after contact with patients who had been flown home for treatment.

Outside the three main countries, there were also 20 fresh cases of Ebola in Nigeria and one in Senegal, where the World Health Organisation said the outbreak has been successfully contained.

Spain has given its permission for the United States to use U.S. military bases in an operation to send up to 4,000 troops to West Africa to help contain the disease.

The bases are at Rota near Cadiz and at Moron de la Frontera near Seville in southern Spain, the Ministry of Defence said in a statement on Saturday.

Other protests, including by health workers who wore symbolic white masks, have criticised the Spanish government's response to the outbreak.