A Spanish nurse who treated an Ebola patient in Madrid is thought to be the first person to have contracted the virus outside Africa.

Health Minister Ana Mato told a news conference that an emergency protocol had been put in place and authorities were working to establish the source of the contagion.

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The nurse treated elderly priest Manuel Garcia Viejo at the Carlos III hospital in Madrid last month when he was repatriated from Sierra Leone with the virus.

Mr Viejo died days later on August 12, the second Spanish priest to die after arriving from Africa with the disease.

Another Spanish missionary, Manuel Garcia Viejo was repatriated from Sierra Leone and died at the hospital on September 25.

Both were members of the Hospital Order of San Juan de Dios, a Catholic group that runs a charity working with Ebola victims in Africa.

Spanish health officials said they were monitoring 30 other health workers who attended the priests.

Hospital officials said people who had come into contact with the nurse were being monitored, although they had no knowledge of any further cases at present.

They said the nurse began to feel sick on September 30.

The deadly Ebola haemorrhagic fever virus has killed more than 3,400 people since it began in West Africa in March and has now started to spread faster, infecting almost 7,200 people so far.

In recent weeks it has spread to Nigeria, Senegal and the United States – where the first case was diagnosed last week – by unwitting travellers carrying the virus.