Four people, including the husband of a nurse who was diagnosed with Ebola, have been placed in quarantine over fears they may have the deadly virus.

The Madrid nurse who became the first person to contract ebola outside of Africa is being treated with antibodies from survivors of the illness, hospital officials have revealed.

Spain's health authorities say a total of 22 people are thought to have been in contact with the 40-year-old nurse, whose name has not been released but is in stable condition.

They say that although she began a holiday after one of the missionaries she had been caring for died on 25 September, she did not leave Madrid during this time.

Spanish officials say she began feeling ill on 30 September and was diagnosed with Ebola on Monday.

The woman works at Madrid's La Paz-Carlos III hospital where two missionaries died after being repatriated from Africa with the disease.

Health Minister Ana Mato said an emergency protocol had been put in place and authorities were working to establish the source of the contagion.

Spanish priest Miguel Pajares, 75, was infected with ebola in Liberia and died at the hospital on 12 August.

Another Spanish missionary, Manuel Garcia Viejo, 69, was repatriated from Sierra Leone and died at the hospital on 25 September.

A Spanish health official said 30 medical staff who treated the two priests are being monitored. Both were members of a Roman Catholic group that runs a charity working with ebola victims in Africa.

The nurse is said to have been admitted to hospital on Monday morning with a high fever.