Spain has quarantined a total of four people in an attempt to prevent the spread of Ebola after a nurse became the first confirmed case of infection outside West Africa.

The 40-year-old nurse, her husband, another health worker and a Spaniard who travelled to Nigeria are in isolation in hospital, Madrid health officials said on Tuesday.

The husband shows no symptoms, and the health worker has diarrhoea but no fever. There was no information about the condition of the fourth person.

Rafael Perez-Santamaria, the head of the Carlos III Hospital, said a further 22 people who had been in with the nurse contact were being monitored.

The nurse had treated a 75-year-old Spanish missionary who had caught the disease in Liberia, and a 69-year-old priest who caught Ebola in Sierra Leone. Both missionaries died, the first on August 12 and the second on September 25.

The nurse fell ill on September 30, and officials said she entered the room of the second patient twice.

“This has taken us by surprise,” said Perez-Santamaria. “We are revising our protocols, improving them. The priority remains to find out what actually happened.”

The health ministry’s chief coordinator for health alerts and emergencies, Fernando Simon, told local radio that there was a small chance that people who had come into contact with the nurse may have contracted the disease.

A small number of public health workers demonstrated in Madrid over the infection, and the danger faced by hospital staff.

“This is not a game to be played in the way they have done. It is a very worrying matter and they have not handled it correctly,” a nursing assistant at Madrid’s La Paz hospital, which one of the missionaries had visited.

A cardiologist at the hospital added: “We cannot understand how someone who was wearing a double protection suit and two pairs of gloves could have been contaminated.” Al Jazeera