A Spanish nurse has tested positive for Ebola weeks after she treated a patient who eventually died of the disease, in what may be the first case of virus' transmission outside Western Africa.

Ana Mato, Spain's health minister, said the nurse was part of a medical team that treated Manuel Garcia Viejo, a 69-year-old Spanish priest who died last month in Spain after contracting the virus while working in Sierra Leone.

"Two tests were done and the two were positive," a spokesman for the health department of Madrid told the AFP news agency on Monday. The nurse was now in isolation in a hospital on the outskirts of Madrid.

Journalist Miguel Anxo told Al Jazeera that the most of the health minister's press conference on Monday was devoted "to trying to calm fears of the disease spreading."

According to Anxo, although the nurse interacted with people freely before being aware of having the disease, "doctors have been clear that until you show symptoms of Ebola, it is supposed not to be contagious, and therefore the authorities are hoping the virus have not spread due to the short span of time since she has displayed symptoms." 

The Ebola outbreak in West Africa has killed at least 3,439 people since it began in March, out of nearly 7,500 confirmed, probable and suspected cases. Liberia, Sierra Leone and Guinea are the worst-hit countries.  

Meanwhile, the US administration has said it is not considering a ban on travellers from countries most affected by the virus.

"A travel ban is not something that we're currently considering," said Josh Earnest, a White House spokesman. "We feel good about the measures that are already in place."

Five US citizens have contracted the disease, four of whom contracted the disease while working in West Africa. The fifth was diagnosed with the disease in the US although it is unclear where the patient contracted the disease.