Nigerian authorities have confirmed a second case of Ebola in the country.
The second person who contracted the virus is a doctor who helped Patrick Sawyer, a Liberian-American man who died of Ebola in a Lagos hospital in July.
"Three others who participated in that treatment, who are currently symptomatic, have had their samples taken and hopefully by the end of today we should have the results of their tests," health minister Onyebuchi Chukwu said.
Nigeria is the fourth country in West Africa to be affected by Ebola, a deadly virus for which there is no cure.
The virus first appeared in Liberia in January, has also struck Sierra Leone and Guinea.
At least 728 people have died so far during the outbreak.
As the plane Sawyer was travelling in has not been quarantined fears are growing that virus could spread worldwide.
Meanwhile, Dr Kent Brantly, an American doctor who had contracted the virus while in Liberia, has been repatriated. His colleague, aid worker Nancy Writebol, who also showed symptoms of Ebola, is due to reach the US later this week.
Humanitarian organisation Doctors Without Borders (MSF) has deployed around 300 staff in West Africa to treat patients affected by Ebola. It has warned the outbreak is out of control, and curbing it will require "a massive deployment of resources by governments in West Africa and aid organisations".
Experts believe the virus could increase terrorist threats worldwide.
According to Peter Walsh, a biological anthropologist from Cambridge University, there is a "serious risk that a group manages to harness the virus as a powder, then explodes it in a bomb in a highly populated public area. It could cause a large number of horrific deaths".