An American doctor working with Ebola patients in Liberia has tested positive for the deadly virus.
Dr. Kent Brantly works for the U.S.-based Samaritan's Purse aid agency, which says he is being treated at a Monrovia hospital.
In Sierra Leone, health officials said an Ebola patient, whose family sparked a nationwide hunt when they forcefully removed her from a treatment center and took her to a traditional healer, died in an ambulance on the way to a hospital.
Health officials said fear and mistrust of health workers in Sierra Leone, where many people have more faith in traditional medicine, were hurting efforts to contain the Ebola outbreak.
The highly contagious Ebola virus has killed at least 672 people in four African countries since the outbreak began earlier this year.
Nigeria stepping surveillance
Meanwhile, Nigeria has stepped up surveillance at its ports and borders, following the country's first confirmed death from the Ebola virus.
Health Minister Onyebuchi Chukwu said health officials were monitoring airports, seaports and land borders for people arriving who may show signs of the virus. Officials confirmed Friday that a man, who died after arriving in Lagos on a flight from Liberia, had tested positive for Ebola.
Chukwu also said investigators were trying to track down the other passengers who were on the nearly three-hour flight from Monrovia.
Nigeria is the fourth West African country to confirm the presence of Ebola. The majority of deaths are in Guinea. In a report updated on Friday, WHO said 319 people had died from Ebola in Guinea. The health organization reported 224 deaths in Sierra Leone and 129 in Liberia.
There is no cure or vaccine for Ebola, which causes symptoms that include fever, vomiting, diarrhea and bleeding.
Some information for this report was provided by AP and Reuters.