Nigerian authorities said they have confirmed a second case of Ebola in the country.

Nigerian Health Minister Onyebuchi Chukwu said on Monday that the second person with Ebola is a doctor, who had helped treat Patrick Sawyer, the Liberian-American man, who died of Ebola in late July.

Mr. Sawyer, who was travelling to Nigeria on business, became ill while aboard a flight and Nigerian authorities immediately took him into isolation. They did not quarantine his fellow passengers, and have insisted that the risk of additional cases was minimal.

Nigeria is the fourth country to report Ebola cases and at least 728 other people have died in Guinea, Sierra Leone and Liberia.