The World Health Organization is also considering medical evacuation for an international health worker who has become infected in Sierra Leone, the U.N. health agency said in a statement.
Neither patient was identified by name, and the nationality of the infected WHO employee was not given.
The British patient was working at an Ebola treatment center in eastern Sierra Leone, the region most affected by the outbreak, said Sidie Yayah Tunis, director of communications for the Sierra Leone health ministry.
The two cases highlight the risks facing health workers on the front lines of the battle against Ebola, which has killed more than 1,400 people across West Africa, according to the latest WHO figures.
"This is the first time someone working under the aegis of WHO has fallen ill with the disease," the WHO said in its statement, adding that more than 225 health workers have been infected and nearly 130 have died from Ebola during the current outbreak.
The British patient was transported via ambulance to Sierra Leone's main airport in the town of Lungi, Tunis said.
Britain's Department of Health said the patient was being flown on a specially equipped RAF transport plane to Northolt air base in London.
He will be treated at London's Royal Free Hospital, which has an isolation unit for infectious disease.
The department said in a statement that the patient "is not currently seriously unwell."
The World Health Organization says Sierra Leone has recorded 910 Ebola cases and 392 deaths. The Sierra Leone government says there have been 881 cases and 333 deaths. In Kenema, where the Briton was working, the government has recorded 303 cases.
A total of 2,615 infections and 1,427 deaths have been recorded in the Ebola outbreak now hitting West Africa, according to figures released Friday by the World Health Organization.
The Nigerian Medical Association said Sunday it has suspended a public sector doctors strike to help efforts to contain Ebola in the country.
The association also demanded the government restart a residency training program it suspended on Aug. 13.
Nigerian Health Minister Onyebuchi Chukwu had said earlier this month while the strike was putting Nigeria at a disadvantage, it hadn't affected the containment efforts. The government has been appealing to doctors to return to work to help contain the virus, and has been asking volunteers to join in the efforts, including contact tracing of people under surveillance.
Five people in Nigeria have died of the virus, while five recovered and were discharged from hospital, according to the government. The other four cases are receiving treatment in isolation in Lagos. As of Friday, the minister said 213 people, who were contacts of those who had tested positive for the virus, were under surveillance and are being monitored.
In Liberia on Saturday, hundreds of people lined up outside the capital's largest slum to bring food to relatives stuck inside after officials slapped a blockade on it this week. The slum, West Point, is home to at least 50,000 people. The government says the blockade is necessary to prevent the spread of Ebola but residents are worried about food shortages. They say rice distributed by the government has been insufficient and of poor quality.
Liberia has recorded 1,082 Ebola cases and 624 deaths, according to the WHO.
Two Americans and a Spanish medical worker have already been evacuated from Liberia and given ZMapp, an experimental and unproven treatment for Ebola. The Americans have recovered and been discharged while the Spaniard died.
The drug supply is now exhausted, the U.S. manufacturer has said.
The Philippine government said Sunday that it was preparing to carry out a mandatory evacuation of Filipinos in three West African countries due to the Ebola outbreak.
Department of Foreign Affairs spokesman Charles Jose said in Manila that there were 1,979 Filipinos in Sierra Leone, 880 in Guinea and 632 in Liberia, including 148 U.N. peacekeepers. Jose did not give a date but said the repatriation of the Filipino workers and their dependents would be carried out "very soon."
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