The World Health Organization expressed worry on Wednesday about a second cluster of Ebola virus patients in Nigeria — in the center of its oil industry — because one of the three confirmed victims was a doctor who had treated patients and socialized after he became contagious.
The doctor, in the southern city of Port Harcourt, died on Aug. 22, and his infection was confirmed five days later. On its website, the W.H.O. said that more than 200 people might be at risk.
The W.H.O. said this second cluster had indirectly resulted from a quarantine lapse in the first cluster of Ebola cases that hit Lagos, Nigeria’s largest city, in July, and was potentially far more serious. Tracing the spread of the disease in Port Harcourt, the statement said, revealed “multiple high-risk opportunities for transmission of the virus to others.”
Ebola has primarily afflicted three countries in West Africa — Guinea, Liberia and Sierra Leone — where hundreds of people have died in recent weeks in what W.H.O. officials have called the worst outbreak of the disease ever recorded. While the toll in Nigeria has been far more limited, officials are particularly worried about it because it is Africa’s most populous country.
The W.H.O. has been criticized by some other medical advocates for what they call its initial failure to mobilize adequately against Ebola when the outbreak surfaced in West Africa months ago.
The Lagos cases were traced to a traveler from Liberia, and Nigerian officials thought they had basically contained the spread. But the health organization’s statement said one person in Lagos escaped a quarantine in early August and sought treatment from a doctor in Port Harcourt, nearly 400 miles away. That doctor became infected and developed symptoms after a few days, was hospitalized on Aug. 16 and died of Ebola less than a week later.
Even as he developed symptoms, the statement said, the doctor “continued to treat patients at his private clinic, and operated on at least two.” Moreover, the statement said, before he was hospitalized the doctor “had numerous contacts with the community, as relatives and friends visited his home to celebrate the birth of a baby.”
The other two confirmed cases in Port Harcourt are the dead doctor’s wife, who is also a doctor, and another patient at the same hospital. The W.H.O. statement said that epidemiologists were monitoring “more than 200 contacts” and that 60 were considered especially vulnerable.
It said the Ebola outbreak in Port Harcourt had “the potential to grow larger and spread faster than the one in Lagos.”
Discovered in 1976, Ebola is an aggressive virus that causes high fevers, extreme weakness and internal bleeding, with a fatality rate as high as 90 percent.
In Washington, the head of the W.H.O., Dr. Margaret Chan, said Wednesday at a news conference that there had been at least 3,500 Ebola cases, with more than 1,900 deaths. She called the outbreak “the largest and most severe and most complex we’ve ever seen in the nearly 40-year history of this disease.”
Last week, the organization, based in Geneva, said Ebola could afflict more than 20,000 people before it was brought under control.