The confirmation that a fourth doctor had been infected comes as fear and anger about the dead being left unburied in Liberia's capital Monrovia brought protestors into the streets, while Sierra Leone's president said Monday that the epidemic threatened the "very essence" of the nation.
"This new case is one of the doctors who attended to the Liberian Ebola patient who died," Nigeria's Health Minister Onyebuchi Chukwu told journalists.
He said that 70 other people believed to have come into contact with the Liberian government official were being monitored.
Of the eight now in quarantine, three show "symptomatic" signs of the disease, he said.
More worrying still are reports from Liberia that victims' corpses were being dumped or abandoned. Protesters, who blocked major roads in the capital on Monday, claim that the government is not collecting bodies of victims left to rot in the streets or in their homes.
According to an update Monday by the UN World Health Organization, at least 887 people have died from Ebola since the beginning of the year as the virus has spread across Guinea, Liberia and Sierra Leone.
The Liberian government had warned against touching the dead or anyone ill with Ebola-like symptoms, which include fever, vomiting, severe headaches and muscular pain and, in the final stages, profuse bleeding.
"Four people died in this community. Because the government says that we should not touch bodies, no one has gone to bury them," Kamara Fofana, 56, a protestor in the Monrovia suburb of Douala, told AFP. "We have been calling the ministry of health hotline to no avail."
Miatta Myers said her mother was one of the suspected victims. "Our mother was vomiting. We tried to call the ministry of health but we did not see anyone. For five days now her body has been in the house. The only way we can get the attention of the government is to block the road."
Roadblocks first sprang up across major routes at the weekend and have appeared in several Monrovia neighbourhoods since.
Deputy health minister Tolbert Nyensuah said the government was doing its best to collect bodies as quickly as possible.
- Mass grave -
"We buried 30 people during the weekend in a mass grave outside the city. The government has purchased land from a private citizen and that land will be used to bury bodies," he said.
In neighbouring Sierra Leone, President Ernest Bai Koroma called for the nation to unite to counter the threat posed by the outbreak. "This is a collective fight. The very essence of our nation is at stake," he said in a televised address.
Streets in the capital Freetown were empty on Monday as people observed an emergency "stay at home day" called by the authorities to help them reorganise their fight against epidemic.
Sierra Leone has the most confirmed cases of any nation -- 574 -- including 252 deaths since the virus spread from neighbouring Guinea in May.
President Koroma, who declared a state of emergency last week, urged families to ensure that victims were reported to health authorities.
The doctor who has become the latest victim in Nigeria had treated Patrick Sawyer, who worked for Liberia's finance ministry, and who contracted the virus from his sister before travelling to Lagos for a meeting of west African officials.
He landed in Lagos on July 20 from Monrovia after switching planes in Togo's capital Lome.
He was visibly sick upon arrival and taken directly to the First Consultants hospital in the upmarket Lagos neighbourhood of Ikoyi. He died in quarantine on July 25.
The hospital was closed indefinitely last week.
Meanwhile, Kent Brantly, the US doctor infected with the virus, "seems to be improving", the director of the Atlanta-based Centers for Disease Control, where he is being treated in an isolation unit, said on Sunday.
A second American infected with the virus while working in Liberia is due to arrive back in the United States on Tuesday.
The Christian missionary group SIM USA said Nancy Writebol, 60, was in a "serious but stable condition" and was "expected to return to the US for further treatment on Tuesday".
She will be evacuated on the same plane that carried Dr Brantly, and will also be taken to the unit in Atlanta.