The World Health Organization declared on Monday that Nigeria is free of Ebola, a rare victory in the months-long battle against the fatal disease.
The disease continues to spread rapidly in Liberia, Sierra Leone and Guinea and has claimed more than 4,500 lives.
Nigeria's containment of the lethal disease is a "spectacular success story," WHO Country Director Rui Gama Vaz told a news conference in Abuja, Nigeria's capital. Nigeria reported 20 cases of Ebola, including eight deaths. One of those who died was an airline passenger who brought Ebola to Nigeria and died soon after.
The WHO announcement came after 42 days passed - twice the disease's maximum incubation period - since the last case in Nigeria tested negative.
"The outbreak in Nigeria has been contained," Vaz said. "But we must be clear that we only won a battle. The war will only end when West Africa is also declared free of Ebola."
WHO said Nigeria had traced nearly every contact of Ebola patients in the country, all of whom were linked to the country's first patient, a Liberian man who arrived with symptoms in Lagos and later died.
For an outbreak to be declared officially over, WHO convenes a committee on surveillance, epidemiology and lab testing to determine that all conditions have been met.
Vaz warned that Nigeria's geographical position and extensive borders makes the country, Africa's most populous, vulnerable to additional imported cases of Eebola.
"Therefore there is need to continue to work together with states to ensure adequate preparedness to rapidly respond, in case of any potential re-importation," he said.
The disease continues to spread rapidly in Liberia, Sierra Leone and Guinea and has claimed more than 4,500 lives.
Ebola monitoring eases for some in Dallas
Ebola fears began to ease for some Monday as a monitoring period passed for those who had close contact with a victim of the disease and after a cruise ship scare ended with the boat returning to port and a lab worker on board testing negative for the virus.
Federal officials meanwhile ramped up readiness to deal with future cases. A top government official said revised guidance instructs health workers treating Ebola patients to wear protective gear "with no skin showing." The Pentagon said it is forming a team to support civilian medical staff in the U.S.
In Dallas, Louise Troh and several friends and family members will finally be free Monday to leave a stranger's home where they have been confined under armed guard for 21 days - the maximum incubation period for Ebola. They had close contact with Thomas Eric Duncan, a Liberian man who died of the disease at Texas Health Presbyterian Hospital on Oct. 8.
"I want to breathe, I want to really grieve, I want privacy with my family," Troh told The Associated Press.
The incubation period also has passed for about a dozen health workers who encountered Duncan when he went to the Dallas hospital for the first time, on Sept. 25.
Duncan was sent home but returned by ambulance on Sept. 28 and was admitted. Two nurses who treated him during that second visit - Nina Pham and Amber Vinson - are now hospitalized with Ebola.
Vinson's family issued a statement Sunday saying they have hired a lawyer and are troubled by comments and media coverage that "mischaracterize" Vinson, who is being treated at Emory University in Atlanta. Vinson "has not and would not knowingly expose herself or anyone else," the statement says.
Dallas County and federal Centers for Disease Control and Prevention officials cleared her to fly last week to Dallas from Ohio, and "suggestions that she ignored any of the physician and government-provided protocols recommended to her are patently untrue and hurtful," the family says.
On Sunday, a Carnival Cruise Lines ship returned to Galveston, Texas, from a seven-day trip marred by worries over a health worker on board who was being monitored for Ebola. The lab supervisor had handled a specimen from Duncan and isolated herself on the ship as a precaution.
About 4,000 passengers on the cruise had to miss a stop in Cozumel, Mexico, where the boat was not allowed to dock because of the scare. Carnival said it was informed by U.S. health authorities Sunday morning that the worker tested negative for Ebola.
The CDC is working on revisions to safety protocols. Earlier ones, Fauci said, were based on a World Health Organization model for care in remote places, often outdoors, and without intensive training for health workers.