Ebola:Threat Forced Lagos to Scramble.

A nurse Thursday places an information sign about Ebola on a wall of a public-health center in Monrovia, Liberia, which announced school closures. Agence France-Presse/Getty Images.

Doctors in Lagos, Nigeria, were on strike July 20, the day a man infected with Ebola landed at a packed airport in Africa's biggest city.

In a few days a Muslim holiday would send health workers on a break and millions of ordinary people crowding into buses and planes. The city's health commission was out of thermometers, said Health Commissioner Jide Idris.

In a press conference Friday, President Obama said the CDC and other U.S. health agencies are working with the World Health Organization to send a surge of resources to Africa to contain the Ebola outbreak.

It could have been a nightmare, but a chaotic overpopulated city showed how some organization and creative hustle can tamp down the threat of one of the world's deadliest viruses.

While nearby nations Liberia, Guinea and Sierra Leone have been struggling to tame an Ebola outbreak that has killed 729 people this year, Nigerian officials crash-trained lab technicians and civil servants on how to enter a house and check for the virus. In four days, they turned an abandoned government building into an isolation unit. In a week they managed to find and cold-call scores of people from blue-collar workers to diplomats who may have touched Patrick Sawyer, the Liberian-American passenger whose landing in Lagos could have sparked an outbreak in a city of as many as 21 million people.

Lagos also got lucky: Mr. Sawyer, a consultant at the Liberian Finance Ministry, collapsed on arrival in the city and was put in isolation at a hospital. Had he spent even a few hours outside the airport, he might have spread his illness to exponentially more people, many of them impossible to trace in the city's endless sprawl of tin-roof shacks and walk-up apartments.

More than 1,323 people have been sickened, about 60% of them fatally, in West Africa since Ebola erupted from the forested interior of Guinea, according to the World Health Organization. The hundreds dead include a top Sierra Leonean doctor and another from Liberia, while two U.S. health-care workers are ill.

The Centers for Disease Control and Prevention is part of a new international effort to help bring the ebola outbreak in Africa under control, as at least one American ebola patient is flown to Atlanta for care. WSJ's Betsy McKay discusses on Lunch Break.

On Friday, Guinea, Sierra Leone and Liberia agreed to quarantine the area where their countries share a border, said Liberian Information Minister Lewis Brown.

Also on Friday, WHO Director-General Margaret Chan said the outbreak is spreading faster than health workers can control it, yet it can be stopped with a well-managed response. She will lead an international response coordinated by the WHO, which on Thursday said it is launching a $100 million effort with its member states to bring the outbreak under control.

Dr. Chan put her finger on the problem that has allowed Ebola to spin out of control in West Africa, despite efforts by experts who have been able to tame outbreaks of the same disease for some 40 years elsewhere: "This is not just a medical or public-health problem," she said. "It is a social problem. Deep-seated beliefs and cultural practices are a significant cause of further spread and a significant barrier to rapid and effective containment."

Health workers have been up against doubts about Western medicine compounded by belief systems that encourage family members to care personally for their infected loved ones and to follow burial rites that have them handling still-contagious corpses. Mobs of angry and suspicious citizens have attacked teams of health workers. Families have hidden suspected cases, preferring to keep them at home rather than allow them to be taken to a treatment center and isolated.

A few weeks ago, staff members at one Ebola treatment center thought they had gotten through the worst when they were down to one convalescing patient, said Pierre Rollin, a veteran Ebola expert at the U.S. Centers for Disease Control and Prevention, who is currently in Guinea. Then one family that hadn't brought its sick for treatment sparked a resurgence, he said. The treatment center now has as many as 17 patients.

"Chains of transmission have moved underground. They are invisible. They are not being reported," Dr. Chan said. "Because of the high fatality rate, many people in affected areas associate isolation wards with a sure death sentence, and prefer to care for loved ones in homes or seek assistance from traditional healers."

At the same time, Ebola is so rare a disease that no more than 300 professionals globally have worked on outbreaks before, Dr. Rollin said: "We need more people."

Lagos, meanwhile, might not be out of the storm yet. There are still a small number of people who were on the flight with Mr. Sawyer that health workers haven't found, said Oluwakayode Oguntimehin, a permanent secretary on the Lagos State Primary Healthcare Board, who helped to lead the response. The next three days are a critical period when the virus is likely to flare and become contagious if those people have it.

What is clear, though is that hundreds more lives could have been saved if more West African governments acted as Lagos did.

When the government received the passenger list for Mr. Sawyer's flight, it was missing contact information for 18 of the flight's 48 passengers. All officials had to go by were names and their nationality—in a part of the world where phone books don't exist.

Liberian soldiers move through streets to prevent panic as fears of the deadly Ebola virus spread in the city of Monrovia, Liberia, on Friday. Associated Press

The airline tracked down some passengers by calling the ticket agents that booked the flight, and Nigeria's government found others by contacting local embassies. Again, they were lucky: The plane was full of government workers on their way to a conference, passengers who were easy for diplomats to track.

A crew of health workers set about cold-calling people with the terrifying news they might have Ebola. "Are you feeling feverish," was their opening question, said Dr. Oguntimehin. "You're trying to reassure them."

They sent nurses, lab technicians and civil servants into homes to deliver forms that potential carriers now fill out twice daily, asking about muscle aches, fever or nausea. By Friday, only two had developed a fever—the handlers who helped Mr. Sawyer into a wheelchair. Their blood tested negative, and they are still under close watch.