CONAKRY, Guinea (AP) — Doctors Without Borders insisted Friday, after one of its doctors who worked in Guinea came down with Ebola in New York City, that self-quarantines are not necessary when there are no symptoms of the disease.

Craig Spencer arrived back in New York about a week ago, reported a fever on Thursday and is now being treated at a New York hospital. Some countries have banned travelers from the three main Ebola countries — Guinea, Liberia and Sierra Leone — and the U.S. started health screening of travelers arriving from there.

In a statement sent to The Associated Press from Dakar, Senegal, Doctors Without Borders said that having its staffers quarantine themselves after leaving a country with Ebola is going too far if no symptoms are evident. A person infected with Ebola is not contagious until he or she starts showing symptoms.

"As long as a returned staff member does not experience any symptoms, normal life can proceed," said the group, also known by its initials in French as MSF. "Self-quarantine is neither warranted nor recommended when a person is not displaying Ebola-like symptoms."

Despite stringent infection-control measures, the risk of Ebola's spread cannot be entirely eliminated, Doctors Without Borders also emphasized. The group has been at the forefront in the battle against the disease. Ebola has infected roughly 10,000 people and killed about half of them, according to conservative estimates.

"Contagion is everywhere. Even in Conakry, the risk isn't zero," said an official in Guinea for Doctors Without Borders, referring to Guinea's capital. "But MSF takes measures to secure its personnel."

She refused to say where Spencer had been working in Guinea. The official spoke on condition of anonymity because of the sensitivity of the situation. Doctors Without Borders runs two treatment centers in Guinea: one in Gueckedou, in the southeast where the outbreak began, and the other in Conakry. It also runs a center near Gueckedou where patients are screened for Ebola and then sent for treatment if they have the disease.

The West African nation of Mali reported its first confirmed case of Ebola late Thursday, another example of how the disease can jump borders despite increased health checks at land borders, airports and seaports. A 2-year-old girl who came to Mali from Guinea was the confirmed Ebola case. Malian authorities are now monitoring 43 people, including 10 health workers, said Fadela Chaib, a spokeswoman for the World Health Organization in Geneva. The organization is sending experts to the country to help assess the situation.

MSF tells health workers who are returning home after a tour of duty that they must stay within four hours of a hospital with isolation facilities. It asks them to take their temperature twice a day and to be vigilant for symptoms, which include a fever.

The group said Spencer followed these procedures and immediately notified MSF when he came down with a fever.

The group discourages staff returning from West Africa from going back to work before the incubation period is up, so they can recover from the grueling work in the field and also so they don't pick up an infection while at work whose symptoms may look like Ebola, causing unnecessary anxiety.

More than 440 health care workers have been sickened in this outbreak, and more than half of those have died, according to the World Health Organization. That has strained already weak health systems in the worst affected countries, which had too few doctors and nurses to begin with and have had trouble convincing health workers to stay on wards at considerable risk to themselves and their families.

Liberia has offered its health workers hazard pay to treat Ebola patients, and Guinea has called on retired doctors to come back to work. Now, Guinea says it is giving $10,000 to the family of any health worker who has died from the disease, according to Dr. Sakoba Keita, the country's Ebola response coordinator. So far, 10 families have received the money — an enormous sum in Guinea, where doctors earn about $140 per month. Forty-one health workers in Guinea have died of the disease, according to WHO.

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DiLorenzo reported from Dakar, Senegal. Associated Press writers Jonathan Paye-Layleh in Monrovia, Liberia, and John Heilprin in Geneva contributed to this report.