Dozens of people are being monitored in Mali after the country confirmed its first case of Ebola.
WHO reinforcements
Mayor's assurance
Ebola virus disease (EVD)
Craig Spencer returned to New York from Guinea on 17 October
The patient is a two-year-old girl who recently arrived from Guinea, which along with Liberia and Sierra Leone has seen most of the 4,800 deaths.
However, the Malian health ministry says her condition is now improving.
The World Health Organization (WHO) has meanwhile announced that hundreds of thousands of vaccine doses should be available in the first half of 2015.
WHO Assistant Director Dr Marie-Paule Kieny told a news conference in Geneva that five more vaccines would be in the clinical trial stage in January. Two are already being tested on humans.
"The pharmaceutical companies developing these vaccines, as well as the ones which are a little bit further along the development path, are committing to ramping up the production capacity to millions of doses to be available in 2015 with hundreds of thousands ready in the first half of next year," she said.
Vaccine trials in the worst-affected countries could begin in December, Dr Kieny said.
In other developments:
- An international team of scientists has been set up to determine the effectiveness of using the blood of Ebola survivors as a treatment. It is hoped the antibodies used by the immune system to fight Ebola can be transferred from a survivor to a patient
- European Union leaders agreed to increase their financial help on fighting Ebola in West Africa from some 600 million euros ($758m; £743m) to one billion
The BBC's Gabriel Gatehouse travels with an ambulance worker in Liberia
Mali has now become the sixth West African country to be affected by the outbreak, although Senegal and Nigeria have since been declared virus-free by the WHO.
Malian authorities have now quarantined and are monitoring 43 people who have been in contact with the infected girl. They include 10 health workers.
The girl is being treated in the western town of Kayes. A statement from Mali's health ministry said her condition was improving considerably, thanks to good treatment.
She was brought to a local hospital on Wednesday and her blood sample was Ebola-positive.
At the scene: Alou Diawara, BBC Afrique, Bamako
People are afraid in Mali's capital, Bamako, but life is carrying on as normal. A few people have stopped shaking hands but physically greeting people is an important part of life in Mali and for most this has not changed.
Some hotels have placed bottles of anti-bacterial gels at their entrances but for ordinary Malians, gel remains too expensive. The government has been running public information broadcasts telling people to wash their hands with soap. But though soap is not expensive, most still wash their hands with water alone.
Many Malians have friends and family in Guinea and several buses and taxis travel between the two countries each day.
With the support of the WHO, Mali's health system has been preparing for an outbreak of Ebola for several months. But there is a culture here of visiting people when they are sick to wish them a speedy recovery.
This will have to change if Ebola becomes more widespread.
The WHO has three experts in Mali evaluating its ability to cope with Ebola and will send at least four more over the next few days, spokeswoman Fadela Chaib said.
The girl's mother died in Guinea a few weeks ago and the child was then brought by relatives to Mali.
With porous borders, countries neighbouring Guinea, Sierra Leone and Liberia are on high alert for possible imported cases of the virus, says BBC Africa health correspondent Anne Soy.
Anne Soy reports on the case from the UN crisis hub in Ghana
The current outbreak is the deadliest since Ebola was discovered in 1976
Separately, a New York doctor who recently returned from Guinea has tested positive for the disease.
In New York, Dr Craig Spencer, who treated Ebola patients while working for the charity Medecins Sans Frontieres (MSF), came down with a fever on Thursday, days after his return, officials say.
How Ebola survivors’ blood is saving lives
- Symptoms include high fever, bleeding and central nervous system damage
- Spread by body fluids, such as blood and saliva
- Fatality rate can reach 90% - but current outbreak has mortality rate of about 70%
- No proven vaccine or cure
- Fruit bats, a delicacy for some West Africans, are considered to be virus's natural host
Craig Spencer returned to New York from Guinea on 17 October
He is the first Ebola case diagnosed in New York, and the fourth in the US.
Dr Spencer, 33, left Guinea on 14 October, and returned to New York City on 17 October via Europe. On Tuesday he began to feel tired and developed a fever and diarrhoea on Thursday.
He immediately contacted medical services and was taken to the city's Bellevue Hospital.
Mayor Bill de Blasio said there was "no reason for New Yorkers to be alarmed".
Ebola patients are only infectious if they have symptoms, and the disease is only transmittable through bodily fluids, experts say.
