Dozens of people in the West African country of Mali are in isolation following the death of a two year old girl from Ebola.
The toddler was the country's first confirmed case of the virus and health officials fear many people could have been exposed.
The girl showed symptoms, including a bleeding nose, while travelling on a public bus through several towns, the World Health Organisation (WHO) said.
Forty-three people, including 10 health workers, who came into contact with her have been identified and isolated.
The girl was being treated in the western town of Kayes, after arriving at a hospital on Wednesday.
The child had travelled more than 1000 kilometres from Guinea through the capital, Bamako, to Kayes.
"The child's symptomatic state during the bus journey is especially concerning, as it presented multiple opportunities for exposures, including high-risk exposures, involving many people," the WHO said.
The girl's mother died in Guinea a few weeks ago and the child was then brought by relatives to Mali.
Mali has become the sixth West African country to be affected by the outbreak.
The outbreak has killed nearly 5000 people this year, mainly in Liberia, Sierra Leone and Guinea.
Senegal and Nigeria have successfully contained outbreaks.
Spain and the United States are treating a handful of cases.