Many people in Mali are at high risk of catching Ebola because the toddler who brought the disease to the country was bleeding from her nose as she traveled on a bus from Guinea, the World Health Organization warned Friday.

The U.N. agency is treating the situation as an emergency since many people may have had "high-risk exposures" to the 2-year-old girl during her journey through several towns in Mali, including two hours in the capital, Bamako. The girl was traveling with her grandmother.

The toddler died in an isolation tent at a hospital in the western city of Kayes on Friday, according to a nurse at the facility, who spoke on condition of anonymity because he was not authorized to speak to the press.

This is the first Ebola case in Mali and may expand to many more. The case highlights how quickly the virus can hop borders and even oceans, just as questions are being asked about what precautions health care workers who treat Ebola patients should take when they return home from the hot zone. Doctors Without Borders insisted Friday, after one of its doctors who worked in Guinea came down with Ebola in New York, that quarantines of returning health workers are not necessary when they do not show symptoms of the disease.
In the Mali case, however, the girl was visibly sick, WHO said, and an initial investigation has identified 43 people, including 10 health workers, she came into close contact with who are being monitored for symptoms and held in isolation. The child was confirmed to have Ebola on Thursday.

"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 agency said in a statement.

The girl first went to a clinic in Mali on Monday and she was initially treated for typhoid, which she tested positive for. When she did not improve, she was tested for Ebola, and she is now being treated in isolation in the western city of Kayes.

Mali has long been considered highly vulnerable to Ebola's spread since it shares a border with the Ebola-hit countries of Guinea and Senegal, and staff from WHO and the U.S. Centers for Disease Control and Prevention were already there helping to prepare for a case. More WHO staff are being deployed.

The Ebola outbreak began in Guinea and has since spread to five other West African countries. The virus has also been imported to Spain and the United States. On Thursday, Craig Spencer, who had been working with Doctors Without Borders in Guinea and returned home to the U.S. about a week before, reported a fever 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. But Doctors Without Borders said 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.