The authorities in the Democratic Republic of Congo have appealed for calm after the first case of Ebola was diagnosed in the main eastern city of Goma.
The city is the biggest where a case of the killer disease has been confirmed since an outbreak started in eastern DR Congo last August, but the government said chances of it spreading were "low".
The patient is a pastor who had been preaching at a church in another town, Butembo, where he would have touched worshippers "including the sick", the country's health ministry said Sunday.
His symptoms first appeared last Tuesday.
The preacher left for Goma from Butembo, one of the towns most affected by the outbreak, by bus on Friday, and arrived two days later where "the results of the laboratory test confirmed that he was positive for Ebola", the ministry said.
"Given that the patient was quickly identified, as well as all the passengers on the bus from Butembo, the risk of the disease spreading in the city of Goma is low," it added.
The other passengers, 18 in all, and the driver will be vaccinated against Ebola on Monday, said the ministry, and urged the population of one of Africa's largest countries to "keep calm".
At the weekend, however, two Ebola awareness campaigners were murdered in their homes in the North Kivu province, where locals view foreign health care providers with deep suspicion.
The pair were killed after months of threats, the health ministry said.
The UN is convening a "high-level event" in Geneva Monday to discuss response and preparedness for the Ebola outbreak.
It will be attended by government ministers from the DR Congo and Britain, senior officials of the World Bank, the World Health Organization, and other UN agencies.
Health workers in Goma, which has a population of about one million and is the capital of North Kivu province, were vaccinated as early as December when the outbreak first hit Butembo some 300 kilometres (180 miles) north.
The two towns are separated by poor roads under the threat of armed groups.
The latest Ebola outbreak in eastern DR Congo has killed 1,655 people, according to a health ministry bulletin on Saturday.
Nearly 700 were cured, and total of 160,239 people have been vaccinated against the highly contagious haemorrhagic fever, it added.
The UN's World Health Organization had been hopeful it would be able to contain the latest epidemic, thanks in part to a new vaccine.
In June, the WHO said the outbreak did not qualify as an international threat, even after an infected family travelled to neighbouring Uganda.
Efforts to tackle the crisis have been hampered by militia attacks on treatment centres, in which some staff have been killed, and hostility to medical teams from outside -- fuelled by local politicians actively trying to turn people against them.
Insecurity in the restive region, including a long-standing presence of various rebel groups in the provinces of Ituri and North Kivu, has made it difficult for health workers to access people who may have been exposed to the virus.
The disease spreads when humans touch the blood, body fluids, secretions or organs of an infected person, or objects contaminated by such fluids.
The outbreak is the 10th in DR Congo in 40 years, putting all countries in the region on alert.
It is the second deadliest on record globally, after the epidemic that struck West Africa in 2014-2016, killing more than 11,300 people.