A five-year-old boy in Uganda has become the first cross-border victim of the current Ebola outbreak.
The current outbreak of the disease in the Democratic Republic of Congo is the second largest in history and shows no sign of slowing down or subsiding since the first cases were announced in August.
The virus has infected more than 2,000 and killed 1,367 people as of June 5 2019, according to the World Health Organization.
The boy, part of a Congolese family who crossed into Uganda earlier in the week, was vomiting blood and died overnight, said officials.
A special committee has been placed on standby by the World Health Organization to advise on whether a global health emergency should be declared now that the Ebola outbreak in the DRC has spread beyond the country's borders.
The boy's three-year-old brother and 50-year-old grandmother have also tested positive for the highly contagious disease and are being treated at an isolated hospital near the border.
The dead boy's uncle is now among seven suspected Ebola cases in Uganda, along with the three which have been confirmed.
Authorities are now trying to find out how the family, exposed to the virus via a sick relative in the DRC, managed to cross a border where health officials have been screening millions of travellers for months.
Experts have long feared Ebola could spread to neighbouring countries because rebel attacks and community resistance are hampering the work being done to halt the spread of the virus, which so far has been contained to eastern DRC - one of the world's most turbulent regions.
The virus can spread quickly via close contact with bodily fluids of those infected and can be fatal in up to 90% of cases.
The DRC's health ministry said a dozen members of the boy's family had showed symptoms of Ebola.
They were not placed in isolation and instead were told to remain where they were staying until transport was found to an Ebola treatment unit in Beni, DRC, Dr Dominique Kabongo, coordinator of Ebola response teams in nearby Kasindi, has said.
However those instructions appear to have been ignored and half of the family crossed into Uganda, while five of those who remained have tested positive for Ebola since being taken to Beni, the health ministry said.
"Many people are evading (border) customs and using small footpaths and it is difficult for us to follow the contacts," Dr Kabongo said.
Authorities on both sides of the border have said they are doing their best to close unauthorised crossings.
Ugandan health teams "are not panicking," Henry Mwebesa, the national director of health services, has said.
He cited the east African nation's experience battling previous outbreaks of Ebola and other haemorrhagic fevers.
"We have all the contingencies to contain this case," Mr Mwebesa said.
"It is not going to go beyond" the boy's family, he said.
The child's mother, who is married to a Ugandan, knew where to cross the border unofficially, he added.
In the border area where the family is thought to have crossed, surveillance teams patrolled the Ugandan side on Wednesday.
Some footpaths, however, remained unguarded.
Some people have waded across the shallow Lubiriha River instead of using a bridge to avoid being stopped by officials.
People from the DRC "have failed to understand that Ebola is there, they think that it is witchcraft which is killing them," a Ugandan Red Cross official, Francis Tumwine said.
A Congolese trader, Muhindo Kaongezekela, added: "We are not sure if there's Ebola in Congo.
"In Congo, if they find you with a headache, they take you to the hospital and later say they died of Ebola."
Uganda is more stable than eastern Congo, and for the first time an experimental but effective Ebola vaccine is being widely used, with more than 130,000 doses distributed.
The country has been preparing for cases in the country from neighbouring DRC for eight months, with an app developed to allow people to monitor their temperatures - one of the signs of the virus.
Uganda has vaccinated nearly 4,700 health workers, and WHO is shipping another 3,500 doses this week for health workers and contacts of those infected.
While preparations are in place, Ebola is still feared in the African nation where multiple outbreaks have occurred over the years.
An outbreak in the north in 2000 infected 425 people and killed more than half of them.
The WHO expert committee has twice decided that the current outbreak, while of "deep concern", is not yet a global health emergency and has advised against travel restrictions.
However, international spread is one of the major criteria for the virus to be declared a global health emergency.
The first cross-border case is "tragic but unfortunately not surprising," said Dr Jeremy Farrar with the Wellcome Trust, which funds Ebola vaccine research.
While Uganda is well-prepared, he added: "We can expect and should plan for more cases in [the DRC] and neighbouring countries.
"This epidemic is in a truly frightening phase and shows no sign of stopping anytime soon."