A 50-year-old woman infected with Ebola has died in western Uganda, a day after her five-year-old grandson died.
They are the first two cases reported in the country since the virus spread from neighbouring Democratic Republic of Congo, where nearly 1,400 people have died.
Three suspected Ebola patients have also run away from an isolation centre.
The head of a major medical charity has called the latest outbreak of Ebola in central Africa “truly frightening”.
Dr Jeremy Farrar, the director of the Wellcome Trust, said the epidemic was the worst since that of 2013-16 and has showed “no sign of stopping”.
He said the spread was “tragic but unfortunately not surprising”. He warned that more cases were expected, and a “full” national and international response would be needed to protect lives.
On Friday the World Health Organization (WHO) will decide whether the outbreak should now be deemed a public health emergency.
The grandmother and grandson are said to have travelled across the border to DR Congo on Sunday, where they are suspected to have contracted the virus from an elderly male relative who later died.
The three-year-old brother of the boy who died on Monday – who is confirmed as having Ebola – and four other members of his household have been repatriated to DR Congo, Uganda’s health ministry said on Thursday.
Uganda now has three people being held in isolation because health officials fear they could be infected – their status is being confirmed with blood tests.
How prepared is Uganda?
Analysis by Patricia Oyella, BBC Africa, Kampala
This isn’t the first time the virus has struck the country. Outbreaks in 2012, 2007 and 2000 have prompted the health ministry to build capacity, says Director of Clinical Services Dr Charles Olaro.
Public health information campaigns broadcast to at-risk areas have been key in preventing the spread since the first case of Ebola was reported over the border in DR Congo last August. Mass gatherings, including market days and prayers, have been cancelled. Market days in the town of Kasese attract an estimated 20,000 people at the border area.
Uganda’s health ministry and the WHO said a rapid response team had been dispatched to identify others at risk. The country has already vaccinated about 4,700 health workers against the disease, according to a joint statement by WHO and Ugandan health officials. Ebola screening centres are in operation along the border with DR Congo as well as other major entry and exit points.
Authorities have identified 22 high-risk districts – places that are close to the border and have high levels of movement – and deployed medical monitors to spot and manage any cases they find.
A database of experts is on hand to deal with different scenarios, the health ministry says, and Uganda also benefits from the expertise of health workers it deployed to contain previous outbreaks in West Africa.
What’s the situation in DR Congo?
Nearly 1,400 people have died over the last 10 months – around 70% of all those infected.
The outbreak is the second-largest in the history of the disease, with a significant spike in new cases in recent weeks.
Only once before has an outbreak continued to grow more than eight months after it began – that was the epidemic in West Africa between 2013-16, which killed 11,310 people.
Some have predicted it could take up to two more years to bring to an end. The WHO has twice ruled that this Ebola outbreak is not a yet global emergency. I
Efforts to contain the spread have been hindered by militia group violence and by suspicion towards foreign medical assistance.
Nearly 200 health facilities have been attacked in DR Congo this year, forcing health workers to suspend or delay vaccinations and treatments. In February, medical charity Médecins Sans Frontières (MSF) put its activities on hold in Butembo and Katwa – two eastern cities in the outbreak’s epicentre.