The area is home to an estimated 250,000 people and considered the epicentre of the disease.
Many villagers are reportedly unwilling to co-operate with medical authorities.
Also known as Ebola Hemorrhagic Fever (EHF).
Named after a river in the Democratic Republic of Congo (DRC) where it was first recognised.
Ebola is characterised by the sudden onset of fever, intense weakness, muscle pain, headache and sore throat.
This is often followed by vomiting, diarrhoea, rash, impaired kidney and liver function and, in some cases, both internal and external bleeding.
The fever has an incubation period of two to 21 days.
No specific treatment or vaccine is available.
The Ebola virus is transmitted by direct contact with the blood, secretions, organs or other bodily fluids of infected people.
Burial ceremonies where mourners have direct contact with the body of the deceased person can play a significant role in the transmission of Ebola.
Health care workers have frequently been infected while treating Ebola patients.
Sam Zaramba, Uganda's director of health services, told Reuters news agency that a doctor had died in the Mulago hospital in Kampala, the capital, after looking after a patient in its isolation ward.
Three other medical staff died after treating infected patients.
According to Zaramba, all other cases and deaths had occurred where the outbreak started.
Zaramba said: "We've had one more admission today, someone in Bundibugyo. It is 94 now."
"Twenty-two have died. Out of them, four [are] health workers, one a doctor. He died in Mulago."
Kenya has been screening travellers entering from Uganda at the Busia crossing - on the main road out of Kenya's western region, into east and central Africa - since last week, health officials said.
James Nyikal, the head of medical services, said: "Screening is going on at Busia. People are being asked questions about where they have travelled and their health."
Ugandan health officials say that the genetic analysis of samples taken from victims shows the virus as a previously unrecorded type of Ebola, making it a fifth strain.
They also said that the low death rate of this type - at roughly 22 per cent, when the virus normally kills between half and 90 per cent of those infected - shows it is less lethal than previous epidemics.
Uganda was last hit by an Ebola outbreak in 2000, when 425 people were infected and over half died.
Some of the first recorded cases of Ebola were found in the DRC in 1976.
It killed 280 people and infected up to 380.