(updates number infected, adds screening by Kenya)

By Tim Cocks

KAMPALA, Dec 6 (Reuters) - A new strain of the deadly Ebola virus is thought to have infected 94 people and killed at least 22 in Uganda, prompting neighbouring Kenya to begin screening at its shared border, officials said on Thursday.

Dr. Sam Zaramba, Uganda's director of health services, told Reuters a doctor had died in Kampala's Mulago Hospital after looking after a patient in its isolation ward. Three other medical staff died after treating infected patients.

Besides the doctor and patient in Mulago, all other cases and deaths had occurred where the outbreak started in Uganda's western Bundibugyo district, bordering the Democratic Republic of Congo, he said.

"We've had one more admission today, someone in Bundibugyo. It is 94, now," Zaramba said.

"Twenty two have died. Out of them, four (are) health workers, one a doctor. He died in Mulago," Zaramba said earlier.

Only 58 cases have so far been confirmed in laboratory tests, Uganda says. But more people falling ill and a rising death toll since the outbreak started in August has caused panic in the east African country.

Neighbouring Kenya has been screening travellers entering from Uganda at the Busia crossing -- on the main road out of Kenya's west into east and central Africa -- since last week, health officials said.

"Screening is going on at Busia. People are being asked questions about where they have travelled and their health," Kenya's head of medical services, Dr. James Nyikal, told Reuters.

The Ugandan government confirmed the fever was Ebola a week ago.

"All medical staff dealing with Ebola have been issued with protective gear," Zaramba said.

Genetic analysis of samples taken from some victims shows this virus is a previously unrecorded type of Ebola, making it a fifth strain, U.S. and Ugandan health officials say.

The World Health Organisation is concerned about the way the virus keeps mutating.

But Ugandan officials say the unusually low death rate of this type -- at roughly 22 percent when the virus normally kills between half and 90 percent of those infected -- shows it is less lethal than previous epidemics.

Uganda was last hit by Ebola outbreak in 2000, when 425 people caught it and just over half died.

This year, an epidemic broke out in Congo -- where some of the first recorded cases in 1976 gave the virus its name after the country's Ebola river. It killed 187 people and infected up to 264. (for background on Ebola click on [ID:nL06277921] (Additional reporting and editing by Bryson Hull)

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