AFP/ Freetown

More than 20 children have been quarantined at a British-run orphanage in Sierra Leone after one of its staff was diagnosed with Ebola.

St George Foundation orphanage, on the outskirts of the capital Freetown, said Sierra Leonean employee Augustin Baker collapsed during a meeting last week.

"Augustin transferred to Kerry Town Ebola treatment centre and Ebola is confirmed. Four staff (were) exposed while assisting Augustin to hospital," said a statement dated Sunday on the charity's website.

The orphanage has placed itself under voluntary quarantine, with 10 staff and 25 children confined to the centre for 21 days.

The charity added that Baker, who is being treated at a British run and funded clinic, was "as well as can be expected at this stage".

The organisation, which has been in Sierra Leone for 11 years, says it has helped 175 Ebola orphans since the outbreak began in May last year.

One of the deadliest viruses known to man, Ebola is spread through direct contact with the bodily fluids of an infected person showing symptoms such as fever or vomiting or the recently deceased.

The United Nations children's fund said in January more than 16,000 children had lost at least one parent or main carer to the west African epidemic.

The outbreak has killed more than 9,500 people in Sierra Leone, Liberia and Guinea but the leaders of the three countries have vowed to achieve zero Ebola infections by mid-April.

Sierra Leone has seen a cumulative total of more than 11,000 cases during the epidemic which has raged in the region for more than a year.

The rate of infection has greatly reduced in recent months, and the focus of the response is the western area, including Freetown, where the crisis has yet to be brought under control.

The government launched a door-to-door search last week for Ebola patients and bodies it suspects are being hidden from the authorities.

Dozens of healthcare workers fanned out across remote parts of Port Loko district, east of Freetown, after a spike in cases attributed to unsafe burials.

The country placed 700 homes in the capital Freetown in quarantine earlier this month following the death of a fisherman who tested positive for Ebola.