CONAKRY (AFP) - A medical charity confirmed on Friday (March 18) its specialist Ebola clinic has reopened in rural southern Guinea to treat an infected woman and her child after the virus killed at least two of their relatives.

The Alliance For International Medical Action (ALIMA) said the pair were receiving treatment following positive tests for Ebola on Thursday, adding the patients came from a village 100km from Guinea's second city of Nzerekore.

"We hope that this new episode will be rapidly contained because today the authorities and communities are well versed in the appropriate measures to fight the disease," said Richard Kojan, a Conakry-based doctor for ALIMA.

The World Health Organisation (WHO) said on Friday Guinean health officials had alerted it to Ebola symptoms in the family's village on March 16, where three people had died in unexplained circumstances in the last few weeks.

The child being treated was a boy aged five, the WHO said.

An expert team was dispatched to conduct tests after the two new diagnoses, and a larger WHO deployment was en route.

"More specialists are expected to arrive in the coming days. Response teams will work to investigate the origin of the new infections and to identify, isolate, vaccinate and monitor all contacts of the new cases and those who died," the world health body said in a statement.

A source close to the local anti-Ebola coordination team told AFP that the two deceased relatives were a married couple who had both shown symptoms of vomiting and diarrhoea.

The four confirmed cases are the first in Guinea since the country was declared Ebola free at the end of last year, though a significant number of deaths are believed to have gone unreported.

The WHO refers to these isolated cases as "flare-ups" but maintains the original "chains of transmission" have been stopped in Guinea, Liberia and Sierra Leone.

The Guinea diagnoses came the same day the WHO declared a similar flare-up over in Sierra Leone, announcing there had been no new cases for 42 days - the length of two Ebola incubation cycles.

On Thursday the world health body was already warning that a recurrence of the deadly tropical disease - which has claimed 11,300 lives since December 2013 - remained a possibility.

"WHO continues to stress that Sierra Leone, as well as Liberia and Guinea, are still at risk of Ebola flare-ups, largely due to virus persistence in some survivors, and must remain on high alert and ready to respond," it said in a statement.