By Alaa Shahine

CAIRO (Reuters) - A 27-year-old Egyptian woman has tested positive for the deadly H5N1 bird flu virus, the 19th human case in the most populous Arab country, a World Health Organization official said on Wednesday.

The virus has killed 10 people in Egypt, which has the largest cluster of human bird flu cases outside Asia. Eight other positive cases have recovered since the virus first surfaced in Egyptian poultry in February.

"Unfortunately yes, there is a new case," said Hassan el-Bushra, regional adviser for communicable diseases surveillance for the World Health Organization.

He told Reuters that tests carried out by Egyptian health authorities were positive for the H5N1 virus and that he was awaiting the results of a second set of tests.

The official Middle East News Agency (MENA) identified the woman as Warda Eid Ahmed from the province of Beni Suef south of the capital Cairo. The agency quoted an Egyptian Health Ministry official as saying she has been hospitalized since January 13 with a serious pulmonary inflammation.

A health ministry spokesman said Ahmed had raised hens in her house. The ministry has dispatched a team to take samples from the rest of her family, he said.

Most people infected in Egypt had been in contact with poultry kept at home. The outbreak initially caused panic across the country and did extensive damage to the poultry industry.

But the Egyptian government said this month that poultry production had recovered to 1.8 million birds a day, still a little short of 2 million birds before the outbreak.

Three people from one family, including a 15-year-old girl, died of the virus in December, raising fears about the possibility of human-to-human transmission.

The fear that the virus could mutate into a form that passes easily from human to human was heightened in May when seven people in an extended family died of bird flu in Indonesia´s North Sumatra province.

The WHO has said limited human-to-human transmission is highly likely to have occurred in the Sumatra cases but said the transmission was not sustainable and occurred only during close, prolonged contact, such as a parent looking after an infected child.

Bird flu has killed 161 people worldwide since 2003, according to the latest WHO figures.

(Additional reporting by Cynthia Johnston)