A 30-year-old woman was first treated on 17 December, before a brother and sister, aged 26 and 15, fell ill.

The World Health Organization confirmed the test results on the three, who live with 30 other family members raising poultry in a town north of Cairo.

The positive tests raise to 18 the total number of human cases in Egypt. Seven of those people have died.

The family live together in one house in the town of Zifta in Gharbiya province, about 80km (50 miles) north of Cairo.

Family farm

A WHO official said the family raised ducks, and the brother and sister had become infected after slaughtering the flock in an effort to stem the spread of the H5N1 virus.

The 30-year-old woman, who also developed symptoms, is recovering well in a Cairo hospital, said Hassan el-Bushra, a WHO regional adviser.

Three of the family's ducks had died of the virus, he added.

Egypt is a major route for migratory birds and is one of the countries worst hit by the virus outside Asia.

Government officials had hoped an initial outbreak of H5N1 among poultry in February had been contained and would not further affect the country's food supply.

In the Middle East, the disease is also known to be present in Iran, Iraq, Israel, Gaza and the West Bank.