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CAIRO, April 16 (Reuters) - A 2-year-old Egyptian boy has been infected with the deadly H5N1 bird flu virus, bringing the number of cases in the most populous Arab country to 50, state news agency MENA said on Wednesday.

MENA identified the child as Mahmoud Ibrahim Ramadan from the Nile Delta province of Sharkia, quoting Egypt's health ministry. It said he had been infected after exposure to household birds.

MENA said the boy started showing symptoms of the illness on Sunday and was taken to hospital the next day where he was treated with the anti-viral drug Tamiflu. He was in stable condition.

A total of 22 Egyptians have died of the H5N1 strain of bird flu since it first appeared in Egypt in February 2006.

About 5 million households in Egypt depend on poultry as a main source of food and income, and the government has said this makes it unlikely the disease can be eradicated despite a large-scale poultry vaccination programme.

Deaths from bird flu total more than 230 worldwide since 2003 and have been reported in several African and Asian countries. Egypt has been the worst-hit country outside of Asia. (Writing by Cynthia Johnston; Editing by Giles Elgood)