Egypt quarantines university dorm over H1N1 cases

* Two U.S. students in Egypt test positive for H1N1 virus

* Dormitory at American University in Cairo quarantined

(Adds university suspends classes, paragraph four)

CAIRO, June 8 (Reuters) - Egypt has detected the H1N1 flu virus in two students at the American University in Cairo and has put 140 more under quarantine in their Nile island dormitory, health and university officials said on Monday.

Police wearing face masks stood guard at barriers outside the multi-storey dormitory in the upmarket neighbourhood of Zamalek that houses mainly foreign students from Western and other Arab countries. No one was allowed in or out.

"There are two students who have confirmed positive H1N1 test results," university spokeswoman Rehab Saad El-Domiati said, adding that both infected students were American. "As a result, the dormitory has been quarantined for 24 hours."

A third student was hospitalised as a precaution with a fever. The university, a popular destination for U.S. exchange students, suspended classes for the week, and all students living in the dormitory were being tested for the virus.

Egypt, already hard hit by the much more deadly H5N1 bird flu virus, detected its first H1N1 case last week in a 12-year-old American girl who arrived for a holiday in the most populous Arab country. The case was the first in Africa.

The airborne H1N1 virus has now been diagnosed in more than 21,000 people worldwide, and has killed at least 125, mostly in Mexico, according to the World Health Organisation.

Egypt, whose poultry industry was decimated by the arrival of bird flu in early 2006, fears another flu virus could spread quickly in a country where most of the roughly 76 million people live in the densely packed Nile Valley, many in crowded slums.

Egypt had stepped up surveillance measures at the airport to try to prevent the arrival of the disease, including by installing thermal monitors that helped detect and swiftly isolate the country's first H1N1 case.

But the American University students who tested positive for the virus were believed to have arrived in late May on two separate flights from the United States, casting doubt on whether Egypt's airport measures could detect all cases.

Egypt has reported 29 human cases of bird flu this year including a toddler who tested positive on Sunday -- nearly four times the number reported in 2008. (Additional reporting by Ashraf Fahim in Cairo; Writing by Cynthia Johnston; Editing by Jon Hemming)