Authorities in the Swiss town of Aarau have been told to stay home after an elected official travelled on a flight carrying someone infected with the H1N1 virus.
A 19-year-old man tested positive for the virus after the flight and is in isolation in hospital in Baden, near Zurich. Officials said he has a mild form of the flu and is recovering.
Swiss health authorities had warned anyone who travelled on the same US Airways flight 710 from Philadelphia to Zurich on April 25 to see their doctors.
One member of the Aarau town executive was among the passengers and as a result six other members and the town administrators have been quarantined at their homes until Tuesday.
Swiss health authorities confirmed on Saturday they were studying the condition of 23 people suspected of carrying the H1N1 virus that is behind the "swine flu" outbreak, but more people may be infected.
Of the 44 total cases brought to their attention so far, 20 have tested negative.
Authorities said they believed the virus could infect four times as many people as in a normal flu season.
swissinfo with agencies
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