The H5N1 virus was detected in a wild duck on Lake Sempach, near Lucern, during a regular detection programme in which 200 specimens obtained from birds were tested.

The duck shows no symptoms of the disease, said the office, adding that the detected virus is almost identical with those detected in Europe last year.

Protective measures put in place since last October remain in place, and 'additional measures such as a ban on free-range poultry is not necessary at this time', said the office in a statement.

The risk of transmission to farmed poultry is small, indicated the office.

This case brings the total number of H5N1 cases detected in Switzerland to 33.

Previous cases were detected in February and March 2006 in wild birds found dead in the Lake Leman and Lake Constance regions.

Earlier this year, wild swans tested positive for the strain of bird flu in south-west England. -- AFP