ZURICH (Reuters) - Switzerland reported the first case ofH5N1 bird flu in the country in two years in a duck onSempachersee lake, veterinary authorities said on Thursday.

The duck, the 33rd case of bird flu in Switzerland, showedno signs of illness, the Federal Veterinary Office said in astatement.

The other 32 discovered cases of bird flu were all reportedin early 2006, on Lake Geneva and Lake Constance.

Experts fear the H5N1 strain could mutate into a formeasily transmitted from person to person, leading to a pandemicthat could kill millions worldwide.

(Reporting by Sam Cage; Editing by Elizabeth Piper)