Switzerland confirmed on Sunday its first case of avian flu in a duck found dead in the heart of Geneva, near the city´s famous jet d´eau fountain.

Swiss officials said it was not yet clear if the wild bird, found on Wednesday, was infected with the H5N1 strain of the virus which can infect humans.

"We have a first case of bird flu. It´s H5," Federal Veterinary Office spokeswoman Cathy Maret said.

A sample has been sent to a European reference laboratory in Britain to test for the H5N1 strain and results are expected by the end of the week, she said.

Switzerland has been on high alert for bird flu since the virus emerged in neighbours France, Germany, Austria and Italy.

The country this month ordered all poultry be kept indoors for an indefinite period to lessen the risk from the fast-spreading H5N1 virus that has killed millions of birds.

It remains difficult for humans to catch but the strain has killed more than 90 people worldwide since late 2003.

So far most human victims of the virus have had direct or indirect contact with infected birds but there are fears the virus will mutate into a strain easily passed among people, causing a pandemic in which millions could die. LITTLE HUMAN RISK

The Swiss Federal Veterinary Office said that in addition to the Geneva case, two wild ducks have tested positive for bird flu in the German towns of Ohningen and Singen, near Lake Constance in eastern Switzerland.

"Switzerland is equally concerned about these areas," the government agency said in a statement.

The Swiss cantons Schaffhausen and Thurgau, located near the affected German sites, on Sunday enacted controls to restrict the movement of poultry and other birds and boost testing.

Nearly 200,000 people live in Geneva, home to the U.N.´s European headquarters, the International Committee of the Red Cross and a smattering of private banks.

Local health authorities stressed there was little human risk from the single case in Geneva despite its urban site.

It was "extremely improbable" the virus would spread to humans living near the lake and "the risk from water is very, very close to zero," said Philippe Sudre, state medical officer for the Geneva canton.

In addition to the infected duck, Geneva sent samples from 16 other suspect birds for testing and all were found negative for avian flu, Laurence Mermod of the Geneva veterinary office said.

Among this group were three other dead birds found in the vicinity of the jet d´eau, and each tested negative for bird flu, Mermod said.

The jet d´eau is one of the most famous tourist attractions in Geneva. The pier to the jet d´eau, now barred to the public, is a popular destination for visitors who can stand under the fountain in summer and be doused by the water.