Exhibitors from some Asian countries have been barred from attending an international trade fair amid fears over Severe Acute Respiratory Syndrome (Sars).
The Swiss health authorities said they were concerned the highly contagious form of pneumonia could be spread by salespeople from the region.
Health officials said exhibitors from China, Hong Kong, Vietnam and Singapore would not be allowed to attend the World Watch and Jewellery Show, which opens on Thursday in Basel and Zurich.
Thomas Zeltner, director of the Federal Health Office, said close contact between exhibitors and visitors could lead to Sars being transmitted at the fairs.
He added that the decision had been taken after consultation with organisers and cantonal authorities.
The announcement has dealt a severe blow to the fairs' organisers, affecting some 350 - or one in six - of all exhibitors.
Around 6,000 visitors and exhibitors from southeast Asia were expected to attend the week-long event, which opens on Thursday.
According to the latest figures issued by the Geneva-based World Health Organization, at least 75 people around the world have died from Sars and around 2,000 others have been infected.
On Wednesday the WHO warned people against travelling to Hong Kong and China's southern Guangdong province because of fears over Sars, which is said to have originated in Hong Kong.
"Basel World" is one of world's largest luxury goods fairs. However, both sales and visitor numbers are likely to suffer this year as a result of the ongoing economic downturn and the war in Iraq.
Hong Kong's Trade Development Council admitted on Wednesday that the ban was a blow to local jewellery and watch manufacturers.
"TDC is seeking more information and legal advice on the full effect of the decree and how best to represent the interests of 317 exhibitors in the Hong Kong pavilion, which is second only to the Swiss pavilion in size," the local government-funded body said in a statement.
The TDC added that the vast majority of Hong Kong exhibitors had already arrived in Switzerland or were on their way.
Following an extraordinary session on Tuesday called to discuss Sars, the Swiss government said it did not envisage imposing restrictions on people returning from the Far East for the time being.
Switzerland has so far stopped short of issuing precautionary travel recommendations for Asia, but Zeltner said it might do so in the coming days, depending on how rapidly the disease spreads.
The toll of Sars cases in Switzerland rose on Wednesday to nine. The German-speaking part of the country announced its first suspected Sars victim, who is currently in isolation in a Zurich hospital.
On Monday, the Federal Health Office said eight people in French-speaking Switzerland had been treated for symptoms of the illness over the past few weeks, and that all but one patient had recovered.
swissinfo with agencies
At least 75 people worldwide have died from Sars, most of them in China.
Swiss authorities said they would issue a travel warning for Asia if the disease continued to spread.
The Federal Health Office has set up a hotline to deal with any enquiries regarding Sars.