The Swiss economics ministry has announced "targeted" preventive measures to protect poultry against avian flu carried by birds heading to Africa.
From October 15, poultry living within one kilometre of major lakes and rivers - where migratory birds infected with the H5N1 virus might stop to rest or drink - will be kept indoors.
"Within these regions ... free-range poultry will be banned as well as poultry markets and exhibitions," the ministry said on Friday.
Unlike the previous outdoor ban, which was imposed across the country from February 20 to May 1 this year, the latest lock-up only applies around lakes and rivers in low-lying parts of the country.
"The period of vigilance will not be limited to periods of migration, but throughout the winter," the ministry said, adding that the measures, to remain in place until April 30, 2007, could also be reinforced.
Thirty-two dead wild birds were found with the H5N1 virus last February and March in Switzerland, mainly around lakes. This led to a national order to bring poultry indoors that was lifted in May. No human cases were reported.
Monitoring of wild birds around lakes, as well as analysis of any dead birds found, continues, the ministry said.
Initial reaction to the new ban was generally understanding. The Swiss Farmers' Association (SFA) said targeted measures were the right thing to do and Kagfreiland, a farm animal protection organisation, deemed it a pragmatic solution.
Thomas Jäggi, spokesman for the SFA, said not imposing a nationwide ban was correct since measures against an epidemic had to take into account the risk factor.
He added that the length of the ban would enable those affected to prepare better than they were able to last year.
The preventive measures affect about 1,000 of the country's 17,000 professional farms and 4,000 of the 50,000 amateur chicken raisers – less than 10 per cent of the overall total, according to the economics ministry.
Switzerland's summertime water fowl population of 50,000 swells to 500,000 during the winter migration to African wintering grounds.
The lakes affected by the measures include the four largest: Lake Geneva, Lake Constance, Lake Neuchâtel and Lake Zurich.
Most European Union countries have relaxed measures requiring poultry to be kept indoors but authorities are ready to revive the order should risk levels increase. Switzerland is not a member of the EU.
In neighbouring Germany, the lock-up order remains in force, but large numbers of exemption permits have been issued during the period of low risk, allowing extensive free-range farming.
The Swiss measures are similar to those announced earlier this month by Belgium, according to Cathy Maret of the Federal Veterinary Office in Bern.
Neighbouring France, where a farm last February became the first case of the virus in domestic birds in the EU, is also expected to announce measures soon, she added.
swissinfo with agencies
From October 26 to December 16 last year, Switzerland banned the keeping of domestic poultry outdoors. The aim was to reduce the risk of Swiss animals coming into contact with infected wild birds during the autumn migration period.
A second outdoor ban was imposed from February 20 to May 1 this year after the H5N1 virus was found in wild birds in neighbouring countries during the spring migration.
The latest lock-up list – from October 15 to April 30 2007 – affects chickens, hens, turkeys, peacocks, guinea fowl, partridges, pheasants, quails, ducks, geese, ostriches, emus and rheas.
According to the latest WHO update, there have been 247 cases of human bird flu in ten countries since 2003, with 144 deaths.
The latest Swiss government plan says 1.85 million people could become infected with bird flu if the virus is able to pass from human to human.
In the event, 46,000 people would be admitted to hospital and around 7,400 people would die.