* Flu virus prompts countries to limit pork, meat imports
* Russia, China, Indonesia, Thailand, others impose bans
* Affects Mexico, U.S., New Zealand, Canada, Central America
* EU, South Korea, Japan, Kosovo tighten checks, avoid bans
(Adds background on H1N1 flu paragraphs 3, 4, 10) By Laura MacInnis
GENEVA, May 4 (Reuters) - Up to 20 countries worldwide have banned imports of pork and other meat in response to an outbreak of a new flu virus, according to documents from the World Health Organisation.
Although the H1N1 strain is not food-borne, fears that it may spread through animal products have prompted restrictions on live pigs, pork, cattle, poultry, livestock, feed and animal semen from countries with reported infections, according to the list obtained by Reuters on Monday.
More than 1,000 people have been infected with the virus that is thought to spread through sneezes, coughs and droplets like the common flu. WHO labs have confirmed 26 deaths from H1N1, all but one in Mexico, the epicentre for the outbreak.
Canadian authorities on Saturday also reported the presence of the virus in a swine herd, which was apparently infected by a farm worker who had been to Mexico. That caused the WHO to called for extra caution in handling live animals.
The WHO's pork import restriction list was compiled from official statements and media reports. Countries identified as having imposed bans include Russia, China, Croatia, Indonesia, Thailand and Ecuador.
Global trade in pork meat is worth about $26 billion a year.
The three countries most affected by the bans -- Mexico, the United States and Canada -- are among the world's top pork exporters along with the European Union, Brazil, Chile, China and Hong Kong.
Other countries whose exports would be blocked by the bans include New Zealand, Spain, France, Israel, Costa Rica, El Salvador, Colombia, Cuba, Nicaragua, Panama, Honduras, Guatemala and the Dominican Republic.
The H1N1 virus is genetically a mixture of two swine flu strains, with bits of human and bird genetic material.
News about its emergence and spread caused a drop in the market price of hogs and caused Russia, China, Ecuador and other countries to promptly block imports of pigs and pork, despite reassurances from the WTO that they posed no sanitary risks.
The new WHO list shows the number of restrictions has risen as the virus has continued to spread.
'NO JUSTIFICATION'
The Canadian swine herd infection was announced just days after the WHO said it would change the virus name to "A-H1N1" to clarify it was passing directly person to person instead of from a pig to a person.
Before that animal infection made headlines, the WTO and three United Nations agencies including the WHO said there was no justification for the imposition of trade restrictions on account of the H1N1 flu.
On Sunday, a food safety expert said that while pork meat posed no risks, extra precautions should be taken when handling live pigs to avoid spreading and catching the virus that the WHO says is on the brink of causing a pandemic.
"Trading meat, whether processed or raw or frozen meat, should not be restricted because there is virtually no risk of transmission that way," the WHO's Peter Ben Embarek said.
"You might have a risk with the live animals or when slaughtering it, but on the other side, as soon as you are dealing with the final product there is no big risk."
Under international trade rules, countries are allowed to stop imports of goods that are seen to pose health risks or fall short of sanitary standards.
Canada's trade minister Stockwell Day said governments should "make decisions that are scientifically based".
"This is not an influenza which is carried in the product itself, it's an airborne transmission," he said in Lithuania.
"We would expect those countries, which have gone ahead with the ban or were thinking about it, would stop and have a look at scientific guidelines and would recognise that the meat itself is not a problem."
The European Union, South Korea, Japan and Kosovo have all said they would avoid any pork import bans for the time being, but several are increasing their monitoring of live pigs and pork products, according to the WHO list.
Though Switzerland is on the roster as blocking imports, a spokesman for the Swiss Federal Veterinary Office said there are no pork or meat bans in place in response to the H1N1 virus.
Others listed by the WHO as having imposed pork and meat restrictions are Thailand, Jordan, the Philippines, Ukraine, Lebanon, Azerbaijan, Bahrain, Kazakhstan, Macedonia, Montenegro, Suriname, the United Arab Emirates and Belarus.
Egypt has ordered the slaughter of all its 300,000 to 400,000 pigs as a precaution against H1N1, a move the United Nations said was "a real mistake". (Additional reporting by Nerijus Adomaitis in Vilnius; Editing by Jon Hemming) (For more Reuters swine flu coverage, please click here: http://www.reuters.com/news/globalcoverage/swineflu )