Transmission between humans has been confirmed in six countries.
WHO official Gregory Hartl said that although the current "round of activity" may be waning, "there is a high possibility that this virus will come back, especially in colder periods."
His colleague,food safety scientist Peter Ben Embarek recommended increased surveillance but denied the need to cull animals and confirmed that pork remained safe to eat. "From a consumer point of view there is no risk from consuming cooked pork products," he said.
Meanwhile, the threecountries worst affected by the outbreak, the US, Canada and Mexico, have urged their economic partners not to allow swine flu to disrupt international trade. Although WHO officials have confirmed that there is no evidence of the virus being transmitted through food, nearly 20 nations, including China and Russia, have banned imports of pigs and pork products from the three countries.
Confirming the impact of the import bans, analysts at financial consultants Moody's Economy.com said that the outbreak could stall global economic recovery. "The outbreak in Mexico and its rapid spread to other countries could interrupt trade and investment, exacerbating the worldwide recession for an uncertain period," said a spokesman.
In Egypt, pig farmers have battled with police in Cairo in a bid to prevent their animals being slaughtered. The government plans to cull all the nation’s pigs in a move that some have claimed to be racially motivated. Most of the nation’s pigs belong to the Coptic Christian minority.
The government said the cull was initially a precaution against swine flu but has now become a public health measure. No cases of swine flu have been reported in Egypt and the WHO says culls are unnecessary.
China has quarantined more than 70 Mexicans over swine flu fears prompting Mexican president Felipe Calderon to warn that some countries were "taking discriminatory measures because of ignorance."
Food Safety concern
Canada has confirmed the first case of the virus moving from humans to pigs after 200 animals on a farm in Alberta became infected by a worker who had recently returned from Mexico. Brian Evans, an official with Canada's food safety agency said both the man and the pigs were recovering. "There is no food safety concern related to this finding," he said.
In the US, 226 swine flu cases have been confirmed in 30 states. "Virtually all of the United States probably has this virus circulating now," said Dr Anne Schuchat of America's Centers for Disease Control and Prevention. Deaths are expected from the outbreak but every year about 36,000 US citizens die after contracting seasonal flu, she added.