The WHO, who raised its alert level for a pandemic from 4 to 5, said 17 people had died of the disease - 16 in Mexico and one in the U.S.
Mexico's health minister said on Saturday that 397 people had been diagnosed with the virus in the Central American country. U.S. health authorities said 141 people in the U.S. had been confirmed with the infection.
Although the illness has so far claimed few lives, the outbreak has sparked a number of dramatic media reports suggesting future death tolls "could" be in the tens of thousands or even millions.
The global health body also said well-cooked pork and pork products carry no risk of infection from the virus.
The head of Russia's Flu Research Institute said in an interview with RIA Novosti on Thursday that Russian scientists could create a vaccine to combat swine flu in three months.
