However, speaking by video link from Geneva, she said there is "no indication that we are facing a situation similar to that in 1918," referring to the flu pandemic that killed tens of millions of people.
Nikolai Filatov, the head of Russia's consumer rights regulator Rospotrebnadzor's Moscow department, said Monday the virus could reach Moscow within two weeks.
"In line with preliminary expert calculations, the A/H1N1 influenza pandemic could reach Western Europe in May. In such a situation, the virus could reach Moscow within the next two weeks," he told a sanitary commission session in Moscow.
Earlier in the day, the WHO reported that the number of swine flu cases worldwide had reached 985 in some 20 countries.
"Should no measures be taken, up to 7 million people could become infected in Moscow. Three million could be seriously affected by the disease, 2.7 million will need outpatient treatment, 480,000 people will need hospitalization," Filatov also said.
The WHO raised on April 29 its alert level for a pandemic from 4 to 5.
The global health body has said well-cooked pork and pork products carry no risk of infection from the virus.
Russia and China, which jointly buy 20% of exported American pork, have so far blocked pork imports from California, Texas, New York, Alabama, Arizona, Arkansas, Georgia, Indiana, Kansas, Louisiana, New Jersey, New Mexico, Ohio, Oklahoma and Florida.
The Russian agricultural regulator Rosselkhoznadzor said the extended ban "applies to products produced after May 1."
Russia has also banned pork from Spain and three Canadian provinces - British Columbia, Nova Scotia and Ontario - which Rosselkhoznadzor listed as "risk zone 2."
The U.S. has urged Russia and China to lift their ban, citing the WHO's statements on the safety of pork.
