Scientists have determined that a strain of bird flu virus can infect humans, the Agriculture Ministry of Russia said.
The virus caused the deaths of hundreds of birds in a section of Siberia this month, but no human infections have been reported.
In a brief statement, the ministry identified the virus as avian flu type A H5N1.
"That raises the need for undertaking quarantine measures of the widest scope," the statement said. Ministry officials could not immediately be reached for elaboration.
Strains of bird flu have been hitting flocks throughout Asia and some human cases have been reported there. Since 2003, bird flu has killed at least 57 people in Vietnam, Thailand, Cambodia and Indonesia, which reported its first three human deaths this month.
The outbreak in Russia's Novosibirsk region apparently started about two weeks ago when large numbers of chicken, geese, ducks and turkeys began dying. Officials say that all dead or infected birds were incinerated. But it is unclear whether that would effectively stop the virus from spreading.
Earlier this week, Russia's chief government epidemiologist, Gennady Onishchenko, said the appearance of the virus in Russia could be due to migrating birds that rest on the Siberian region's lakes.
A recent report released by the journal Science said the finding of the H5N1 infection in migrant birds at Qinghai Lake in western China "indicates that this virus has the potential to be a global threat."
The reports echo concerns voiced by the World Health Organization, which urged China to step up its testing of wild geese and gulls. A WHO official estimated that the flu had killed more than 5,000 wild birds in western China.
The outbreak was first detected about two months ago in bar-headed geese at China's remote saltwater lake, which is a key breeding location for migratory birds that overwinter in southeast Asia, Tibet and India. The virus has hit that species the hardest, but also affects brown-headed gulls and great black-headed gulls, the AP reports.
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