Russia said on Saturday that its scientists detected the first case of transmission of the H5N8 strain of avian flu to humans and alerted the World Health Organisation.
Anna Popova, who leads Russia's health watchdog Rospotrebnadzor, said scientists at a laboratory isolated the strain's genetic material from seven workers at a poultry farm in the south of the country, where an outbreak was recorded among the birds in December.
The workers did not suffer any serious health problems, she said.
"Information about the world's first case of transmission of the avian flu (H5N8) to humans has already been sent to the World Health Organisation," Ms Popova said.
There are different subtypes of avian influenza viruses.
While the highly contagious strain H5N8 is lethal for birds it had never previously been reported to have spread to humans.
Ms Popova said it was an "important scientific discovery" and that "time will tell" if the virus could further mutate.
"The discovery of these mutations when the virus has not still acquired an ability to transmit from human to human gives us all, the entire world, time to prepare for possible mutations and react in an adequate and timely fashion," Ms Popova said.
The State Research Centre of Virology and Biotechnology Vector in Koltsovo, outside the Siberian city of Novosibirsk, developed one of Russia's several coronavirus vaccines.
In the Soviet era the top-secret lab conducted biological weapons research and still stockpiles viruses such as Ebola and smallpox.
Vector chief Rinat Maksyutov said the lab was ready to begin developing test kits that would help detect potential cases of H5N8 in humans and to begin work on a vaccine.
The Soviet Union was a scientific powerhouse and Russia has sought to reclaim a leadership role in vaccine research under President Vladimir Putin.
Russia registered its Covid-19 vaccine Sputnik V in August, months before western competitors and even before large-scale clinical trials were conducted.
After initial scepticism in the West, The Lancet journal this month published results showing the Russian vaccine, named after the Soviet-era satellite, to be safe and effective.
Avian flu has raged in several European countries, including France, where hundreds of thousands of birds have been culled to stop the infection.
