The bird flu strain known as H5N8 has been detected in humans for the first time in Russia, in cases of animal-to-human transmission.
Seven employees at a poultry farm in the south of the country fell ill in December, Russia's chief public health officer Anna Popopa told state television on Saturday.
She said it was the first time this has happened in the world.
But she said those affected were doing well and had recovered. The disease's symptoms had been mild.
The Vektor research centre in the Siberian city of Novosibirsk said it had proven the transmission of the H5N8 virus and had already sent the scientific data to the World Health Organisation, Popova said.
The virus can be transmitted from animals to humans, she said, adding that she was not aware of any cases of human-to-human transmission.
In Germany, several outbreaks of bird flu have been detected in animals, with the highest illness and mortality rates observed in chickens and turkeys.
There are different subtypes of Avian influenza, and several have been known to infect humans.