Officials said seven workers at a poultry plant in the south of the country had been infected following an outbreak there in December.
"All seven people... are now feeling well," said the head of Russia's consumer health watchdog, Anna Popova.
She said that adequate measures had been quickly taken to stop the spread of infection.
There was no sign of transmission between humans, Ms Popova said, adding that the case had been reported to the World Health Organization.
She praised "the important scientific discovery" by Russia's Vektor laboratory, which had isolated the strain's genetic material from the infected workers.
"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.
She said Russian scientists could now start working on developing test systems.
Other strains of bird flu occasionally infect humans and have led to deaths - but this is the first report of the H5N8 strain being passed on.