Poultry farm workers became infected with avian flu in the first known case of people contracting the strain.
Seven workers at a poultry factory in southern Russia were infected with the H5N8 strain in an outbreak in December, Anna Popova, head of consumer health watchdog Rospotrebnadzor, said on Saturday.
It is the first case where an avian flu virus strain called A (H5N8) is transmitted from birds to humans.
Russia has reported the matter to the World Health Organization (WHO).
Outbreaks of the H5N8 strain have been reported in Russia, Europe, China, the Middle East and North Africa in recent months, but so far only in poultry.
Other strains – H5N1, H7N9, and H9N2 – are known to spread to humans.
Russia reported a human infection to WHO “a few days ago when we were absolutely certain of our results,” Popova said on state television Rossiya 24.
There is still no evidence of inter-human transmission, she added.
“This situation has not evolved,” she said.
In an email, the WHO European arm announced that Russia had been informed of a case of human infection with H5N8 and confirmed that it would if it was confirmed that the strain had infected humans for the first time would have.
“Preliminary information suggests that the reported cases were workers who were exposed to flocking birds,” the email said.
“They were asymptomatic and no person-to-person transmission has been reported.
“We are in discussion with national authorities to gather more information and assess the public health impact of this event,” the email added.
The majority of human avian influenza infections have been linked to direct contact with infected live or dead poultry, although properly cooked feed is considered safe.
Avian flu outbreaks often cause poultry plants to kill their birds to prevent the virus from spreading and to avoid importing countries from imposing trade restrictions.
The vast majority of cases are transmitted through migration of wild birds. As a result, the producing countries tend to keep their poultry indoors or protect them from contact with wild animals.
The Siberian Vector Institute announced on Saturday that it would start developing human tests and a vaccine against H5N8, the RIA reported.
In 2007, another strain of avian flu, H5N1, spread across Asia, killing six out of ten people who got it.
However, the disease went away for reasons that are not entirely clear to scientists.
A total of 455 people died from the H5N1 strain.
Not a single H5N1 infection has been identified in humans since February 2017.