The H5N8 strain of bird flu was first detected in humans, among seven infected workers at a Russian poultry center in December.
There is no evidence that the pressure is shifting between people, but Russia has reported that they have been distributed to the World Health Organization.
The staff are now feeling well, and “the situation has not improved further”, according to Dr Anna Popova, head of the consumer health watchdog Rospotrebnadzor. She said the workers were infected at the time of the outbreak at the plant.
Snoring has been reported in Russia, Europe, China, the Middle East and North Africa in recent months, but only in chickens.
Other strains of avian flu, including H5N1, H7N9 and H9N2, have previously been administered to humans.
The H5N8 snoring is lethal to birds, marking the first spread of the strain from animals to humans. Although Popova said that the strain did not seem to be able to spread among people, “only time will tell how soon future mutations will overcome this barrier”.
Recognizing this pressure “gives us all, the whole world, time to prepare for potential mutations and the opportunity to respond in a timely manner and to develop test systems and vaccines, ”She said.
The Vector Institute in Siberia on Saturday said it would begin developing human and vaccine tests against H5N8, according to RIA news agency.
Speaking on state TV, Popova said that Russia reported the developments to the WHO several days ago, “just as we have become completely convinced of our results”.
Most cases of avian influenza have been linked to direct contact with live or dead chickens, although properly cooked food is considered safe.
The cases tend to spread through migratory wild birds, forcing productive countries to keep their birds indoors or isolated from wildlife.
Influenza outbreaks often cause chicken plants to kill their birds to prevent the virus from spreading further, and often encourages other countries to impose trade restrictions involved. In the UK, five outbreaks of the H5N8 snort were detected in Gloucestershire, Dorset, Devon, Cheshire and Kent in November, prompting officers to enforce a zone ban in England, Scotland and Wales.
The Department for Environment, Food and Rural Affairs said all the birds in the affected areas had been “humanized” and control zones had been introduced.