(Bloomberg) -- Russia said it found the world’s first cases of the H5N8 strain of avian influenza in humans though the virus isn’t yet spreading between people.

Authorities have sent information on the seven cases detected in workers at a poultry farm in southern Russia to the World Health Organization, Anna Popova, the country’s public-health chief, said in televised comments on Saturday.

“It is not transmitted from person to person. But only time will tell how soon future mutations will allow it to overcome this barrier,” she said. The discovery of this strain now “gives us all, the whole world, time to prepare for possible mutations and the possibility to react in a timely way and develop test systems and vaccines.”

The affected workers at the poultry farm, where an outbreak among birds was reported in December, had mild cases and have recovered, Popova said.

The swift identification of the strain means work can start on development of testing to detect new infections and on potential vaccines, Rinat Maksyutov, head of the Vektor research center, which made the finding, told state television.

In November, Vektor reported that a new H5N8 flu strain was circulating in 15 Russia regions among poultry and wild birds, but was not considered dangerous to humans, the Interfax news service reported.

In 2012, health officials investigated a strain of bird flu that killed hundreds of wild ducks in southern Russia’s Krasnodar region for potential risks to humans.

More than 2 million ducks and other poultry were slaughtered in France as of the end of January due to outbreaks of avian flu or as a preventative measure, the country’s agriculture ministry reported.

There have been 862 laboratory-confirmed cases of human infection with the H5N1 strain of avian flu including 455 deaths since 2003 in 17 countries, the WHO said in a Dec. 9 report. Six of 14 cases of H5N6 avian flu in humans reported since 2014 were fatal, the WHO said in a post dated Nov. 2016.

“Though human infections with A(H5) viruses are rare and generally occur in individuals exposed to sick or dead infected birds (or their environments), they can lead to severe illness or death in humans,” the WHO said on its website.

(Updates with Vektor chief in fifth paragraph, WHO data in ninth)

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