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.”