Eight people are confirmed as infected with anthrax, a rare but deadly bacterial disease. It is believed to have spread from reindeer.
More than 2,300 reindeer have died in the outbreak, in the Yamalo-Nenets region of Siberia. Reindeer-herding families have been moved out.
A heatwave has fuelled the disease.
Temperatures in the danger zone - now under quarantine - have soared to 35C.
Russia has sent troops trained for biological warfare to help deal with the emergency.
