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MOSCOW — Thirteen members of a nomadic Siberian community have been hospitalized after a heat wave thawed the carcass of an anthrax-infected reindeer and sparked an outbreak of the disease.

Around 1,500 of the animals have died from the highly infectious disease since Sunday, the government of Russia's Yamalo-Nenets autonomous district announced on its website Tuesday.

Reindeer gather in Russia's Yamalo-Nenets autonomous district on August 2, 2015. Sergei Karpukhin / REUTERS FILE

A state of emergency has been imposed throughout the region in western Siberia due to the incident — the first of its kind since 1941.

The carcass of a reindeer thought to have died from anthrax decades ago thawed and released the bacteria, sending the disease rippling through a population of animals already weakened by unusually high temperatures, according to local officials.

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Temperatures in the Yamal tundra above the Arctic Circle have hit highs of 95 degrees this summer, compared to an average of 77 degrees.

A map showing the location of Russia's Yamalo-Nenets autonomous district. Google Maps

At least 63 members of the Nenet community have been relocated as a result of the outbreak, their tents disinfected and children sent to a boarding school, the government said. The Nenets are traditional deer-herders and their livelihoods are linked to the animals.

A mass vaccination of reindeer is underway in the region, local officials said.

It may be too late for many of the animals because anthrax can kill deer within three days of infecting them, Vladimir Bogdanov, a biology professor with the Russian Academy of Sciences, told the RBC news website.

Yamal authorities stopped vaccinating reindeer 10 years ago because there had been no outbreaks for more than half-a-century — an apparent mistake, Bogdanov added.

A microscopic picture of spores and vegetative cells of Bacillus anthracis — which causes the disease anthrax — is pictured in this file photograph. Reuters / Reuters, file

Local authorities said they were considering the best way to dispose of dead reindeer. The usual method — burning — has severe risks in the tundra, as much of Siberia is already engulfed in wildfires.

Anthrax has a mortality rate of 25 to 80 percent, depending on a strain.

It was explored as a biological weapon by the Soviet Union during the Cold War, though never used.

Anthrax bacteria can remain dormant in dead bodies for decades, spreading to living organisms when exposed to them.