A heatwave that hit Siberia this summer may have unleashed a horde of long-frozen bacteria that now threatens the entire region. An outbreak of anthrax in western Siberia has claimed the lives of 1,500 reindeer since July 24, and 40 Yamal nomads, including four children, have been hospitalized. Some reports say that a 12-year-old boy has died.

Within days, the anthrax decimated local reindeer populations, and tens of members of the indigenous Nenet community have been relocated. The local governor has declared a state of emergency, and some of the herders are facing quarantines that may last until September, according to NBC News.

Denoting this as a “zombie outbreak” may sound a bit strange, but this is arguably the best way of describing what’s happening right now in western Siberia. Back in 1941, an earlier outbreak of anthrax hit the area, and plenty of reindeer back then were felled by it. One of these unfortunate ruminants collapsed into the tundra for the very last time, and was partly preserved thanks to the frigid local conditions.

For 75 years, this frozen carcass remained untouched and undisturbed. However, this summer, an unusual heatwave hit the tundra, raising temperatures up to 5.6°C (10°F) above normal – perhaps a symptom of man-made climate change. This was enough to thaw out the dead reindeer, and the long-dormant bacteria within it awoke from their slumber. Hence, the so-called zombie outbreak has begun.

As reported by the Washington Post, a previous study revealed that anthrax can remain dormant in the permafrost of Siberia for incredibly long stretches of time. There are plenty of cattle burial sites in the region, and many of them threaten to unleash new outbreaks on the world long after they were thought to have died out.

“The spores of Siberian Anthrax remain viable in permafrost for about 105 years,” the scientists wrote in their study. “As a consequence of permafrost melting, the vectors of deadly infections of the 18th and 19th centuries may come back, especially near the cemeteries where the victims of these infections were buried.”

^{Image in text: Spores from anthrax bacteria. Everett Historical/Shutterstock}

Anthrax (Bacillus anthracis) is a relatively common bacteria that can be found in wildernesses all over the world. Symptoms begin between one day and two months after initially contracting the bacterial infection, and takes four different forms: skin, respiratory, intestinal, and intravenous.

Skin (cutaneous) anthrax is considered to be the least dangerous – without treatment, 20 percent of those infected die. Inhalation anthrax, on the other hand, kills around 85 percent of those afflicted by it if they aren’t treated in time. A vaccine is widely available, as are courses of antibiotics for those who have already been exposed to the bacteria.

Anthrax spores take a long time to disappear from the environment, and as such it has been co-opted for use in biological warfare. Its first documented use occurred as far back as 1916, when Scandinavian rebels, supplied by the German Army, used it against Russian forces in Finland in 1916.

It has also been used by terrorists, as seen in the 2001 anthrax attack in the US. Twenty-two people were infected via deliberately contaminated envelopes sent via the postal system, and five died. Anthrax has broken out in Russia multiple times in the past, including in 1979 after an accident at a Soviet biological weapons factory. In the resulting chaos, 64 people died.

^{Nenets, one of the local communities in western Siberia. Vladimir Kovalchuk/Shutterstock}