In 1991, the Soviets abandoned anthrax island, a bioweapon facility which still has over 90% chance of killing people decades after its creation

For decades during the Cold War, a remote island in the middle of the Aral Sea hid one of the Soviet Union’s most secretive and dangerous military projects. Known as Vozrozhdeniye Island (meaning “Rebirth Island” in Russian), the isolated location served as a major open-air testing ground for the Soviet biological weapons programme. When the Soviet Union collapsed in 1991, the military abandoned the site, leaving behind deserted laboratories, contaminated areas and buried stocks of one of the world’s deadliest biological agents: weaponised anthrax.

Even decades after its creation, anthrax remained a terrifying threat because its spores can survive in harsh environmental conditions for extremely long periods. Unlike many biological agents that quickly die outside a host, Bacillus anthracis forms durable spores capable of remaining viable in soil for years or even decades. Inhalation anthrax is particularly deadly, with historical untreated fatality rates often exceeding 90%.

The secret Soviet city of Aralsk-7

The Soviet Union established the facility on Vozrozhdeniye Island in the 1950s, creating a secret military settlement known as Aralsk-7. The isolated outpost housed scientists, military personnel and their families, with a population estimated at around 1,000 people at its peak. The town contained laboratories, barracks, schools and basic infrastructure, but its true purpose remained hidden from the outside world.

The island’s remote location in the Aral Sea made it ideal for biological weapons experiments. Surrounded by hundreds of kilometres of water and far from major population centres, Soviet planners believed accidental releases could be contained. The site was used as an open-air proving ground where biological agents were tested under field conditions.

According to the Nuclear Threat Initiative (NTI), Vozrozhdeniye Island operated as the Soviet Union’s major biological weapons testing site from 1936 to 1992, with the most intensive activities occurring during the Cold War. The facility tested pathogens including anthrax, plague, Q fever, tularemia, smallpox and Venezuelan equine encephalitis, as well as biological toxins such as botulinum toxin.

Why anthrax made the island dangerous even after abandonment

While many pathogens degrade quickly once outside laboratory conditions, anthrax presents a unique danger. The bacterium can transform into spores, dormant structures that resist environmental stress, heat and chemical exposure.

The Soviet Union reportedly transported large quantities of anthrax material to Vozrozhdeniye Island for disposal during the final years of its biological weapons programme. Some reports have described the island as one of the world’s largest anthrax burial sites.

Unlike conventional contamination, anthrax spores do not simply disappear when a facility is abandoned. They can remain embedded in soil and potentially become a threat if disturbed by humans, animals or natural processes.

The Guardian reported that anthrax was the major exception among biological agents tested at the site because its spores could persist far longer than other microorganisms. The report noted that if anthrax spores enter the lungs, infection can have a fatality rate greater than 90% without effective treatment.

The 1971 smallpox outbreak that exposed the island’s deadly risk

The dangers of Vozrozhdeniye Island were not limited to theoretical fears about abandoned biological weapons. In 1971, a mysterious smallpox outbreak struck Aralsk, a city on the northern shore of the Aral Sea, killing three people and infecting several others.

Decades later, researchers suggested that the outbreak may have been connected to a Soviet biological weapons field test conducted on Vozrozhdeniye Island.

A 2002 report published in the journal Science examined evidence surrounding the outbreak and raised concerns that the cases were linked to biological weapons experiments at the island facility. The report cited accounts that a research vessel had travelled unusually close to Vozrozhdeniye Island during the summer of 1971, despite restrictions preventing ships from approaching the site. A woman working on the vessel later developed smallpox, and the disease subsequently spread to people in Aralsk.

The collapse of the Soviet Union left a dangerous legacy

The Soviet withdrawal from Vozrozhdeniye began in 1991 after specialists left and laboratories were closed. Following the dissolution of the USSR, newly independent Kazakhstan and Uzbekistan inherited responsibility for the abandoned site.

In 1992, Russia formally ordered the closure of offensive biological weapons programmes and stated that remaining structures at Vozrozhdeniye would be dismantled and the area decontaminated. However, the remote location and political uncertainty created concerns about whether the site could be properly secured.

The abandoned military town of Kantubek became a ghost settlement. Buildings, laboratories and equipment were left behind as the population disappeared. Over time, scavengers entered the area searching for scrap metal, raising fears that contaminated materials could be disturbed.

The Aral Sea disaster exposed the hidden danger

One of the biggest problems facing Vozrozhdeniye Island was not only what had been buried there, but what was happening around it.

The Aral Sea, once one of the world’s largest inland bodies of water, dramatically shrank during the Soviet era because rivers feeding it were diverted for agricultural irrigation. As water levels fell, Vozrozhdeniye expanded in size and eventually became connected to the mainland.

The isolation that had protected the Soviet facility was disappearing.

By the late 1990s and early 2000s, officials feared that easier human access, animals moving through the region and possible industrial activity could disturb contaminated areas. The drying sea transformed a remote island into a more accessible landmass, increasing concerns over biological security.

The US-led cleanup operation after 9/11

Concerns intensified after the September 11, 2001 terrorist attacks and the anthrax attacks in the United States that same year. Washington feared that unsecured Soviet-era biological sites could become targets for groups seeking dangerous pathogens.

In 2001, the United States and Uzbekistan reached an agreement under the Cooperative Threat Reduction programme to help secure and decontaminate the site. The project focused on destroying remaining anthrax spores in burial pits, dismantling abandoned biological weapons infrastructure and reducing the risk of proliferation.

The operation, carried out in the early 2000s, involved dismantling parts of the former laboratory complex and treating contaminated areas, including anthrax burial locations.

However, experts have continued to debate the long-term effectiveness of such cleanup efforts because eliminating every anthrax spore from a large contaminated environment is extremely difficult.

A Cold War warning buried in the desert

Today, Vozrozhdeniye Island is no longer the secret military installation it once was. The laboratories are abandoned, the town of Kantubek is empty, and the Soviet biological weapons programme is a chapter of Cold War history.

Yet the site remains a reminder of the dangers created by large-scale biological weapons research. A location once chosen because it was isolated became vulnerable when environmental changes and political collapse removed that isolation.