One of the greatest scourges the world has ever known is in recent headlines: the Plague. A technician at Russia’s Irkutsk Research Anti-Plague Institute has died of “pneumonia of unknown etiology,” nearly 200 people are under medical observation, and the hospital that treated her has been quarantined. Moscow says there is no evidence of the plague and advises everyone to ignore the rumors. The institute handles some of the world’s most dangerous pathogens, including the pneumonic plague, and Russia has a long history of offensive biological weapons research. In a country where asking questions can be hazardous, few answers have been provided.

To understand the questions now surrounding Irkutsk, it is worth remembering that Russia has been asking a darker question for nearly a century: how can disease be turned into a weapon?

Disease killed more Russians than weapons during the conflicts of the early 20th century, and Soviet scientists began exploring its potential as a weapon. By 1928, the Soviet Union was researching, developing, testing, and manufacturing biological weapons, with the plague emerging as a weapon of particular interest, alongside anthrax and smallpox. In 1937, the deputy director of a Soviet military biological institute died after contracting the plague during research; local authorities contained the incident and prevented an outbreak.

During the Cold War, the Soviet Union expanded its offensive biological weapons program. According to Kenneth Alibek, a former deputy director of the program who later defected to the United States, the Soviet Union maintained roughly 20 tons of the plague and sought to make it more deadly through genetic engineering.

Despiteg the Biological Weapons Convention in 1972, Moscow concealed its program behind civilian research institutions, with the KGB monitoring scientists to prevent leaks. The secrecy extended to accidents: In 1979, authorities concealed an anthrax release from a Soviet biological weapons facility that killed civilians.

Russia officially ended the Soviet offensive biological weapon program in 1992, but many facilities associated with it continued operating as research centers. In 2024, satellite imagery showed new construction and renovations at Sergiev Posad-6, a former Soviet biological weapons site where scientists studied smallpox, Ebola and hemorrhagic fevers. Russian officials describe the work as biodefense research, but the facility does not admit international inspectors.

But Russia’s answer to questions about the history of its own biological weapons programs is usually to question what America is up to instead.

In June, Russia’s Ministry of Defense accused the United States of pursuing biological weapons research in Ukraine, including work involving dangerous pathogens such as the plague.

The accusation follows a pattern dating to the end of the Cold War, when Soviet propaganda claimed that AIDS was the result of a Pentagon biological weapons experiment. Decades later, Russian officials revived similar allegations. In 2018, Moscow’s foreign ministry accused the United States and United Kingdom of separate chemical attacks in Syria, a grotesque inversion of the truth. As COVID-19 spread in 2020, Russia accused the United States of using laboratories in former Soviet republics to develop pathogens. In 2022, Russia blamed the United States for the monkeypox outbreak.

Other outrageous accusations include Russia’s claims at the United Nations that the United States considered delivering biological weapons agents through migratory birds and bats. The Kremlin also insinuated that the United States used blood samples from Ukrainians during the Covid pandemic to create weapons that would selectively target Slavs.

In 2022, Russia took those accusations to the United Nations, alleging that the United States was funding a biological weapons program in Ukraine. The United States and its allies rejected the claims as disinformation.

Secretary of State Marco Rubio has already asked Russia to share more details on the current situation. President Donald Trump said he is planning to discuss the case with Russian President Vladimir Putin “very soon.”On Tuesday, the U.S. Embassy in Russia instructed Americans in the country to “depart immediately.”If Washington is taking the situation seriously enough to issue such warnings, it must be pressing Moscow for the information needed to determine what, exactly, is happening.

The United States should form an interagency team to monitor the outbreak, analyze health data, and determine its cause and extent. Russia should allow U.S. experts to enter and investigate the outbreak. Given that Russia has already accused the United States of the plague bioweapons program in Ukraine, Washington, and in particular, the Defense Threat Reduction Agency should be prepared to counter Russia’s propaganda.

Russia owes the world a clear account of events at the Irkutsk Anti-Plague Institute. If this was simply a case of pneumonia, Moscow should have little to fear from an independent investigation and transparent reporting. When a death occurs at a laboratory handling potential biological weapons, “trust us” is not exactly a substitute for evidence. And if there really is nothing to see in Irkutsk, Moscow could respond by letting someone see it.

Ivana Stradner is a research fellow at the Foundation for Defense of Democracies’ (FDD). Rear Admiral (Ret.) Mark Montgomery serves as senior director of FDD’s Center on Cyber and Technology Innovation (CCTI).