Russia's Suspected Plague Case Sparks Confusion Over Bubonic and Pneumonic Forms — What We Know So Far

The unexplained death of a laboratory worker at a Russian anti-plague research institute has revived fears about a disease most people associate with medieval history. But as concern spread online, so did confusion over whether plague was involved and, if so, whether it would be the bubonic or pneumonic form.

Some social-media users declared that the 'bubonic plague is back,' while others claimed the concern was actually pneumonic plague, sometimes accompanying those claims with alarming and inaccurate statements about its mortality and ability to spread.

However, there is one important distinction before either label is applied: Russian authorities have not confirmed that the laboratory worker died from plague.

What Happened to Darya Shipilova?

Darya Shipilova, identified by Russian media as a 28-year-old laboratory worker, worked at the Irkutsk Anti-Plague Research Institute of Siberia and the Far East. She was hospitalised in late September and died on 2 October after developing severe pneumonia.

Russia's health watchdog, Rospotrebnadzor, has described the cause as pneumonia of unknown origin. The agency also said no microorganisms associated with Shipilova's professional activities were detected.

The circumstances prompted precautionary measures. Russian authorities identified 197 people who may have come into contact with Shipilova, with 189 reportedly hospitalised for medical observation.

The World Health Organisation (WHO) said Russian authorities reported that no recent cases of plague had been registered in Irkutsk Oblast and that no high-threat pathogens had been detected among identified contacts. WHO has requested further information about the cause of Shipilova's severe pneumonia, the pathogen that prompted the public-health measures and reports of another employee with pneumonia of undetermined cause.

'The Bubonic Plague Is Back'

The uncertainty quickly spilled onto social media.

'I see the Bubonic plague is back,' one Threads user wrote, joking that of all the futuristic ways things could go wrong, 'plague it is.'

Others attempted to correct the claim.

'Nah, it's pneumonic plague that's put the band back together, not bubonic,' another user wrote. But the same post went on to claim that pneumonic plague has a 100 per cent mortality rate and must be detected within 24 hours, illustrating how attempts to correct misinformation can introduce inaccurate or oversimplified medical claims of their own.

Another post similarly warned people who thought the reports involved bubonic plague that the illness was allegedly pneumonic plague, while contrasting purported fatality rates for the two forms.

Bubonic vs Pneumonic Plague

Bubonic and pneumonic plague are not separate diseases caused by different pathogens. They are different forms of plague caused by the bacterium Yersinia pestis.

According to the WHO, bubonic plague is the most common form and is usually caused by the bite of an infected flea. It is characterised by swollen, painful lymph nodes known as 'buboes.'

Pneumonic plague, meanwhile, affects the lungs and is the most virulent form. Unlike bubonic plague, it can spread between people through respiratory particles from an infected person. Antibiotics are effective against plague when treatment begins early.

That distinction matters because references to the 'Black Death' or claims that bubonic plague itself is spreading between people can give readers a misleading picture of the current concern.

Is There a Plague Outbreak in Russia?

As of 7 October, there is no confirmed plague outbreak in Irkutsk, and Russian authorities say there is no risk of an epidemic.

Rospotrebnadzor said testing among Shipilova's contacts identified two COVID-19 infections and two rhinovirus infections, with no other infectious-disease pathogens detected.

The investigation and international monitoring continue. For now, however, describing the incident as a confirmed case of either bubonic or pneumonic plague goes beyond what Russian health authorities and the WHO have established.