What is pneumonic plague, and should you be worried?

Specialists work in a laboratory as part of anti-epidemic measures during the 2019 Winter Universiade in Krasnoyarsk.

Years after Covid-19 brought the world to its knees, we have reports of a suspected case of pneumonic plague in a laboratory worker in Russia. This raised concerns and questions about the disease, how it spreads and how dangerous it is.

The World Health Organization (WHO) has asked Russia for further information after media reports emerged about the death of a worker at the Irkutsk Antiplague Research Institute in Siberia.

The worker died after being hospitalised with severe pneumonia. Initial reports suggested the illness may have been pneumonic plague following a possible accidental laboratory exposure.

However, WHO said it does not yet have enough information to conduct a full risk assessment.

Russian authorities have said that no recent case of plague had been reported in the Irkutsk oblast and that around 200 contacts had been placed in quarantine.

The authorities have also said that people who had contact with the researcher tested negative for pneumonic plague.

When we think of a 'plague', our minds often go to the bubonic plague. However, pneumonic plague is a severe form of plague that affects the lungs.

Plague is caused by the bacterium Yersinia pestis , which is generally found in small mammals and their fleas.

There are three main forms of plague namely: bubonic plague, which affects the lymph nodes, septicaemic plague, which occurs when the bacteria infect the bloodstream and pneumonic plague, which affects the lungs.

According to the US Centers for Disease Control and Prevention (CDC), pneumonic plague is the most serious form of plague and is the only form that can be transmitted directly from person to person.

Pneumonic plague can develop when untreated bubonic or septicaemic plague spreads to the lungs.

It can also occur when a person inhales infectious droplets released when another person or animal with pneumonic plague coughs.

Plague bacteria are usually transmitted to humans through infected fleas or contact with infected animals.