The USA is worried after a worker at a research laboratory in Siberia died. Some newspapers suspect that she came into contact with plague bacteria. She died after developing severe pneumonia. Local reports say she may have broken a test tube of plague bacteria. Officials are checking people who were in contact with the worker. Russia said the woman's death was from "pneumonia of an unknown origin" and not plague. The US secretary of state said there was no "cause for alarm". However, he said officials should "keep an eye on it".

Pneumonic plague can be deadly. It attacks the lungs. It can kill 18 to 24 hours after symptoms begin. It can also spread quickly. It moves from person to person through the air when someone coughs or sneezes. The disease can be treated with antibiotics if they are given as soon as symptoms appear. Pneumonic plague is different from COVID-19, which is caused by a virus and not a bacterium. A microbiologist told the BBC: "Pneumonic plague can spread from person to person, and that is why there is the concern around this."