The USA has raised concerns after a worker at a plague research laboratory in Siberia died. Some newspapers suspect that she died after coming into contact with plague bacteria. The 28-year-old worker died after developing severe pneumonia. Local reports say she may have broken a test tube containing plague bacteria. Dozens of hospital workers have been quarantined. Officials are monitoring people who were in contact with the woman who died. Russia has said the woman's death was from "pneumonia of an unknown origin" and not plague. US Secretary of State Marco Rubio said there was no "cause for alarm". He said officials should "keep an eye on it".

Pneumonic plague can be deadly. It attacks the lungs and can cause death 18 to 24 hours after symptoms begin. It is highly contagious, so it can spread quickly. It can move from person to person through the air when an infected person coughs or sneezes. The disease can be treated with antibiotics. However, antibiotics work best when 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. COVID-19 spreads much more easily around the world than plague. Microbiologist Dr Simon Clarke told the BBC: "Pneumonic plague can spread from person to person, and that is why there is the concern around this."