Darya Shipilova's death at a Siberian plague research institute triggered quarantines and mass observation, but Russia has not confirmed what killed her.
https://www.foxnews.com/world/mystery-death-russian-plague-lab-triggers-sweeping-precautions-us-watches-closely
https://www.foxnews.com/world/mystery-death-russian-plague-lab-triggers-sweeping-precautions-us-watches-closely