[UPDATE] Trump says he will call Putin about a Siberian plague-lab worker's death; Russia says tests have not linked it to plague

Washington is preparing a formal request for information, and the State Department reissued its Level 4 do-not-travel warning for Russia.

Daria Shipilova, 28, a worker at a Siberian anti-plague institute, died of what Russia officially calls pneumonia of unknown cause. Russian authorities say tests have not linked her death to plague. Russia's response. About 200 people are under quarantine or medical watch, and at least five hospitals remain quarantined. Testing of her contacts found two Covid cases and one rhinovirus case, and no plague. The U.S. response. Washington first contacted Moscow as early as Friday, Oct. 2, and is now preparing a formal request for information. The CDC says there is no sign of a broader threat to the United States. Secretary of State Marco Rubio, speaking in Iceland, said: "Maybe, you know, there's nothing there. Maybe it's bigger than we thought. We don't know." Still open. What pathogen killed her, and whether anything escaped the lab.

PREVIOUSLY

By Oct. 6, a 28-year-old worker at an anti-plague institute in Siberia had died. Russia called the cause pneumonia of undetermined origin. It quarantined a hospital and put nearly 200 contacts under watch. Trump offered U.S. help.

What the U.S. would add if Washington escalates:

Next step: a CDC travel health notice for Russia, on top of the State Department's Level 4 warning
Then: Customs and Border Protection rules for screening sick travelers at U.S. entry points
The playbook comes from David Mansdoerfer, a former Trump health official, who calls it "very well defined"