Trump told reporters outside the White House on Monday that the United States would step in to support Russia after a laboratory worker at a plague research institute in Siberia died, prompting authorities to quarantine dozens.
He described the outbreak as a "big problem" for Russia and added that "it's a rough disease" after noting the scene.
Russian officials said the situation was under control, but the death sparked fears on social media.
Despite tensions over Ukraine, Trump said he could work with President Vladimir Putin and that the U.S. would help any country facing such a problem.
The White House will coordinate with Russian health authorities to deliver diagnostics, protective gear, and training for laboratory staff.