
US President Donald Trump was asked by reporters about the situation in Russia, where the plague is suspected to have spread after the death of a laboratory worker in Siberia.
Trump has declared that the US will help Russia while emphasizing that the microbe is now stronger than it was before.
"This is a disease that we used to be able to control. But, somehow, those microbes have become stronger and smarter. They are like an army. We will help Russia," he said.
A 28-year-old employee at the Anti-Plague Institute in Irkutsk, Siberia and the Far East, fell ill and died from what is suspected to be a case of pneumonic plague.
Rospotrebnadzor, Russia's consumer watchdog, has not confirmed the exact cause of death, saying only that the employee died of "pneumonia of unknown etiology." More than 200 people have been placed under observation following her death.
He added that no microorganisms related to her professional activities were identified in the sample from the deceased patient.
Irkutsk region governor Igor Kobzev said authorities had identified, examined and placed under medical observation all people who had come into contact with the patient. No other employee at the anti-plague institute had visited the doctor in recent days, he added.
Plague is an infectious disease caused by the bacterium Yersinia pestis, usually found in small mammals and their fleas, according to the WHO. It has been absent from Europe for more than 50 years, although it continues to occur in the Americas, Africa and Asia.