US President Donald Trump says he will speak to Russian President Vladimir Putin about reports surrounding the death of a laboratory technician at a plague research institute in Siberia.
The reported death has prompted calls from Washington and the World Health Organization for greater transparency from Moscow, although Russian authorities have denied that plague-related emergency measures are in place.
The 28-year-old woman, identified by Russian media as Darya Shipilova, reportedly died last week after an incident at a research facility in the Irkutsk region.
Local media have reported that she may have contracted pneumonic plague after a test tube broke, while other reports have suggested her death could have been linked to a laboratory accident.
One report claimed that as many as 200 people who may have been in contact with the woman were placed under quarantine.
However, Russia's consumer and health watchdog, Rospotrebnadzor, has rejected reports that special anti-plague measures had been introduced.
The agency said an online document circulating about the alleged measures did not originate from an official source and was false.
Russian officials have also said postmortem testing did not detect plague.
Irkutsk Regional Governor Igor Kobzev said a Rospotrebnadzor investigation found that the woman had died from pneumonia, although the exact cause remained undetermined.
He said no microorganisms connected to the woman's work had been detected in her biological samples, and no other employees at the institute had sought medical attention following her death.
The WHO said Russia had informed the organisation that no cases of plague had been recorded in Irkutsk.
However, WHO Director-General Tedros Adhanom Ghebreyesus called for further information from Moscow amid conflicting reports.
He said timely and transparent information sharing was necessary to assess any potential public health risks accurately.
US Secretary of State Marco Rubio also urged Russia to provide more information.
“We encourage Russia to be transparent and share more information with the world so that all of us could react accordingly and appropriately,” Rubio said during a visit to Iceland.
Trump later confirmed that he had a call scheduled with Putin and said the conversation would take place “very soon”.
Asked about US intelligence assessments, Trump said Washington was engaged in “very deep discussions” and that more information could be made public.
The Wall Street Journal reported that the US State Department had sent Moscow a confidential diplomatic communication warning that failing to provide details could conflict with Russia's international health obligations.
Plague is a bacterial disease that can occur in several forms. Pneumonic plague affects the lungs and can spread through respiratory droplets, while bubonic plague is generally transmitted through infected fleas.
According to the WHO, pneumonic plague can be fatal if treatment is not started early.
Trump said he was prepared to offer assistance to Russia if necessary. In response, Rospotrebnadzor said Moscow was also willing to help the United States address infectious disease outbreaks.
The Russian agency pointed to rising measles cases in three US states and a fatal plague case reported in New Mexico in June.
Meanwhile, an international conference on plague and other infectious diseases is scheduled to take place in Irkutsk on October 21 and 22.
Organisers have stressed that the conference was planned independently and is not connected to the recent death of the anti-plague institute employee.