The United States and the World Health Organisation have asked Russia to provide more information about a suspected case of plague after a laboratory worker in Siberia died from pneumonia of undetermined origin.

The woman, who worked at the Irkutsk Anti-Plague Institute of Siberia and the Far East, reportedly died last week, prompting concerns over whether she may have been exposed to the plague bacterium while handling dangerous pathogens.

Reports on how she may have contracted the suspected infection have varied. One account said she told medical workers that she accidentally broke a test tube containing live bacteria while collecting samples. Another report claimed she had travelled to an area where plague naturally occurs among wild rodents.

However, Russian authorities have rejected reports of a laboratory incident.

Kremlin spokesman Dmitry Peskov described the reports as rumours and speculation, while Russia’s consumer and health watchdog, Rospotrebnadzor, said laboratory tests on material from the woman did not detect microorganisms associated with her work.

The agency also said there had been no emergency or security breach at the institute and that no other infectious disease complaints had been recorded among its employees in the previous 10 days.

However, the Russian statement did not explain what caused the woman’s pneumonia and death or provide details about reports of a second employee suffering from pneumonia of undetermined origin.

US, WHO seek more information

US officials have expressed concern over the limited information coming from Moscow.

US President Donald Trump said on Tuesday that he was scheduled to speak with Russian President Vladimir Putin soon and that his administration was involved in discussions over the incident.

US Secretary of State Marco Rubio said information from Russia remained “quite limited” and urged Moscow to be more transparent.

“Maybe there’s nothing there. Maybe it’s bigger than we thought. We don’t know,” Rubio said.

Rubio also warned that failing to provide relevant information could breach Russia’s obligations under international health regulations.

The US Centers for Disease Control and Prevention said there was currently no indication of a wider threat to the United States but added that it was monitoring the situation closely.

WHO Director-General Tedros Adhanom Ghebreyesus said the organisation had requested further information from Russian authorities, including clarification on the cause of the severe pneumonia, the pathogen that prompted public health measures and reports of another employee with unexplained pneumonia.

He stressed that timely and transparent information sharing was necessary to resolve conflicting reports and properly assess any potential public health risk.

The European Commission also said it was closely monitoring the situation.

Plague is caused by the bacterium Yersinia pestis and is naturally found among some wild rodents, including marmots. The disease was responsible for the Black Death, which killed millions of people in Europe during the 14th century.

Nearly 200 people have reportedly been placed under medical observation following the laboratory worker’s death.