WHO uncertain what caused pneumonia that killed Russian plague lab worker

The World Health Organization said on Saturday that it still does not know what caused the pneumonia that killed a Russian lab worker at an anti-plague research center in Siberia this month, and that no case of plague had been registered.

The WHO said the Russian state regulator reported that tests of the lab worker and those who came in contact with her were negative for the high-threat pathogens tested, that her contacts still showed no symptoms, and that no further linked cases of severe pneumonia had been identified.

"Based on the information provided ... (the) WHO has not identified evidence of ongoing transmission associated with this event. A key uncertainty remains the absence of a confirmed diagnosis in the deceased laboratory worker," it said in a statement.

The lab worker fell ill and died in undisclosed circumstances on October 2, prompting authorities to quarantine about 200 people and causing public health fears on social media.

Global health officials have been extra alert to fatal pneumonia cases of undetermined cause since the COVID-19 pandemic, which began with a cluster of fast-spreading fatal respiratory illness in China. The cause of individual pneumonia cases can often not be determined.

Russian authorities have said the lab worker was appropriately vaccinated and that they found no microorganisms linked to her work in her body.

On Thursday, Russia said it had completed health checks on all the worker's contacts. It says it had provided full information to the WHO according to established procedures.

-Reporting by Gnaneshwar Rajan in Bengaluru and Alessandra Prentice; Editing by Edmund Klamann and David Gregorio/Reuters