Over the weekend, the World Health Organization released a disease outbreak report on the events surrounding the death of a Russian infectious disease researcher earlier this month, highlighting that Russia has yet to report a confirmed cause of death. With that “key uncertainty,” the United Nations health agency said it remains impossible to assess the risk of the event or whether the public health measures Russia took were adequate to prevent spread of the unknown disease.

The WHO reported that, so far, it has seen no evidence of ongoing transmission of the mystery disease. “However, confidence in the assessment remains limited by the absence of a confirmed etiological diagnosis, and the remaining uncertainty regarding the source and mode of exposure,” the agency wrote in its report.

The agency laid out the order of events as information trickled out from Russian authorities, noting that it only became aware of the death via media reports on October 2. The WHO subsequently made contact with Russian authorities and requested information on October 3, 6, 7, and 8.

Limited information released

Early media reports indicated that the lab worker had become ill on September 29, possibly following an incident at the lab, the Irkutsk Antiplague Research Institute (APRI) of Siberia and the Far East. Some early reports suggested that the researcher—who was identified by media as 28-year-old Darya Shipilova—died of the plague after breaking a test tube.

On October 2, the Irkutsk branch of Russian health agency Rospotrebnadzor (RPN) said in a statement that a “special sanitary-epidemiological expert commission” had already met over a suspected case of a high-threat pathogen. Sanitary and epidemic control measures were put in place, including identifying, monitoring, and testing all contacts. At the time, RPN said that all contacts had tested negative for high-threat pathogens.

On October 6, Russia’s National Focal Point for the International Health Regulations (NFP) first responded to the WHO’s information requests, saying that no case of plague had been recorded in Irkutsk Oblast. The NFP confirmed that an APRI lab worker had died from a severe case of pneumonia after developing symptoms compatible with an acute respiratory viral infection. The worker was tested for a number of high-threat pathogens, but all the tests had come back negative. Doctors categorized the cause of death as being from pneumonia of undetermined etiology.