The World Health Organisation (WHO) says it has found no evidence of ongoing transmission linked to the death of a Russian laboratory worker who developed severe pneumonia.
In a disease outbreak report published on Saturday, the organisation said Russian authorities reported that tests conducted on the deceased worker and her identified contacts detected neither plague nor other tested high-threat pathogens.
The worker, who was employed by the Irkutsk Antiplague Research Institute of Siberia and the Far East, died on October 2 after being admitted to hospital with severe pneumonia on September 29.
Her death raised concerns about a possible pneumonic plague infection following media reports of occupational exposure at the laboratory.
However, Russian authorities said she died from pneumonia of undetermined etiology after testing negative for several high-threat pathogens.
The WHO said it had not received information identifying the agent responsible for the fatal illness, meaning the cause of her illness remained unknown.
The organisation added that laboratory-associated exposure could not be completely ruled out, although available information did not indicate infection with the tested high-threat pathogens or identify any additional linked cases.
Nearly 200 people were reportedly placed under medical observation following the death as Russian authorities introduced precautionary measures, including contact tracing and laboratory testing.
According to the WHO, more than 5,500 laboratory tests were conducted, with none detecting high-consequence or dangerous pathogenic microorganisms.
Russian authorities informed the global health body that the seven-day medical monitoring of identified contacts, which included daily laboratory testing, was completed on Friday.
“Test results were negative for the tested high-threat pathogens. All contacts had been medically followed up in healthcare facilities or at home, and all remained asymptomatic throughout. Quarantine measures were instituted in the hospital where the patient was being treated,” WHO said the National Focal Point (NFP) reported.
The authorities also said the deceased worker had been vaccinated against the high-threat pathogens she handled as part of her work and had not travelled outside Irkutsk Oblast in the two weeks before her symptoms began.
Russian officials said investigations found no laboratory biosafety or biosecurity incidents at the institute, contradicting media reports suggesting otherwise.
The case had earlier attracted international attention, with the United States and the WHO seeking further information from Russia amid uncertainty over the suspected infection.
In its latest assessment, the WHO said the absence of a confirmed diagnosis limited its ability to independently evaluate the public health risk.
It added that further clinical, epidemiological and laboratory information was needed to establish the cause of the illness and increase confidence in the assessment.
The organisation said it would continue monitoring the situation and did not recommend any travel or trade restrictions related to the incident.