Russian authorities said today that no ‘pathogenic microorganism’ was detected in the medical tests carried out on everyone who had been in contact with an employee of a Siberian institute that researches plague.

Daria Sipilova died in unexplained circumstances on 2 October.

‘Medical monitoring of all those who came into contact with the patient has been completed. No health problems linked to an infectious disease were detected,’ Igor Kobzev, governor of the Irkutsk region, where the institute is based, announced on the messaging app Max.

According to Kobzev, almost 5,000 laboratory tests were carried out and no dangerous pathogen was found.

The woman’s death prompted fears that she and her contacts may have been infected with plague. Kobzev confirmed today that the 28-year-old researcher died of pneumonia unrelated to her work. He also stressed that Sipilova ‘had been vaccinated and was immune to the dangerous pathogens she worked with’, and that she followed ‘the required control measures’ when handling such microorganisms.

‘No emergency linked to the handling of pathogens was identified inside the institute,’ he added.

The US, the European Union and the World Health Organization had called on the Russian authorities in recent days to provide more information about her death.

Kremlin spokesman Dmitry Peskov claimed yesterday that most of the information reported by the media about the death was ‘false’.

Russia’s health watchdog, Rospotrebnadzor, had earlier said that post-mortem tests on the woman’s body led to the conclusion that she died of ‘pneumonia’ of undetermined origin.

Plague is an infectious disease caused by bacteria. According to the World Health Organization, pneumonic plague is extremely contagious and can be fatal if not treated quickly.