The WHO's first written assessment finds no sign of onward spread, and still no diagnosis. Russia says observation of every contact ended on 9 October with nothing found.

Per People of Baikal and other Russian media, the laboratory worker breaks a test tube containing Yersinia pestis at the Irkutsk Anti-Plague Research Institute. Russian authorities have never confirmed this, and Rospotrebnadzor later says no such accident occurred.

She is hospitalised in Shelekhov, about 20 km from Irkutsk. People of Baikal says cold symptoms; REN TV and a Telegram channel describe severe pneumonia and a ventilator.

The Shelekhov district hospital's inpatient unit is quarantined, People of Baikal sources say.

The worker dies. The WHO and Irkutsk state television give 2 October; some early Russian-sourced reports said 1 October. Governor Kobzev posts that Anna Popova has convened an extraordinary meeting on a suspected case of a particularly dangerous infection. Mayor Modin says the Shelekhov hospital is under quarantine.

Russian media report at least 197 contacts under medical observation. Buryatia head Tsydenov says the woman had not visited Buryatia. A Telegram channel reports a criminal case over health-safety violations.

The Irkutsk Aluminium Plant in Shelekhov makes masks mandatory as a precaution. Baikalsk's city administration posts, then deletes, a warning against travel to Shelekhov. The WHO asks Russia for information to assess the risk.

Rospotrebnadzor's first statement: the employee had pneumonia of unknown etiology; no microorganisms associated with her work were found; no accidents with pathogenic microorganisms at the institute; the situation in Irkutsk and Shelekhov is stable.

People of Baikal reports three-week quarantines at four Irkutsk hospitals and a maternity hospital, citing a health-care source.

All four named Irkutsk hospitals deny being closed. Hospital No. 1 says no pneumonic plague has been officially confirmed in the city. Newsweek corrects its map story: the WHO has no plague data for Russia for 2019 to 2025.

Popova flies to Siberia for an emergency meeting. Rospotrebnadzor finds two COVID-19 and two rhinovirus cases among contacts and nothing else. The WHO says the public health risk appears to be low. The US State Department says it is aware of reports of a fatal case of suspected pneumonic plague.

Rospotrebnadzor says no plague was detected among contacts. Shelekhov deputy head Elena Sofina says 60% of those observed are released and a dangerous diagnosis was not confirmed. The ECDC reports no secondary cases.

WHO Director-General Tedros: under the International Health Regulations, Russia reported no recent case of plague in Irkutsk oblast and no high-threat pathogens among contacts. The WHO asks for the cause of the pneumonia, the pathogen that prompted the measures, and clarification of media reports of a second employee with pneumonia.

Secretary of State Rubio says it is incumbent on Russia to share more information with the world. The US Embassy in Moscow issues a health alert. President Trump says he has a call scheduled with President Putin.

Rospotrebnadzor: no epidemic risk for Irkutsk; precautionary measures are being wound down; more than 90% of contacts have completed observation after nearly 5,000 tests; the worker had been vaccinated. It still does not say what caused the pneumonia.

WHO Geneva briefing. Maria Van Kerkhove: if this individual did not die from plague, then how did she die? Tedros says the WHO cannot complete a risk assessment and repeats the second-employee question. Reuters finds no Russian media story behind the second-case reports.

Kremlin spokesman Peskov: the vast majority of what the media are reporting is false; no Trump-Putin call has been scheduled, though one could be arranged quickly; Russia informed the WHO per established procedure.

The US State Department confirms it has officially requested additional information from Russia. President Trump, asked about a bioweapon: 'we don't think so'. CDC Director Erica Schwartz: the risk to the US is extremely low.

Mongolia orders health surveillance on its border with Russia and calls the current risk low. Four Central Asian states have border quarantine controls in place. No Trump-Putin call has been reported as having taken place.

Irkutsk Governor Igor Kobzev and Rospotrebnadzor say observation of all of the worker's contacts is complete and nearly 5,000 samples found no dangerous pathogens. Kobzev calls her illness community-acquired pneumonia and says she was vaccinated. Rospotrebnadzor says it has given the WHO full information on the measures taken.

Roskomnadzor, Russia's media regulator, tells outlets to publish only information from official sources on the Irkutsk situation and warns that spreading false information carries liability.

The ECDC's weekly threats report lists the case as pneumonia of unknown aetiology and says the available information is not sufficient to draw a firm conclusion on the risk to the EU population. It is in contact with the WHO's European office.

NPR reports that Russia did not notify the WHO of the death under the International Health Regulations; the WHO learned of it from media, asked for verification on 3 October and received Russia's first reply on 6 October. Two public-health law experts call the response delayed.

Presidents Trump and Putin speak by phone. The White House announces a Russian diesel supply deal; the Kremlin's readout covers Ukraine, Iran and fuel. Neither side's public account mentions the Irkutsk case.

The WHO publishes its first Disease Outbreak News on the case. Russia's report to the WHO: observation of all contacts ended on 9 October with no high-threat pathogen detected; more than 5,500 tests by five Rospotrebnadzor organisations; the panel covered influenza, SARS-CoV-2, other respiratory and bacterial infections including plague; contacts showed only two COVID-19, three rhinovirus and one Haemophilus infection; two independent investigations found no biosafety incident; no further case of severe pneumonia; only the admitting hospital was quarantined; the worker was vaccinated and had not left Irkutsk oblast in the two weeks before she fell ill.

The WHO's own assessment in the same notice: it has not identified evidence of ongoing transmission and advises no travel or trade restrictions. It has not received information identifying the cause, cannot independently judge whether the monitoring period was long enough, and says a laboratory-associated exposure cannot be fully excluded at this stage. It recommends confirmatory testing by reference laboratories and has offered Russia support on laboratory biosafety.