Questions are growing over a possible plague outbreak in Russia after a 28-year-old woman who worked at a laboratory studying the disease died from pneumonia.
Darya Shipilova, an employee of the Anti-Plague Research Institute of Siberia and the Far East in Irkutsk, died earlier this month after developing what was described as mysterious pneumonia.
Her death has raised concern because she worked at a facility where plague-causing bacteria are studied.
The laboratory was locked down after her death, while the hospital where she was treated was quarantined together with institute staff and other people who had been in contact with her.
Russian authorities have released limited information about the case, leaving unanswered questions about what caused Shipilova's illness.
The lack of details has also fuelled speculation about whether she could have been infected with plague.
Pneumonic plague is considered the most serious form because it can progress rapidly. However, experts say all three forms of plague can respond well to antibiotics when treatment is started quickly.
However, there is no confirmation that Shipilova died from plague or that Russia is experiencing an outbreak.
The circumstances surrounding Shipilova's death have therefore become the main focus of concern rather than evidence of a confirmed outbreak.
The secrecy surrounding the case has also reminded some observers of the early stages of the Covid-19 pandemic, when limited information about a new disease contributed to uncertainty and fear.
Experts quoted by The New York Times said the available information does not suggest an immediate threat of widespread transmission.
The case is nevertheless being closely watched because of Shipilova's work at the anti-plague laboratory and the decision to quarantine people who may have come into contact with her.
For now, questions remain over the exact cause of her pneumonia and whether her illness had any connection to the laboratory.
Until more information is released, there is no confirmed evidence of a wider plague outbreak in Russia, despite the growing speculation surrounding the case.
