Image caption, The victim was working at the anti-plague institute in the Siberia city of Irkutsk ByVicky Wong Published 38 minutes ago US President Donald Trump has said he will speak with his Russian counterpart Vladimir Putin soon about the death of a lab worker at a plague research centre in Siberia.
"So far we are in very deep discussions," Trump said, adding that he would be able to report on his talks with Putin "probably" on Thursday.
Russian officials say they are investigating the cause of the 28-year-old's death.
They say that those who came into contact with the victim all tested negative and have not confirmed that the suspected disease is pneumonic plague - a serious lung infection, often described as the most virulent form of plague.
The head of the World Health Organization (WHO) has called for transparency from Russia.
"Timely, complete and transparent information sharing under the International Health Regulations is essential to clarify conflicting reports and enable an accurate assessment of potential public health risks," Tedros Adhanom Ghebreyesus said.
According to the WHO, pneumonic plague has a very short incubation period - sometimes just 24 hours - and can be fatal, if not diagnosed and treated early.
People can be infected through: infected flea bites contact with bodily fluids or contaminated materials the inhalation of respiratory particles Symptoms include shortness of breath and coughing, often with blood-tainted phlegm.
Reports first emerged on Friday of almost 200 people being placed under observation in Siberia's Irkutsk region following the death.
The lab worker, named in Russian media as Darya Shipilova, had reportedly fallen ill a couple of days earlier.
Unconfirmed reports suggested that she had become ill after breaking a test tube containing the pathogen at the Anti-Plague Institute of Siberia and the Far East where she worked - or following a field trip to a region where plague occurs naturally among wild rodents.
But Russian officials have played down those reports.
The country's health watchdog Rospotrebnadzor said the woman had died of "pneumonia of an undetermined etiology".
Ongoing speculation into the lab worker's death has sparked a back and forth between Russia and the US, with questions about a possible spread outside of Russia.
US Secretary of State Marco Rubio said the US had "measures" available to help Russia if the situation turned out to be more serious than claimed.
The bacterium that causes the plague, Yersinia pestis, found among rodents such as marmots in the area.
It killed up to half the population of Europe in the 14th Century when it was known as the Black Death.
It was in response to an outbreak in the 1920s that the Anti-Plague Institute of Siberia and the Far East, was founded just over 100 years ago.
