The World Health Organization says a possible case of pneumonic plague in Russia presents a very low risk outside the country as investigators look into what caused the death of a lab employee there last week.The U.N. health age ncy said Tuesday that it has been in contact with Russian authorities following reports of the death last week of a woman who worked at the Irkutsk Anti-Plague Research Institute of Siberia and the Far East.RELATED STORY | Dozens quarantined after researcher at Russian plague laboratory dies of unknown infectionThe case and the investigation, led by Russian officials, have revived memories of the COVID-19 pandemic and allegations the coronavirus may have emerged at a Chinese lab. WHO has not provided a definitive answer to how the pandemic began.There is currently no indication that we are dealing with anything similar to the pandemic," WHO spokesman Christian Lindmeier told The Associated Press, referring to the woman's illness.Here's what to know about the case and how experts are mobilizing after her death:Pneumonic plague is a form of the disease that affects the lungsThe incubation period for pneumonic plague which means lung-based, and is the most virulent form of the disease can be as short as 24 hours, according to WHO. Its a less common but severe form that can spread between people through respiratory particles.If untreated, the illness can be fatal, but recovery rates are high if detected and treated in time, WHO says.Symptoms include shortness of breath and coughing, often involving the coughing up of blood.The more common form of plague bubonic plague is caused by the bite of an infected flea, and can develop into open sores filled with pus.Pneumonia is a form of acute respiratory infection that is mostly caused by viruses or bacteria, and is spread generally through contact with infected people or from airborne droplets. WHO says pneumonia is the single largest infectious cause of death in children worldwide.What Russian officials are saying about the caseThrough an international health alert system, Russian health officials on Tuesday said a full range of preventive measures had been carried out including tracing of the deceased woman's contacts, medical monitoring and lab tests.Test results showed no presence of dangerous infectious disease pathogens in any of the contacts, said the note from Russian authorities, which was relayed to The Associated Press by WHO."Based on available data, laboratory test results, and health status, medical monitoring for 100% of the contacts has now been concluded," it said. The epidemiological situation is stable and remains under monitoring.The woman died at a hospital in Shelekhov, a town just outside the city of Irkutsk, and its mayor said the hospital was placed under quarantine. The top officials from Russias national public health watchdog traveled to the region Friday.On Monday, Kremlin spokesman Dmitry Peskov advised the public to follow official statements from the watchdog agency, Rospotrebnadzor, rather than rumors or speculation.WHO has mobilized its own experts to look into the caseLindmeier, the WHO spokesman, told a U.N. briefing Tuesday that the institute where the woman worked studies dangerous pathogens, including plague in a part of Siberia where the disease "occurs naturally in wild animals.He said Russian officials have not yet asked for WHO experts to deploy to Russia, where authorities are "looking into whether pneumonic plague caused her death.Russian authorities later told WHO that no case of plague has been recorded in Irkutsk, Lindmeier said.According to the authorities, the womans illness initially presented as a typical acute respiratory viral infection," he said. No case of plague or other high threat pathogen has been found."Trump and Rubio comment on the caseU.S. President Donald Trump said Monday that he was watching the situation with concern and that the United States would be willing to help, though he said he had not spoken to Russian President Vladimir Putin about the case.Asked about Trumps remarks, Kremlin spokesman Peskov said Tuesday that it is always very good when mutual assistance is offered. He wouldnt elaborate further, deferring to Rospotrebnadzor.U.S. Secretary of State Marco Rubio urged Russian authorities to share more information.Maybe theres nothing there. Maybe its bigger than we thought. We dont know, he said at a news conference in Iceland.We encourage Russia to be more transparent and share more information with the world, Rubio said, adding this has so far been quite limited, but hopefully that will change in the next few hours and days.Ian Jones, professor of virology at the University of Reading, said that plague carries a huge history and is still present in many parts of the world, including Russia, although because of modern living conditions and antibiotics, its potential was limited.Dr. Glenn Wortmann, at the MedStar Washington Hospital Center, said the bacteria that cause plague don't travel very far and a person would really need to be face-to-face with an infected person to get pneumonic plague.The chance of this spreading widely in Russia and then extending here to the U.S. will not happen, not with this type of bacteria, because its not spread easily and we have antibiotics to stop it from spreading, he added. ...read more read less