World Health Organization: no sign of spread from the Siberia plague-lab worker's death, but the cause is still unknown

The worker was hospitalized with severe pneumonia on Sept. 29 and died on Oct. 2. In a report on Saturday, the World Health Organization said Russia's official contact point had confirmed the death. Russia said no case of plague had been registered recently in the Irkutsk region, and that the worker and everyone in contact with her had been tested for a range of germs, including the most dangerous ones. Those tests came back negative. Her contacts were watched in hospitals or at home, and none got sick.

Russian authorities also told the organization that no biosafety incident happened in the laboratory, contrary to media reports. The death is now classed as pneumonia of undetermined cause.

The organization was careful about what it does not know. It has not been told what germ caused the illness. Without that, it says, it cannot judge whether contacts were watched long enough to rule out every possible cause. Because she worked with dangerous pathogens, it says, an exposure in the lab cannot be fully excluded. It will keep monitoring.