Mystery surrounds young worker's death at Russia lab studying severe diseases

GENEVA — The World Health Organization said Saturday it still doesn’t know what caused the death of a young worker at a lab in Russia that focuses on plague and other illnesses.

The U.N. health agency has cited initial, unconfirmed reports suggesting pneumonic plague, a severe disease less common than the better-known bubonic plague linked to the Black Death in the Middle Ages. Pneumonic plague spreads from person to person, causing a severe form of pneumonia, but recovery rates are high if it is detected and treated in time.

WHO, in its first full Disease Outbreak News since the case emerged earlier this month, called for a continued investigation.

Russian health officials, it said, had conducted more than 5,500 tests and found no evidence of any dangerous pathogenic microorganisms.

“Additional clinical, epidemiological and laboratory information, including confirmation of the diagnosis in the deceased laboratory worker, is required to improve confidence in the assessment,” WHO said.

WHO continued to refer to “a purported second case” that, in emailed explanations to The Associated Press, it previously attributed to two tabloid news outlets in Britain and Serbia that cited unspecified reports in Russia.

Russia has denied any such second case.