The unexplained death this month of a Russian lab technician at a Siberian facility for the study of dangerous pathogens raised global anxieties over the potential for an outbreak of pneumonic plague.

But while the cause of concern - bound up in a lack of transparency from Moscow - was new, Russia’s frozen hinterlands have long been the source of a separate fear that they could harbor disease risks for which the world is not prepared.

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Russian authorities imposed containment measures after the 28-year-old’s death from what they said was pneumonia of “unknown origins,” prompting the United States to ask for more information. A World Health Organization report released Saturday said that Russian authorities ...