Why a Russian plague lab death is fueling fears of a cover-up

The death of a 28-year-old worker at a Siberian anti-plague research institute, and the quarantine of nearly 200 people, has fueled speculation of a cover-up, despite Russian authorities’ insistence that she died of pneumonia. CNN’s Matthew Chance reports on why people are skeptical, given the Kremlin’s record during past crises, from Chernobyl to Crimea.