A lab accident in Siberia released the plague bacteria, killing a researcher and triggering a huge cover-up by Russian authorities.

• A lab technician in Irkutsk, Russia died after accidentally releasing plague bacteria in a secure lab.
• Nearly 200 people who had contact with her were locked down, and a hospital was sealed off.
• Russian officials first admitted the death was linked to plague, then scrubbed the word from reports and blamed "pneumonia of unknown origin" instead.
• Outside health experts say the huge quarantine response doesn't match the official story, suggesting Russia is hiding how bad the incident really was.
• The lab involved is a Soviet-era facility built to study the plague, which still exists naturally in parts of Siberia and Central Asia.

Outlook: The quarantine is expected to be lifted soon, but doubts about Russia's official explanation will likely continue.