Could this be because of the leak of yellow cake?
uranium enrichment facility near Isfahan had been leaking radioactive material.

Tehran went to great lengths in December to deny these reports, telling state-run media outlets that “the rumors about leaking and contamination at Isfahan’s [Uranium Conversion Facility] are not true at all.”

November reports indicated that a radioactive leak might have poisoned several workers at the nuclear plant, which converts highly toxic yellowcake uranium into material that could be used in the core of a nuclear weapon.

[link to freebeacon.com]

And this happen the same day that this story comes out


8 DEADLY AGENTS 'TO BRING U.S. TO ITS KNEES'

Millions of lives at stake as Iran develops biological arsenal
Thread: BREAKING INTEL: Iran Genetically Modifies 8 Deadly Bio-Agents to Bring US to its Knees