Ricin: A weapon of assassination rather than mass destruction

Today it was reported that the Pentagon mail facility received two pieces of mail Monday that initially tested positive for the toxin, ricin. CNN reports that the letters were addressed to Secretary of Defense James Mattis and to Chief of Naval Operations, Admiral John Richardson. It was latter reported that one piece of mail was also addressed to President Trump. To answer some questions about ricin is Senior Scholar at the Johns Hopkins University Center for Health Security, Amesh Adalja, MD.