Bio is very easy, especially with a suicide volunteer who is willing to travel to the US aboard a commercial aircraft and fly airlines internally until he becomes so sick he is no longer ambulatory.
Airliners, subways, trains simply are big petri dishes, and with our hub-and-spoke airlines system, freshly contaminated people spread it over and over again.
And if you move into the area of weaponized viruses, it gets 100 times worse.
Suggest reading “The Cobra Event.” It is fiction, but written by an expert on Ebola, Rift and other hemorrhagic diseases.
Fear mongering is expected to occur within the next 5 mins as well.