In a report to the US Congress, the Department of Defense revealed that its program of creating artificial biological agents included modifying non-fatal viruses to make them lethal, and genetic engineering to alter the immunology of biological agents to make treatment and vaccinations impossible. The military report admitted that at the time it operated about 130 bio-weapons research facilities, dozens at US universities and others at many international sites outside the purview of the US Congress and the jurisdiction of the courts.
This knowledge hasn't been a secret for a long time. In a classified 1948 report by the Pentagon's Committee on Biological Warfare, the main selling point was that:
"A gun or a bomb leaves no doubt that a deliberate attack has occurred. But if … an epidemic slashes across a crowded city, there is no way of knowing whether anyone attacked, much less who", adding hopefully that "A significant portion of the human population within selected target areas may be killed or incapacitated" with only very small amounts of a pathogen. (1) (2)