Dean Koontz excerpt from the book
In the book, the virus is a man-made weapon.
"First, it's worth pointing out that in the original 1981 edition of "The Eyes of Darkness," this biological weapon was called "Gorki-400," in reference to a Russian locality. The name of the weapon was changed to "Wuhan-400" when the book was released again in 1989, according to the South China Morning Post." It was changed because the 'cold war' with Russia ended.