I've read all of Koontz books since when he used a pen-name. The book in question is "Eyes of Darkness". The original printing had the virus coming out of Russia but after the fall of the USSR there was a reprint in 1989. In that version the virus comes from a lab in Wuhan and is named the Wuhan-400.

“Wuhan-400 is a perfect weapon. It afflicts only human beings. No other living creature can carry it.” The book states that the biological weapon is called “Wuhan-400” because it was developed at RDNA labs outside of Wuhan.