Curse of the Blood Fiends by P. J. Thorndyke

When private detective Rosa Bridger took the case of tracking down a drug-addled starlet for her fiancé’s movie mogul father she figured it would be a simple missing person’s case. But she’s about to stumble over the trail of something much more sinister than the hoodlums and hop pushers she is used to dealing with.

A military research project has spawned a terrifying virus that turns people into monstrous creatures who kill all in their path. When this virus infects a portion of Los Angeles, it’s only a matter of time before the whole city is turned into a bloodbath. Rosa wants answers but there are some who will stop at nothing to cover up the military’s mistake and others still who want to use the virus for their own ends.