description | Virally encoded toxin that acts as a host virulence factor against another organism. Viral exotoxins are mostly expressed from integrated viral genomes. Bacterium host, bacterial populations, and the encoding virus/provirus probably benefit from the expression of such exotoxins Although prokaryotic viruses can kill their host if they switch to the lytic cycle, provirus encoding exotoxins (e.g. shiga toxin, diphtheria toxin) are often retained for the sake of bacterial utility |