A pathogen is an infectious biological agent that causes disease or illness to its host. While natural pathogens rarely strive to kill their hosts, germ warfare programs revived during the Fall or instigated by the TITANs—sought to modify and use pathogens as a weapon of war. The ideal characteristics of lethal biological agents are highly infectious, have a high potency, low availability of vaccines, and delivery as an aerosol. Most Biomorphs are immune to standard pathogens thanks to their Basic Biomods, and Medichines will protect against most others. However, even these defenses may not protect against diseases left by the TITANs or a new terrorist cell’s biowar bug. It is largely recommended that pathogens be handled as a plot device, rather than an active threat to the characters. Pathogens have no effect on Synthmorphs.