Red Lung begins with the onset of flu-like symptoms including fever, aching, nausea, coughing, and fatigue. These symptoms persist for several days and then begin to escalate. Within one week of exposure, necrosis sets into the lung tissue, causing lesions and open sores. This, in turn, results in bleeding into the lungs, causing difficulty breathing, and the bloody coughing that led to the name “red lung.” Once lesions in the lungs begin, they proceed rapidly, ultimately resulting in death, generally within forty-eight hours. Death is most often ascribed to asphyxia from fluid accumulation in the lungs.
Mortality and Contagion
Red Lung is an airborne virus, spread through viral droplet nuclei transmission – minute samples of the virus are transferred when an infected person coughs or sneezes, spreading mucus-coated virus molecules. The comparatively slow progress of the early stages of the virus and the mundane nature of the initial symptoms allowed Red Lung to spread through the population before public health officials could institute policies to curtail travel or quarantine suspected carriers. By the time world governments realized a problem existed, Red Lung was already rampant and spreading throughout all of the industrialized nations.
Before the public health systems crumbled, Red Lung mortality rates were measured at greater than 70%, on par with the worst outbreaks of the Bubonic Plague. The rare cases of recovery conferred immunity on the survivors. This immunity was found to be passed down through genetic bloodlines. Unfortunately, the death rate far exceeded the birth rate, leading to a rapidly declining population.
The Rise of Rabidism
With mortality rates hitting extinction levels, a certain individual within the vampire population revealed his or her existence and immunity to Red Lung. In a desire to protect the vampire food supply—humans--vampire subjects were provided for testing, with the hope of developing a treatment or inoculation for Red Lung.
The efforts at creating a cure with the vampire blood produced disastrous results, leading to the creation of a retrovirus that succeeded in conferring immunity to the Red Lung virus, but only by co-opting the RNA of the host and creating new, altered, DNA strands. These new DNA strands resulted in severely altered physiology, killing the human host but keeping them animated in a state much like vampirism. It also reduced their mental state to one of animal rage, much like a rabid beast.
Eventually, one of the subjects infected with the retrovirus managed to escape (though no one is sure how this happened) and introduced the retrovirus (soon to be called Rabidism) to the broader population. It quickly became apparent that Rabidism was transferable not only to humans, but also had an effect upon the vampire population. Vampires became carriers, immune to the direct effects of Rabidism, but forever imbued with the chance to pass an active case of Rabidism on to any progeny they created.
The Rise of the Vampire Cities
Fearing for their survival, the Master vampires gathered their followers and the remaining uninfected humans and built fortified enclaves. By isolating the survivors and protecting them from the Rabids, the vampires managed to secure their survival. From that point, the regimented system of registration for the humans and careful population control among the vampires arose.