The Zombie Virus is an STD
When contemplating the nature of the "Zombie" pathogen, I could not help but encounter the primary problem. The virus, as we knew it, has a horrible transmission vector. Biting is simply not an efficient method of virus transference. There is no way the Zombie Apocalypse could have occured if this method of transmission was the sole, or even the primary, vector for spreading the disease. For a similar example, let's observe rabies. Similar symptoms (though on a far lesser scale), and similar transmission vector. Yet it has not reached near the calamitous scale, rarely spreading beyond a single infected animal or perhaps one infected human when it is spotted.
How then, could a similar virus have taken hold in the population on the scale we have seen with the zombie outbreak? The answer is simple. Bites from the infected were not the primary vector by which the pathogen spreads. We attempted to confirm this by studying the corpses of deceased "zombies", but the cadavers had already suffered so much damage through general neglect that it was impossible to tell the cause of most major trauma.
Still, if we accept this conclusion as valid, we are left with a new question. What disease vector is left? We know the virus isn't airborne, because we have compared its propagation to wind patterns and found mismatches. We have also failed to detect any of the virus capsids in either the air, or the water supplies of the area. Insects also do not seem to be a primary source of contagion, as the majority of the infected have no insect bites on those portions of their skin that remain intact.
Despite the media attention the case received, we already know that the "Patient Zero" case could not have been responsible for the spreading of the virus to the rest of the town. Only two attacks were confirmed, and one of its victims was killed outright, rather than merely infected. How, then, did approximately one fifth of the town come down with the virus in a matter of weeks?
The key breakthrough in determining the nature of the virus's spread lay in discovering the incubation period. Normally, a subject being bitten by one of the infected converts in a matter of days, some lasting up to a week, but no known cases longer than that. Symptoms begin displaying within an hour, and the infection itself is proceeding visibly well within a day.
However, animal testing showed different results. A gorilla or chimpanzee only displays those symptoms that quickly if injected with a rather large dosage of the virus. Injecting small doses typically led to no visible results for several months, one particular subject has actually lasted a year, and has yet to show symptoms. Blood tests taken during this asymptomatic period, however, still definitely indicated that the creature was infected. The virus was spreading and propagating throughout the host, and had infected most tissue and bodily fluids.
The fact that a host to the virus can remain asymptomatic for such a long duration was the key to the virus spreading. It was not the biting of the infected that resulted in the virus spreading, it was the exchange of bodily fluids. Minor cultures of the virus were spread across the population, before anyone even knew there was a new virus to fear. With no symptoms to warn people away, there was noting precluding activities that would result in further contamination. Thus, the ever persistent spread of the virus among the population.
Since the incubation period varies based on how an individual's immune system adapts to fighting the virus, and the amount they were initially infected with, it is impossible to tell how many infected still roam our population, completely unknown, short of rigorous blood testing. We have begun such tests, but this already explains the outbreaks we have had within our camps and facilities. Until the tests are completed, I can only urge caution in any intimate contact you may have with others.
