This is an examination of how the zombie virus could develop naturally, as a result of mutation, and how the transmission can occur from animal to human. This will be based off of current potential viruses that could cause pandemics, and through these pandemics, the development of the zombie virus would naturally occur. Please note that this is discussed in context of science of parasitology.
Evolutionary Mechanisms Needed to Occur
For natural mutation to occur, obviously there will need to be at some point an exchange of genetic material. The viral mechanism of delivery into host cells and replication generates mutations in the virus, particularly if there are more available hosts. Additionally, a catalyst or set of catalysts, either through the environment or internal change in body chemistries for example, must propel the viral strain(s) to jump from one host (animal) to another (human) for its own benefit, propagation and survival. It should be noted that some strains of viruses from animals are already pathogenic to humans: the avian flu, mad cow disease and others, and these viruses could potentially and quite easily become the source of mutation for a zombie virus. Lastly, the strain of virus must not be easily capable of being eradicated or otherwise disabled during its evolution and transmission while in its new host (human). In other words, the mutant zombie virus must find the human host a hospitable environment to live and thrive.
This is a selection of the current viruses which a zombie virus can develop from and an examination of each, as follows. In the following, the definitions of reservoir, vector and host are from parasitology and not any of the other biological or physical sciences. Reservoir is an alternate or passive host that harbors pathogenic organisms without injury to itself and serves as a source for which other organisms can be infected. Vector is a carrier, often an arthropod, that transmits an infective agent from one host to another. Host is an organism that is directly infected with or is fed upon by a pathogenic organism. Unlike the reservoir, the host is harmed by the association with the pathogenic organism.
There could be possible transmission from birds to humans, but the possibility of a host directly from poultry to human would be unlikely. It would be unlikely due to the fact that most poultry is cooked before being eaten. However, the transmission during the partially automated process in slaughterhouses to humans could be potentially possible. Due to some manual labor involving illegals or underpaid minorities, the sanitation of slaughterhouses might not be as well kept as some may think. It may not be Upton Sinclair’s The Jungle anymore, but these slaughterhouses have shown little improvement recently. With even a minor infection from the raw poultry, these slaughterhouses could become potentially ground zero for a disastrous outbreak whereby these illegal workers serve as hosts.
However, fish might be potential reservoirs for humans whereby infected humans and animals serve as hosts. In the meantime, mosquitoes and other bugs might become vectors, transporting the mutant virus worldwide.
The avian flu itself, as well as some of the other viruses listed below, should be noted that the virus itself does not necessarily have to remain with the preferred host. In some cases, these strains are also pathogenic to humans — most notably, the H5N1, H7N3, H7N7 and H9N2. The flu itself when contracted to a human will not spread easily to another as it requires prolonged contact. In order for the perfect zombie virus to develop from the avian flu, the virus would have to develop more efficient infection mechanism, and that could only happen with mutation from either human or bird genes. Recently, the avian flu virus has begun mutating, mostly acquiring its genetic code from birds rather than humans. Although vaccination has worked on the lesser pathogenic strains of avian flu, should a lethally pathogenic virus develop, no amount of current vaccines would prevent a massive pandemic. It’s not like it hasn’t happened before, and should it transform into a zombie virus, it will become a worldwide pandemic easily.
Unlike the avian flu, mad cow disease, otherwise known as bovine spongiform encephalopathy (BCE), is a fatal neurodegenerative disease that attacks the brain and spinal cord. In some ways, the infected cows resemble the human zombies in horror movies in their physical and mental instability — and resembles rabies which will be discussed later. BCE is a transmissible spongiform encephalopathy (TCE) which means that healthy tissue can become infected from tainted tissue. This disease then infects the brain, causing holes with symptoms of physical and mental degeneration, ultimately leading to death of the host.
The origin of this fatal disease can be traced to a mutation in scrapie in sheep, a variant of the virus, or quite possibly from earlier times that affected bovine alone. The disease can be traced as far back as 4th and 5th century AD.
When acquired by humans, it is known as new variant Crutzfeldt-Jakob disease, and the outbreak in 2009 when it killed 166 people in the UK and 44 in other nations.
One should note that the virus can withstand high temperatures of cooking. This could be a potential boom for something like the a mutant zombie virus to take advantage of. In other words, by simply burning the individual infected, as shown in some zombie movies, the virus itself can still survive and can still infect others in its wake. This virus would one of two viruses that can easily transform into a mutant zombie virus, and if it does, it could cause a worldwide pandemic easily as it is not easily eradicated and somewhat transmissible from host to host.
The infectious agent human immunodeficiency virus (HIV) that causes AIDS, otherwise known as acquired immunodeficiency syndrome, could potentially develop into a zombie virus as well or minimally, the precursor to a zombie virus infection.
The symptoms of HIV/AIDS includes the crippling of internal organs due to infections from bacteria, viruses, fungi and parasites that would otherwise be resisted by a healthy immune system. Although presently treatable via anti-retroviral therapy, presently, there is still no known cure or vaccine.
Although HIV/AIDS is considered a pandemic as it has affected 33.3 million people worldwide in 2009, I believe the potential for a mutant zombie virus to develop from this agent would be difficult as new medications are constantly in development and the method of transmission. Although easily adaptable between humans, it does not directly affect physical or mental capacities directly. Rather, it is the gateway that allows opportunistic infections to occur. Should a zombie virus develop in concurrence with HIV/AIDS, those infected with HIV/AIDS would surely become some of the first to become zombies since their immune systems offer little resistance and give the virus the opportunity to spread worldwide.
This is perhaps one of the natural and easiest development of a virus transforming into a zombie virus. It will most likely develop in the Philippines and the Far Eastern Basin, should such a virus occur similar to the book World War Z. Rabies is a virus that causes acute encephalitis and attacks the central nervous system (CNS) of mammals. If left untreated with vaccines, after it has attacked the nervous system, this disease is often fatal within three to five days. The symptoms of this disease includes malaise, headache, fever, mania, coma and ultimately death.
Although treatable, it kills about 55,000 per year, residing in mostly Africa and Asia. Due to the medicine available and sanitation procedures in these regions of the world, rabies, with its proclivity to spread between mammals, could potentially become the natural source for a zombie virus to develop and mutate as it develops resistance against medicines and treatments. Should a zombie virus develop from rabies, it could spread fast in Asia and Africa and then spread to developed countries.
Human Flu Virus (Influenzavirus B)
The human flu would appear to be the easiest mutation as the transition from a natural human virus to a zombie virus would not require little mutation. Majority of human flu virus pandemics have arisen from mutations in the genetic code of the virus from other animals, including pigs and poultry. The H5N1, a strain of avian flu described above, is one such recent example.
However, for this topic in discussion, I am discussing Influenzavirus B, or those viruses limited to humans. Influenzavirus B mutates at slower rates than Influenzaviruses A, which affect poultry, and Influenzavirus C, which affect humans, dogs and pigs. Also with its restrictions on only humans, it has limited ability to cause a pandemic and mutate into a zombie virus. Additionally, in developed countries, vaccinations are created as new strains of the virus appear. Antiviral drugs are also available to to treat those already infected. Influenzavirus B, although it has appearances of a potential zombie virus candidate, really isn’t much of a threat.
This has been an examination of all current viruses and their potential for mutating into a zombie virus. Rabies, mad cow disease and avian flu are three top potential candidates in my honest opinion. They are susceptible to mutation, pandemics and somewhat resistant to medications and vaccines. All three are capable of being fatal as well.
This may be the stuff of storybooks for now. As these viruses mutate throughout the years, one unfortunate mutation, combined with the gradual resistance to present vaccines, could turn into a zombie virus pandemic. However, this isn’t Judgement Day quite yet…