Those of you who have followed my writing over the past decade know that I blog extensively on medical topics. I began with the COVID epidemic and then moved on to cancer and cerebral aneurysms. In this post, I’d like to discuss what I call the theory of disease. There are all sorts of diseases in this world, and no species of plant life or animal life is immune. Some animal diseases, such as Parvo or heartworms, cannot be passed on to humans. Similarly, some human diseases, such as HIV or typhoid fever, cannot be transmitted to critters. Other diseases can cross the species barrier. These diseases may be fungal (such as ringworm), bacterial (e.g., tuberculosis), or viral (as in COVID).
Let me focus in this post on viruses and common carriers of viruses. Specifically, how a young bat on another continent can contract a deadly virus that eventually makes its way to your home and what may follow.
Viruses
Let’s look at viruses. The Cleveland Clinic has a convenient, easy to understand definition of a virus:
Viruses are microscopic organisms that can infect hosts, like humans, plants or animals. They’re a small piece of genetic information (DNA or RNA) inside of a protective shell (capsid). Some viruses also have an envelope. Viruses can’t reproduce without a host. Some common diseases caused by viruses include the flu, the common cold and COVID-19.
Notice that a virus cannot independently reproduce without the help of another living cell. This important function leads many to conclude that a virus is not truly alive, although other authorities speak to it as if it were alive.
We also need to touch however briefly on Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA). DNA is a biopolymer molecular material which has a ladder-like helix containing the genes of the plant or animal. It is considered to be the “master blueprint” for that species of plant or animal. The RNA has what is thought to be a “working” or “draft” copy of the master blueprint found in the DNA. When the cells in the DNA replicate as in meiosis and mitosis, there are rarely mistakes, because the DNA replication process takes the time and trouble to “proof” the master copy and correct the errors. When this occurs in the RNA, there is much less attention given to accuracy and errors more easily slip by.
For example, DNA replication makes roughly one error per billion bits of information. With replication in the RNA there is approximately one error per ten thousand bits of information. The surviving errors have the potential to disrupt normal cell function, making it vulnerable to malignant processes (i.e., cancer) that emerge over time.
This makes the RNA somewhat “unstable” vis-à-vis the DNA and while no one can be certain, the very first viruses were thought to be RNA viruses.
Originally, and until very recently, viruses were seen as parasites that “sponged” off living cells, causing damage to the cells in the process of diverting resources. Now, scientists are viewing viruses from a completely different perspective—one that has major implications for both evolutionary biologists and everyday life.
For example, the textbook role of evolution is that mutations in DNA spread vertically (top to bottom) but are confined within a specific species. Viruses, however, allow for similar mutations to spread horizontally, which can affect multiple species. Take the human immunodeficiency virus (HIV): the oldest confirmed HIV sample appears in a blood specimen taken in Léopoldville, Belgian Congo, in 1959. The details of what happened are more involved than I can cover here, but the “short” answer is that chimpanzees and perhaps other small primates developed the monkey equivalent of HIV (designated SIV for simian immunodeficiency virus), and then one or more people became infected when a monkey with SIV bit a person. Viral driven mutations in the SIV allowed the virus to now affect humans as well as monkeys.
Additionally, it may be possible in Africa to contract viral diseases carried by bats and smaller primates from “bushmeat” if the viruses are present in the bushmeat. Bushmeat is often dried, salted, or smoked, but these preparations are not sufficient to destroy any pathogens in the meat. So, in this paragraph, and for the sake of simplicity, I’ve pushed but not transgressed the margins of reality and theory. What I’ve said is defensible, but there are caveats that a trained scientist would point out. And when you think of “bushmeat”, think of “roadkill”.
So, monkeys can carry viruses that can ultimately infect humans because of the similarities between chimps and people (98.7% semblance in terms of protein coded DNA). In other cases, an intermediate host is necessary. Take Ebola, for example. We don’t know with certainty, but Ebola might very well have formed in bats. Over time, the Ebola virus mutated and replicated within the bats who are known in virology as reservoirs. However, because bats are much less similar to people than chimps, the virus might not sicken a human in a significant way should an infected bat bite him directly. However, should the bat bite a monkey or if a monkey happens on a dead bat carrying Ebola and eats the bat, then the Ebola virus may be able to gain a foothold in the money and mutate in a way that the sick monkey can now infect a human with Ebola that way. Ebola usually does not kills bats. If it did, then it would be destroying the only opportunity it has to exist.
As far as monkeys are concerned, more than 90% of Ebola infected monkeys die, so it is important (to the virus) that the monkey pass on the virus to another monkey or human in a matter of a few short days that they monkey still has left to live.
The absurd life of bats
Bats have gotten a bad reputation in life. Because they are nocturnal creatures that often live in caves, they are poorly understood, and have a somewhat grotesque appearance, with their leathery wings and sharp teeth, and because they have become a staple of gothic
horror novels, Hollywood frightfests and are known to be carriers of rabies, many people avoid them. I remember hearing as a child growing up in the country that they often got tangled in your hair as you slept at night or that they would bite you on the neck, draining blood from your jugular vein. I also read a child’s book on Greek mythology in my youth and learned that when Pandora opened the forbidden box entrusted to her, dozens of bat-like creatures flew out to plague the people of the world. People would sometimes claim that bats attacked them at dusk as the creatures swooped and swished while pursuing insects to eat. Drive-in movies might perpetuate these myths.
The actual life of bats
There are many different subspecies of bats, and one or more of them are found on every continent of the planet except Antarctica. Bats live in attics, under bridges, in forests, in rock crevices, in mine shafts, and, of course, in caves. A colony of bats can range from several dozen bats to several million (the Bracken Cave in Texas has an estimated twenty million bats in it). The colony can roost just under the surface of the ground or as much as several hundred feet below ground. The size of a colony is determined by such variables as the convenient supply of food, suitable nesting conditions, temperature, and so on. For the sake of this post, I’ll focus more or less on Africa, but other continents, such as Asia, are not so different.
Bats live from five to thirty years. They eat everything from moths, flies, and mosquitoes to flowers and nectar, and even frogs and birds (generally depending on the subspecies). Pregnant females give birth to a single pup following a gestation period of forty days to almost five times that length, again depending on the subspecies. Bats have nurseries in many cases, where the mother can care for and protect her young from snakes, rats, raccoons, and other predatory animals.
A new virus is most likely introduced into a colony of bats by another bat. It is not unusual for bats to travel fifty miles or so in an evening, and this may bring them into contact with bats from an infected colony. They can also pick up diseases elsewhere, such as from sources of water where cholera, typhoid, the poliovirus, and hepatitis may be present. Vampire bats feed on the blood of other animals, and some bats will feed on carrion. Regardless, once a virus enters a colony, the crowded conditions can allow it to spread like wildfire to other bats in the bat community.
It is not just the press of one bat next to its neighbors that spreads the virus, nor is it simply the mutual grooming and mating. It’s the “urine rain.” Picture in your mind a row of several hundred bats hanging upside down on the ceiling of a cavern, with several other rows of bats underneath them. As the bats defecate and urinate during their sleep cycle, these body fluids shower down on the bats below. A number of strains of Ebola—which is the most deadly virus to humans after rabies—are found in bat urine, as is Marburg, the third most deadly virus. These are called viral hemorrhagic diseases (VHD).
Unlike human communities, where large numbers of people get profoundly sick and die from a virus, bat colonies never quite reach that point. There is a lower threshold of community infection achieved, and thus the virus percolates more than it boils over. This keeps the virus active for longer periods than it would be if it were in people.
And as the bats go about their daily routine, the virus they carry constantly mutates. The mutations are, more often than not, inconsequential. The viral strain that each bat carries is different from what the other bats in the colony carry, and the strain in each bat can mutate up to forty times per year.
Mutations affect the virality of the virus, its ability to spread to other hosts, and its ability to elude the host’s immune system. Generally, while the specific strain of the virus is the same among all bats carrying that strain, there is some variation from bat to bat within that strain, because the mutations in one sick bat do not typically show up in another bat.
Yet, there is an effect called parallel evolution, more precisely known as homoplasy, which occurs when the same mutation appears in two separate hosts that have not been in contact with each other. This is not a paranormal event, but rather a statistical probability given the potentially hundreds of thousands of infected bats in a colony with Ebola, the annual mutation rate, and the fact that Ebola is an RNA virus, which makes it more likely to mutate than a DNA virus.
However, this homoplasy makes it difficult for virologists to isolate a virus, as it provides the virus with multiple pathways to reach the same potential—whether in evading the immune system, increasing the transmission rate from host to host, and so on.
Ebola comes to America
In December 2013, a two-year-old Guinean boy named Emile Ouamouno became patient zero in the largest outbreak of Ebola yet. It is uncertain how Emile contracted the virus, but researchers are fairly certain it arrived in his village of Gueckedou carried by a fruit bat. What is also certain is that members of Emile’s family died of Ebola.
Thomas Eric Duncan was born and lived in Monrovia, Liberia, when, in mid-September 2014, he helped transport a pregnant woman with Ebola to a local hospital. Four days later, he went to the airport, where he denied any contact with the disease in order to board the first of several aircraft that would take him to his ultimate destination in Dallas, TX. Four days after arriving in Dallas, he showed early symptoms of the disease and went to an area hospital. Because they were unaware of his travel from another country where there was a viral hemorrhagic fever outbreak, they misdiagnosed his condition and sent him back to his motel with antibiotics, which are useless in treating a virus. His condition worsened, and he returned to the hospital, where shortly thereafter, he died of Ebola. Two nurses who cared for him also contracted the disease but survived. This incident revealed how unprepared the U.S. was if, not when, it faced dozens, if not hundreds, of Ebola patients in the event of an outbreak of its own. To say that 11,325 people in Africa died in this outbreak is to vastly undercount the true number of victims.
When Ebola came to America, we learned that flimsy masks and paper gowns were useless against a deadly disease like Ebola. Our facilities were also grossly inadequate. We discovered that we had only four hospitals in this country capable of safely caring for a patient with this deadly disease. These four hospitals had a total of eleven beds in suitable containment. Today, there are fifty-six hospitals with slightly more than 100 beds available should another outbreak occur. Even so, that is still not nearly adequate, and the cost per bed to increase its usefulness in dealing with a viral hemorrhagic disease is no doubt astronomical and so many will doubtlessly die when Ebola strikes this country again.
The past and future of viruses
The huge beast plodded slowly through the storm, impervious to the freezing temperatures and the snow around it. It was one of a small herd of half a dozen. They lumbered over and around small rises and across pressure ridges. As they reached a relatively flat plain, one hesitated as if trying to determine its bearings. These elephant-like creatures were wooly mammoths.
Then the herd resumed its trek to the west when, suddenly, without warning, the ice under one monster’s feet fractured, and the mammoth creature—a woolly mammoth, to be precise—fell through the ice into the water. In five minutes’ time, the mammoth reached the bottom of the small lake. Two minutes later, it was dead. In less than six hours, it would be well on its way to freezing solid, though that would take much longer. The absence of scavengers in this pond meant that much of the carcass would be preserved. Fifty thousand years more, it would be discovered by Russians living in Siberia who noticed one of the tusks protruding from the snow. The villagers notified the authorities, who gathered some scientists and flew to the spot where, by now, a tiny bit more of the creature was exposed. The researchers were excited. How long ago had this mammoth died? From what did it die? What would the stomach contents reveal? Would there be any surprises?
Both science fiction movies and scientific journals occasionally feature themes in which paleontologists discover preserved carcasses in a deep bog or tissue in a frozen lake or glacier, and as it warms up, it releases some deadly virus to which people have no immunity. This is reminiscent of the “Mummy’s Curse,” except that mummies don’t carry viruses but bacteria, which, in theory, can be equally deadly.
The skeletal remains of thousands of wooly mammoths have been discovered. Almost fifty were preserved in ice and still have their skin and organs intact. Most of these were discovered in Siberia. Some have so-called “zombie viruses” in their carcass.
Three years ago, a clinical lab and pathology newsletter called Dark Daily revealed that scientists revived and classified a total of thirteen ancient “zombie” viruses discovered in the Siberian permafrost. A zombie virus is a prehistoric virus that has survived in the ice or permafrost and is able to be reactivated from its dormancy.
Fortunately, and according to geneticist Jean-Michel Claverie of Aix-Marseille University:
The viruses we isolated were only able to infect amoebae and posed no risk to humans . . . However, that does not mean that other viruses – currently frozen in the permafrost – might not be able to trigger illnesses in humans. We have identified genomic traces of poxviruses and herpesviruses, which are well known human pathogens, for example.
Claverie continues, noting that drilling through the permafrost deep into the Earth’s core, in search of oil or for other purposes, might bring viruses that thrived a million years ago to the surface.”
Our immune systems may have never been in contact with some of those microbes, and that is another worry . . . The scenario of an unknown virus once infecting a Neanderthal coming back at us, although unlikely, has become a real possibility.
Researchers recall how, in 2016, a twelve-year-old boy in Siberia died along with 2,649 reindeer from Bacillus anthracis, a virus released from a carcass containing it. For almost three-quarters of the twentieth century, the carcass was sealed in ice and permafrost. However, one summer, the temperature rose to 95 degrees, allowing the virus to reappear. In total, three dozen other people were sickened with anthrax.
So, it is possible conceivable that some long lost virus might appear and decimate modern man. Whether it is probable or even likely is a different story.
Viruses are not all bad. They play several useful functions, such as providing the necessary proteins for the placenta to develop and anchor to the endometrium during pregnancy and in providing diversity within a species. If a species is too homogeneous (i.e., lacking diversity), then there is a greater extinction threat to that species from disease.
The future of viruses
Virologists speculate that there are several different “families” of viruses that present potential and future threats to civilization. These categories include influenza viruses, which could mutate into particularly deadly strains as the Spanish flu did at the end of World War I. Influenza is a highly contagious virus. Also of concern are the coronaviruses, of which COVID is one. This family killed well over one million Americans between 2020 and 2023. Finally, there are filoviruses, named after the Latin word *filum*, meaning “thread,” as these viruses appear thread-like under a microscope. Viral hemorrhagic infections such as Ebola and Marburg are examples of filoviruses. Additionally, there are orthopoxviruses such as monkeypox.
The rapid mutation rate (particularly in RNA viruses) and homoplasy pose challenges to producing vaccines. However, artificial intelligence (AI) has tremendous, yet largely untapped, potential to stay one step ahead of viruses by forecasting what mutations might occur in the coming months. While most mutations in nature are random and therefore unpredictable, certain barriers in nature define what is and is not possible or likely, making viral replication a tad more certain.
Moreover, oncologists are harnessing viruses and turning them into oncolytics, (see my link below for an understanding of how oncolytics are being engineered).
Keep in mind that this essay addresses only one part of the problem. Bacteria can take human life with equal relish. But hopefully we will have successes in the future to match and offset whatever defeats occur.
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