## Metadata - Author: [[Nathan Wolfe]] - Full Title: The Viral Storm - Category: #books ## Highlights - it is largely believed that viruses, in any given ecosystem, play the role of “trust busters”—helping to ensure that no one bacterial species becomes too dominant—thereby facilitating diversity. ([Location 339](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=339)) - How viruses choose when to launch themselves remains largely unknown, but they almost certainly monitor the environmental variables of their world when making these decisions. ([Location 359](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=359)) - While still speculation, it would not be surprising if viruses responded to environmental cues indicating severe stress or pregnancy by activating. Since severe stress can indicate the possibility of death, it may be their last opportunity to spread—a dead host is also a dead virus. A pregnancy, on the other hand, presents the opportunity for spread either through genital contact with the baby during childbirth or during the kissing that inevitably follows the birth of a baby. ([Location 362](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=362)) - From the perspective of a bug, a symptom can be an all-important means of enlisting our help in moving itself around. Microbes often make us cough or sneeze, which can permit them to spread through our exhaled breath, suffer from diarrhea, which can spread microbes through local water supplies, or cause open sores to appear on our skin, which can spread through skin-to-skin contact. ([Location 390](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=390)) - Certain viruses like HIV and the Ebola virus, which use RNA rather than DNA for their genetic information, manage to live with an average of only ten thousand base pairs of genetic information, an incredible level of biological minimalism. How they manage to replicate with such a small amount of genetic information, let alone do something remarkably complicated, like altering the behavior of their hosts, is truly amazing. Viruses manage to function with such few genes through a variety of tricks that allow them to maximize the impact of their diminutive genomes. Among the most elegant is a phenomenon called overlapping reading frames. As an analogy, take a poem of around thirteen thousand letters—say, T. S. Eliot’s poem The Waste Land. It has roughly the same number of letters as the Ebola virus has base pairs. When you read The Waste Land, it has meaning, tempo, reference—all of the characteristics we normally expect from literature. In the same way, the genome of the Ebola virus has meaning, with base pair letters making up genes that get translated into the proteins that provide the virus with its capacity to function. If you take the first stanza of The Waste Land, around a thousand letters, and begin to read it starting with the second letter instead and move the first letters of the other words, it’s a disaster. “April is the cruelest month” becomes “Prili sthec rueles tmonth.” Nonsense. Now imagine that embedded within the stanza was a second poem so that both readings, the one that starts with the first letter and the one that starts with the second letter, lead to fluent comprehensible verses. Now imagine that you took the same stanza and read it backward and that a third hidden stanza emerged from the same letters. This is precisely what viruses can do. A good challenge to poets (or perhaps computer scientists) would be to create such a stanza to see if they could be as creative as natural selection has been with viruses. ([Location 428](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=428)) - Hunting, while undoubtedly beneficial for the first of our ancestors who engaged in it, presents certain undeniable risks for acquiring new and potentially deadly microbes—risks that would continue to have an impact on their descendants for millions of years to come. ([Location 559](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=559)) - We tend to think of events like sex or childbirth as intimate, and they certainly bring together individuals in ways that normal interactions cannot. But from the perspective of a microbe, hunting and butchering represent the ultimate intimacy, a connection between one species and all of the various tissues of another, along with the particular microbes that inhabit each one of them. ([Location 640](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=640)) - mosquitoes and water provide narrow paths from one host to the next. Mosquitoes, for example, are not syringes. They are fully functional animals that have their own immune systems, and even those microbes that can manage to evade the mosquitoes’ defenses will be limited to those in the blood. Similarly, water generally passes on those microbes that live in the digestive tract. Hunting and butchering, in contrast, provide superhighways connecting a hunting species directly with the microbes in every tissue of their prey. ([Location 669](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=669)) - Two close primate relatives—chimpanzees that live and hunt diverse animal species in central Africa, and humans with rapidly expanding territory and globally interconnected relationships—would prove to be an important combination. A recipe for pandemics. ([Location 702](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=702)) - Low population densities, such as those exhibited by our ancestors, have a marked impact on the transmission of infectious agents. Infections need to spread. If population sizes are low, it is much harder for this to happen. The scientific term for substantially reduced population sizes is population bottlenecks, and when population bottlenecks occur, species should be expected to lose their microbial diversity. ([Location 768](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=768)) - Chronic agents (like HIV and hepatitis C virus), unlike acute agents, do not lead to long-lasting immunity in their hosts. They hang on to their hosts, at times holding on for a host’s entire lifetime. These agents have a better capacity than acute agents to survive in small populations. ([Location 776](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=776)) - As with the population bottlenecks that our ancestors swung through, the cooking that became their standard way of life served to again diminish their uptake of new microbes, helping limit their microbial diversity. ([Location 802](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=802)) - While we still understand very little about the ecological factors that lead to microbial diversity, there are some key factors that certainly play a role. We know, for example, that the biodiversity of animals, plants, and fungi supported by tropical rain forest systems is higher than any other ecosystem on land. When our ancestors left the rain forest, they entered into regions with diminished biodiversity. The diversity of microbes would almost certainly have been reduced, as would the diversity of the host animals that they infected. So the savanna grassland habitats likely housed fewer animals and a lower diversity of microbes capable of infecting them, which in turn contributed to lower microbial repertoires for our ancestors. ([Location 820](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=820)) - From a human perspective, the ape lineages served as a repository for the agents we’d lose—a microbial Noah’s ark of sorts, preserving the bugs that would disappear from our own bloodlines. These great ape2 repositories would collide with expanding human populations many centuries later, leading to the emergence of some of our most important human diseases. ([Location 864](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=864)) - Malaria has had such a profound impact on humanity that our own genes maintain its legacy in the form of sickle cell disease. Sickle cell, a genetic disease, exists because its carriers are protected from malaria. Protection was so important that natural selection maintained it despite the debilitating disease that appears in approximately 25 percent of the offspring of couples that each carry the gene. People who are afflicted with sickle cell have their origins almost exclusively in one of the world’s most intensely malaria affected areas—west central Africa. ([Location 871](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=871)) - The loss of microbial diversity in our early ancestors and the resulting decrease in their genetic defenses would make us susceptible to the microbial repositories that our ape cousins maintained during our own microbial cleansing. ([Location 935](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=935)) - Domestic animals continue to feed new microbes into the human species. These bugs derive not from the animals themselves, but from wild animal species that they are exposed to. Our domestic animals act as microbial bridges, permitting new agents from wild animals to make the jump into us. ([Location 1070](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1070)) - In effect, domestication provided a triple hit to our ancestors when it came to microbes. It provided sufficiently close contact with a small set of domesticated animals, allowing their microbes to cross over into us. At the same time, domestic animals provided a regular and reliable bridge to wild animals, giving their microbes increased opportunities to cross into us. Finally, and perhaps most crucially, it permitted us to have large and sedentary communities that could sustain microbes that previously would have been a flash in the pan. ([Location 1172](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1172)) - Most of the diversity in mammalian microbes resides in other animals, not humans. Some animals house greater microbial repertoires than others. For example, fruit bats are a notorious reservoir species. They often live in large colonies and are highly mobile “travelers” connecting multiple regions with high levels of biodiversity. On average a species of colonial fruit bat will have a greater diversity of microbes than, say, a two-toed sloth living a largely solitary life. ([Location 1290](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1290)) - Viruses like HIV are generally considered to be present exclusively in humans, as are bacterial microbes like tuberculosis and parasites like malaria.5 Yet it’s often difficult to make the human-exclusivity call. Unless we have comprehensive data about the diseases of wildlife, it’s hard to know if there may be a hidden reservoir of a supposedly exclusive human agent that could reenter human populations. And our understanding of the diversity of microbes in wild animals is still in its infancy. We know very little about what’s out there. ([Location 1437](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1437)) - Work done on archived specimens from South Africa shows that the fungus has infected African frogs since at least the 1930s, decades before it hit any other continent. This points to an African origin. Yet at some time, the fungus spread and did so quite effectively. How did it manage to get so cosmopolitan so quickly? One possibility is the exportation of frogs. The researchers who discovered the early evidence of chytrid in South Africa also noted that some of the species of the frogs infected were commonly used in human pregnancy tests. When injected by lab technicians with urine from pregnant women, African clawed frogs (Xenopus laevis) ovulate—which made for an early, if significantly more cumbersome, version of the common pregnancy dipsticks used today! Following the discovery of this human pregnancy test in the early 1930s, thousands of these frogs were transported internationally for this purpose. ([Location 1499](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1499)) - Over the past few hundred years, humans have constructed a radically interconnected world—a world in which frogs living in one place are shipped to locations where they’ve never previously existed, and one where humans can literally have their boots in the mud of Australia one day and in the rivers of the Amazon the next. This radically mobile world gives infectious agents like chytrid a truly global stage on which to act. We no longer live on a planet where pockets of life persist for centuries without contact with others. We now live on a microbially unified planet. For better or worse, it’s one world ([Location 1514](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1514)) - We no longer live on a planet where pockets of life persist for centuries without contact with others. We now live on a microbially unified planet. For better or worse, it’s one world. ([Location 1517](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1517)) - Although there’s no straightforward way to confirm it in the absence of specimens, Voronoff’s transplants almost certainly led to the transmission of potentially dangerous viruses into humans who received these tissues. Transplanting living tissue between very closely related animals eliminates all of the natural “barriers to entry” that microbes face, and remains one of the riskiest imaginable ways for a microbe to jump from one species to the next. ([Location 1747](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1747)) - Transplanting living tissue between very closely related animals eliminates all of the natural “barriers to entry” that microbes face, and remains one of the riskiest imaginable ways for a microbe to jump from one species to the next. ([Location 1749](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1749)) - Transfusion, transplantation, and injection, while some of the most critical tools for maintaining human health, have also contributed fundamentally to the transmission and emergence of pandemics. These technologies have connected us with one another’s blood, organs, and other tissues in ways unprecedented in the history of life on our planet. They have served to make us, among other things, the intimate species ([Location 1752](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1752)) - The consequences for connectivity are substantial. A back-of-the-envelope calculation suggests that a person living with hemophilia A in a city like San Francisco will inject themselves with up to 7,500 doses of clotting factor VIII by the time that they’re sixty. That means that this person will potentially have had contact with the blood-borne microbes of 2.5 million people during the course of their lifetime. ([Location 1792](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1792)) - In terms of sheer number of procedures, blood transfusions trump organ transplants by far. But while the number of blood transfusions will always be greater than the number of organ transplants, the movement of an organ is a substantially more dramatic biological event. Organ transplantation involves the movement of blood as well as a large amount of tissue, so any microbes present in the blood or the tissue being transplanted will move along with the organ into the recipient. ([Location 1802](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1802)) - I told you that rabies didn’t transmit from human to human. To be slightly more exact, there have been no documented cases of natural transmission of rabies from human to human. There have, however, been a dozen or so well-documented cases of rabies moving from one person to another. And every one of them has been due to a transplant with an infected organ. The majority of these cases of rabies transmission have been due to cornea transplants, perhaps because the cornea is one of the only nervous system-related tissues currently transplanted; and rabies is primarily a virus of the central nervous system. ([Location 1807](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=1807)) - we’ll find on average one or two viruses per year over the next ten years, and that’s likely a conservative estimate. ([Location 2048](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=2048)) - Whether from the pressures of the workers themselves or the roads they create, the practice of logging changes the frequency at which humans have contact with wild game. The more contact that occurs, the better the chance that a new agent will jump over. ([Location 2109](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=2109)) - Yet in an immunocompromised host, quickly evolving microbes can often gain precious time, free of immune pressure, to go through a few more generations of reproduction, increasing the probability that they will come upon the right suite of adaptations necessary to take hold in a new species. ([Location 2131](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=2131)) - The fact that people in direct contact with the blood and body fluids of wild animals also have HIV and may be immunocompromised represents a serious risk for the emergence of new microbes. Hunting and butchering provide opportunities for contact with the microbes present in virtually every animal tissue. When these agents are regularly in contact with people with limited defenses, it may provide a shortcut for microbes as they traverse the boundaries between species. ([Location 2143](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=2143)) - Historically, a single animal would feed a family or at most a village. With the advent of processed meats, a single hot dog consumed at a baseball game can consist of multiple species (pig, turkey, cattle) and contain meat derived from hundreds of animals. When you bite into that hot dog, you’re literally biting into what was only a few decades ago an entire farm. ([Location 2166](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=2166)) - We credit the eradication of smallpox to a vaccine. But it’s worth examining this further. The vaccine that allowed us this triumph was actually an unadulterated virus that we harnessed and used for our benefit. In fact, even the word vaccine itself derives from the Latin term for cowpox, or variolae vaccinae, where variolae means “pox” and vaccinae means “of cows.” In other words, at its very heart, the concept of a vaccine is the productive use of one virus to fight another. ([Location 2866](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=2866)) - Introductory courses in public health make firm distinctions between infectious and chronic diseases. They place infectious diseases like HIV, influenza, and malaria on one side of the aisle and chronic diseases like cancer, heart disease, and mental illness on the other. Yet these distinctions do not always hold up to greater scrutiny. ([Location 2889](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=2889)) - Consider the human body. Only about one out of every ten cells between your hat and shoes is human—the other nine belong to the masses of bacteria that coat our skin, live in our guts, and thrive in our mouths. When we consider the diversity of genetic information on board, only one out of every thousand bits of genetic information on and in us can properly be called human. The bacteria and viruses represented by thousands of species will outnumber the human genes every time. The sum total of bacteria, viruses, and other microbes present in our body is called the microbiota, and the sum total of their genetic information is called the microbiome. A new science has developed in the past five years to characterize the human microbiome. ([Location 3023](https://readwise.io/to_kindle?action=open&asin=B004V9O58E&location=3023))