Abstract

Spillover discusses the concept of Zoonosis, where disease spreads from one species to another, in this book it is almost always from one type of animal to a person. Some of the diseases discussed include: Ebola, Nipah Virus, Malaria and many other dangerous and deadly diseases. Not only are the pathological disease states discussed in this book, but time is also taken to examine diseases from an ecological perspective, as well as ways to prevent the outbreaks of future zoonotic diseases.

Chapter 1: Pale Horse

Chapter Summary

The chapter begins by explaining the concept of Zoonosis, which is where an infection spreads from an animal to a human. Next the chapter discusses a case of several horses, and a human dying of a previously unknown virus in rural Australia, and the work done to identify and track the virus. After a second person died of complications with the virus, they grew concerned about how far the virus had been able to spread. they then were able to track the virus to a population of bats. The Hendra virus wasn’t the first case of zoonosis, but it served as an alarm bell to the possibility of more cases like this spreading. A good example of diseases that start as zoonosis include: HIV, Influenza, Rabies, and while not discussed in the text, the COVID-19 virus.

Important Quotes

1. “The scariest part, she told me, was the uncertainty. “It’s the fact that this disease has been around for so little that they can’t tell me whether there’s going to be any future health risk.”

   1. The reason that this quote stuck out to me is that it is something that we are currently going through with Long COVID. We have people that have been previously healthy had their entire lives upended by continual inflammatory processes from COVID-19 infections, and the disease is so new that we know very little about the possible complications.

2. “Human-caused ecological pressures and disruptions are bringing animal pathogens ever more into contact with human populations,”

   1. This quote stuck out to me because it is clear that zoonosis is a common, natural process. However, as the actions of humans continue to develop, the situation worsens and we begin to see the potential risk of pandemics of viruses like the Hendra virus.

Concept Connection

This concept will likely be connected to the rest of the book, however this is the first time that zoonotic disease was first discussed/explored, and therefore is relevant to the discussion of how diseases that are usually only seen in certain species of animals ends up spreading to others, including humans, as was seen with the Hendra Virus.

Chapter 2: Thirteen Gorillas

Chapter Summary

This chapter discusses the origins of a family of viruses that are well known to the world, Ebolavirus. It discusses five different outbreaks that are believed to have occurred as the result of a spillover, and the race to find the source. Part of the issue that they have with this is that the virus is very selective with where it attacks, and it does not remain for very long. This chapter also explores how the virus impacted the united states, mainly by infecting lab workers trying to study it.

Important Quotes

“Did you ever consider not going back to Ebola? I asked.

“No,” she said.”

This quote stuck out to me because this was after she was describing her experience in “the slammer” a special isolation unit designed for people exposed to the worst of the worst pathogens. She very well could have died from the ebolavirus, but she didn’t and she had no hesitation about going back to the work. She knew that she wanted to work with ebola, and was determined that nothing would stop her.

“Modern society has lost that sort of ancient, painfully acquired accumulation of cultural knowledge, he said. Instead we depend on the disease scientists.”

I choose this quote because it was talking about how a small village in central Africa had adopted cultural practices that prevent the spread of infections over their years of survival, a sort of cultural evolution. It was impressive to me that the ways we prevent infection are similar to the ways that they prevent infection, despite the different ways that we got there.

Concept Connection

The concept that this chapter connects to is “Survival Rate” the reason that I chose this topic is that, while Ebola is not particuarlly infectious, it is highly fatal/dangerous. On average about half of the people who contracted the disease died, at worst more than 90% of the sick people ended up dying from Ebola complications, this is practically unheard of for viruses/diseases, which is what made this virus/spillover so serious, and why so much attention was dedicated to it.

Chapter 3: Everything comes from somewhere

Chapter Summary

This chapter focuses on the mathematical aspect of disease spread. This was additionally explored by the spread of Malaria. The analysis of the mathematical data demonstrated that while the WHO tried to eliminate the spread of malaria parasites in human, they were not able to effectively accomplish this, and therefore the spread of the disease continued to explode, with efforts dampened by mismanagement.

Important Quotes

“Repeatedly passaging P. knowlesi through a series of human hosts had made Ciuca’s strain increasingly virulent, too virulent for comfort.”

This quote stuck out to me, since they are using the plasmodium parasite to essentially cook syphllis to death, but in the process they made the plasmodium too infectious, to the point where it was too dangerous to use in the future.

“And hopefully northing will happen, but of course, as she well knew, something always does happen. Its just a question of what and when”

This quote for me was a reminder that just because we are finally starting to move forward from the COVID-19 pandemic, does not mean that we have removed the scars of the past, it also means that we can relax. The population growth that we have seen increasingly promotes the spread of disease, and I fear that COVID was just the first of many pandemics that we will see.

Concept Connection

The concept connection to this chapter is Niche modeling. While they were not doing it in the traditional sense, they were able to track the spread of disease via mathematical interpretation, which allowed them to determine areas of highest risk where they could work harder for malaria prevention.

Chapter 4: Dinner at the Rat Farm

Chapter Summary

The spillover examined by this chapter is the spread of SARS around the world. The spillover was believed to have happened in a small area of Hong Kong, and by infecting many of the healthcare workers that were trying desperately to treat it, spread around the world. A key takeaway from this chapter is that the main way SARS was spreading was from patients to healthcare workers, and I think it goes to show how critical early identification and isolation is in healthcare to prevent larger outbreaks.

Important Quotes

“Conversely, if you quarentine 49 people and miss one, and that one is a superspreader, your control efforts have failed and you face an epidemic”

I think that this quote goes to demonstrate the drastic effects of super spreaders when diseases are first starting. One person that is able to cause infection in many others is catastrophic when the number of hosts is low, and that kind of momentum starts a ball rolling that is next to impossible to stop.

“Back in Singapore, health officials and government authorities cooperated to staunch further transmission. They enacted firm measures that reached far beyond the hospitals such as enforced quarantine of possible cases, jail time and fines for quarantine breakers, closure of a large public market, school closures, daily temperature checks for cab drivers and the outbreak was brought to an end.

This quote honestly made me sad. They later went on to say that there were 200 cases, with 34 fatalities, and despite the MUCH smaller population, goes to show how a strong response to an infectious agent can reduce the deaths. It frustrates me to see that we had a good example of how to manage epidemics, but we failed horrendously.

Concept Connection

The concept connection for this chapter is exponential growth. As the disease spread from person to person, each of them went on infecting more and more people, growing exponentially and eventually leading to the worldwide outbreak of SARS.

Chapter 5: The Deer, the Parrot, and the Kid Next Door

Chapter Summary

This chapter looks further in time to a bacterial spillover. The three that the chapter examines include: Q fever, Parrot Fever and Lyme Disease. All three of these zoonosis diseases are bacterial, which is not commonly found. One interesting connection that the author made is that many of the animals that served as vectors for infecting humans were found in poor conditions, which leads to an increase in disease incidence and therefore an increase in spillovers.

Important Quotes

“It will be clear, however,” Burnet wrote, “that no matter by what method a parasite passes from host to host, an increased density of the susceptible population will facilitate its spread from infected to uninfected individuals.”

I like this quote from the book because it shows that we are heading for more and more diseases to occur. The populations of species on earth continue to grow, and therefore there are more and more chances for disease to spread, and with that comes the effects that these diseases have on humans.

“We’re interlopers into this system where ticks and these hosts—the reservoir hosts—pass bacterial infections back and forth.”

This quote has some interesting implications to me, I think that it is impressive to see a situation such as lyme disease not through the eyes of a healthcare professional like I am used to, but rather through the perspective of an ecologist, so show that there is a change to the dynamics, and that we have created this problem for ourselves.

Concept Connection

A concept that this chapter connects to is predation. For a long time the way that these diseases have been looked at is that they are some kind of unthinking, foreign attacker, and all they want is to kill everything they come into contact with. That is simply not the case, these diseases. especially the bacterial ones, simply want to survive, and in order to survive, they need to consume things, unfortunately in this situation, we are the prey.

Chapter 6: Going Viral

Chapter Summary

This chapter explores the early origins of viruses, including work for the rabies vaccine, treatments of smallpox, measels and other common diseases, and the work that had to occur for us to know what we do about viruses today. It explores the life cycle of a virus, and some of the mechanisms for viral replication.

Important Quotes

“William C. Gorgas eliminated yellow fever from Cuba, by a program of mosquito eradication, without ever knowing just what infectious agent those mosquitoes carried. It was like a blindfolded hunter shooting ducks by the sound of their quacking.”

This was a good quote. I think that it speaks to just how amazing it is that even when people didn’t have the scientific advances that we do today, they are still able to achieve similar results. It also shows just how impressive Gorgas was with his work with yellow fever, something that truly required talent (and probably a bit of luck)

“herpes B didn’t make the monkey-human leap. Why not? Apparently this virus isn’t ready.”

This quote scared me. I think that it impressed upon me the fact that there is constantly a war going on between organisms, and that we are incredibly lucky to have not had as much of a problem with not only Herpes B, but the hundreds, if not thousands of viruses like it that are just waiting for the right evolutionary change to infect humans.

Concept Connection

This chapter very easily connects to parasitism. While viruses aren’t what we “traditionally” view as parasites, it is impossible to look at them as anything else. They are small microbes that enter a host, take what they need, replicate and leave.

Chapter 7: Celestial Hosts

Chapter Summary

This chapter examines the roles of bats in zoonotic diseases, with special attention given for Nipah virus. This virus is believed to spread from bats to pigs, and from there, to humans. Part of the research team sent to investigate Nipah had also worked with the Hendra source, and their experience was valuable to finding the reservoir.

Important Quotes

“But a large fraction of all the scary new viruses I’ve mentioned so far, as well as others I haven’t mentioned, come jumping at us from bats.

Hendra: from bats. Marburg: from bats. SARS-CoV: from bats. Rabies, when it jumps into people, comes usually from domestic dogs—because mad dogs get more opportunities than mad wildlife to sink their teeth into humans—but bats are among its chief reservoirs”

As previously established, finding the reservoir of a disease is critical to finding a cure/treatment for the disease, and this just goes to show that bats are one of the most common. Interestingly, at the time of the writing SARS-CoV-2 had not been discovered, but it is also partially attributed to bat populations.

“Maybe the next “Big One” will emerge from a Malaysian piggery, travel to Singapore in exported sows and then from Singapore travel the world on airplanes like SARS did”

This one made me chuckle, because once again its like the author was able to see into the future about COVID-19, and while his countries were a little bit off, the rest of it was spot on.

Concept Connection

The concept connection for this chapter is: Amensalism. The reason for this is that when the Nipah virus made the jump from bats to pigs, the bats were totally fine, but the pigs ended up getting sick, and as a result of that dying.

Chapter 8: The Chimp and the River

Chapter Summary

This chapter examines one of the most infamous retroviruses in the world: HIV. One thing that made this disease especially hard to track was the extremely long lifespan. People could go years from when they were infected to when they began to show symptoms. This meant that they could infect a large number of people, and when they started to show symptoms it was already far too late.

Important Quotes

“In the early years after its detection, the new illness was a shifting shape that carried several different names and acronyms. GRID was one, standing for Gay Related Immune deficiency. That proved too restricted, as heterosexual patients began to turn up.”

To me this was important because it showcased the large amount of information that was missing in the beginning, and how when people jumped to conclusions about the potential source, they ended up stigmatizing the disease and made it into a much larger problem.

“If the spillover of SIV info humans has happened at least 12 times, why has the AIDS pandemic happened only once? And why did it happen when it did?”

This quote is important because it demonstrates that we still dont know everything about the different types of spillovers, and that unlocking the key to this knowledge could help to limit the spread of future diseases.

Concept Connection

The concept connection for this chapter is Parasitism. The way that the HIV virus works to spread through ought the entire host is by infecting cells, and then instead of just using the cellular machinery to create more viruses, they alter the DNA of the cell by inserting their own RNA, which means that the cell can go on to make MANY more viruses, and in return wiping out the host immunity.

Chapter 9: It Depends

Chapter Summary

This final chapter is looking at a different victim than we are used to, instead of the humans being the ones that are catching the illness, it is trees. But it wasn’t a traditional illness, instead the trees were being eaten by an “outbreak of caterpillars” This chapter covers once again the importance of population density when it comes to disease outbreaks.

Important Quotes

“They are concerned, they are vaguely aware, but they don’t have the time or the interest to consider a lot of scientific detail.”

I believe that this quote goes to show part of the problem that we have with these new diseases is that most people aren’t able to understand exactly what they are dealing with, since as the author put it, they don’t have the time or the interest to go through reports, literature and all of the information that would be needed to understand these new diseases.

“Whatever happens after that will depend on science, politics, social mores, public opinion, public will and other forms of human behavior. It will depend on how we as citizens respond.”

This quote speaks to the fact that while science is key to the prevention and treatment of diseases, the ultimate responsibility comes down to us being willing to do our part, as was seen with the small villages and Ebola, even without the understanding we had, they were able to limit the spread with small, social actions.

Concept Connection

The concept connection for this chapter is Mutualism. Humans are one of the most abundant animals on the planet, and as we have seen, this makes us particularly vulnerable to disease outbreaks, however we also have the ability to work together, to solve problems and to take care of others. We have the unique advantage to consciously do things that benefit other people, and we can make sure that we limit spreads of disease, we can all benefit from each other.