A Planet of Viruses Summary and Review

by Carl Zimmer
Has A Planet of Viruses by Carl Zimmer been sitting on your reading list? Pick up the key ideas in the book with this quick summary.   An epidemic of influenza sweeps across the world every yearresulting in hundreds of millions of people sniffling and coughing. Influenza kills a relatively small number of people each year, but there are viruses around that are far worse and deadlier. Even though it killed thousands, the last Ebola outbreak could have been much worse. Viruses have the ability to spread farther and faster than ever before due to the globalization of our world.  Yet, are all viruses bad? It's true that they can do much harm to us, but perhaps they can also keep other dangers in check.  In this book summary, you’ll learn; In this summary of A Planet of Viruses by Carl Zimmer,
  • what small rodent Romans rubbed their faces with and why 
  • how viruses can save your life 
  • why it is so hard to eradicate Ebola 

A Planet of Viruses Key Idea #1: The Common Cold

While the common cold is relatively harmless, it is certainly an annoying sickness we’re all forced to tolerate now and again. Our parents, great-grandparents, and even our ancient ancestors dealt with the fever, cough and runny nose the common cold bestows.  The rhinovirus is typically what causes the common cold.  This virus was even a nuisance to the Ancient Egyptians as demonstrated by the documentation of the symptoms of “resh,” i3,500-year-old medical text Ebers Papyrus written by an Egyptian scholar.  They include a persistent cough and excess mucus in the nose. Sounds awfully familiar, doesn’t it?  The symptoms of the ancient common cold might match that of our more modern illnessbut our methods of treating it have changed considerably. Egyptians were quite sensible with a prescription of herbs, incense, and honey to apply around the nose.  The Romans, on the other hand, believed the best way to defeat the sniffles was rubbing a mouse around their nose!  Historically, there has been a range of wildly different explanations for the common cold. An imbalance of the four bodily fluids, i.e., blood, yellow bile, black bile, and phlegm was considered the cause by Ancient Greeks. Would you believe that the cause of the common cold’s eluded physicians until 1900 It was theorized by physiologist Leonard Hill that colds were caused by moving from warm to cold air, such as when taking a morning walk.  Fortunately for usthe true cause of the common cold was uncovered by scientific research through the early to mid-twentieth century. We know that the rhinovirus is responsible nowBut just because we know what it is, do we yet know how to defeat it?  The truth is, we still lack a fool-proof cure for the common cold in spite of centuries of experimenting with different remedies.  Attacking the genetic code of the virus may be the answer to a cure, but we may want to ask whether we should find a cure in the first place.  Rhinoviruses, as well as other annoying but harmless viruses, teach our immune systems to react appropriately to harmless infections.  This makes it better able to handle viruses that are more serious threats to our health.  What are these deadly viruses?   

A Planet of Viruses Key Idea #2: Influenza

Another familiar viral infection and that has been a bother to humans for centuries is influenza, also known as the flu. We know a good deal more about influenza today than in the past. And still, we struggle to find a reliable cure for this potentially deadly sickness.  Destroying the protective membrane lining a person’s airways, the influenza virus makes them more vulnerable to pathogens present in the air they breathe. This can quickly lead to fatal lung infections. During the 1918 global flu epidemic, up to 50 million people died as a result of influenza. The flu is still likely to kill between 250,000 to 500,000 people this year.  Why is influenza so dangerous? To begin with, it’s not just a single virus. There are many different types of flu viruses, constantly shifting, evolving, and swapping genes with one other. When a virus never stays the same, it’s extremely hard to create a cure for it!  Adding to its deadliness is the way that influenza spreads. Influenza viruses are carried by birds and they generally don’t spread to other species. However, the results can be disastrous when the virus does manage to cross to another speciesThree forms of bird flu virus infected pig populations during the 2009 H1N1 “Swine Flu” pandemic.  These viruses joined together to form a deadly super virus, which also joined with a pig flu virus. This made it possible for humans to contract the sickness as well.  It is frightening to realize we can’t know when a new strain will migrate from birds to humans. Still, we aren’t totally helpless against the threat of the flu. There are some simple habits, like hand washing, that significantly reduce the risk of influenza.   

A Planet of Viruses Key Idea #3: Good Viruses

Can you believe that there are viruses that are good for you? Take a closer look at the biology of bacteriophagesa particular kind of virus, if you find this hard to believe.  Bacteriophages, or “phages”, are viruses that have the power to cure diseases by eating bacteria. While studying the feces of French soldiers with dysentery in WWI, Canadian-born doctor Felix d’Herelle discovered and named bacteriophages.  d’Herelle was able to isolate the bacteria Shigella that caused the illness by filtering the stool samples. During this process, he noticed that in some places the Shigella was destroyed by an additional virus. d’Herelle tested the virus on himself and then used it as a treatment on his patients.  Despite the success of treating Shigella in this mannermany doctors were uncomfortable with the idea of injecting live viruses into patients. Phages were superseded as a treatment for diseases by antibiotics by 1940. Despite this, phages still have an important role in our modern world: as protectors of the water.  Each liter of seawater contains around 100,000,000,000 viruses. If you add up all the liters of water in the ocean that’s a whole lot of viruses! Fortunately for us, marine phages are included in this virus population. Preventing cholera and other harmful illnesses from spreading, phages destroy between 15 and 20 percent of the harmful ocean bacteria each day.  Water-borne illnesses would cause a lot more trouble without phages.  There is another form of virus that is beneficial along with phagesEndogenous retroviruses, viruses generated within the bodies of animals, including humans, actually shape our genes.  By inserting their genetic information into the DNA of the hostthe DNA of the virus is replicated when the host’s cells divide.  Discovered in 1999 by Jen-Luc Blond among others HERV-W is one important endogenous retrovirus. One of the genes of this virus produces a protein required for the cells in the outer layer of the placenta to bond called syncytin. In other words, we can thank viruses for the survival of our species as, without this retrovirus, we wouldn’t be able to carry children!   

A Planet of Viruses Key Idea #4: History of Viruses

We are constantly developing our scientific knowledge of viruses. What can the past tell us about the possible role of viruses in the future?  Take HIV as an exampleDiscovered in the 1980s, of the 60 million people who contracted the virus, nearly 30 million died as a result of the infection. HIV fuses the host’s immune cells together, then inserts its DNA into them and multiplies at an astounding rate. The host becomes susceptible to dangerous diseases such as pneumonia as the immune system is weakened, in its efforts to fight off the virus.  Scientists have devised a compelling hypothesis resulting from their research into the most infectious strain, HIV-1.  It is believed that HIV-1 was originally carried by monkeys in Cameroon.  Monkey-eating hunters in isolated villages contracted the strain firstIn the early twentieth century with the arrival of colonial settlers, the virus really began to take hold. By investigating the history of HIV and retracing the evolution of the virusscientists have been able to uncover weaknesses in the virus’s structure.  Like it or not, history tends to repeat itself.  This is why it is important to look to the past when investigating viruses. A prime example of this is Mosquito-borne viruses.  Contracted via mosquito bites, West Nile virus can cause inflammation of the brain (encephalitis) to develop, which leads to high fever, paralysis, and even deathCarried by birds from the Eastern Hemisphere to the United States, the virus was then spread in North America by mosquitoes carrying the virus from birds to humans.  Other mosquito-borne viruses are likely to repeat the pattern we saw with The West Nile case.  As the US climate becomes warmer and wettermosquitoes will continue to thrive and North American birds have shown themselves to be good carriers of the West Nile virusTo combat imported viruses more effectively in the future, researchers need to learn from mistakes made during the West Nile episode.    

A Planet of Viruses Key Idea #5: Virus Epidemics

How safe are we really? We are more effective at fighting viruses than ever before thanks to advancements in modern medicine.   Still, we just can’t predict when a virus such as Ebola will take root and that is a real problemThree hundred and eighteen sufferers died in the first outbreak of the disease in Guinea during 1976 with horrible symptoms such as violent vomiting, explosive, bloody diarrhea and even bleeding from the eyes.  Ebola has reemerged several times since then; December 2013 being the most recent outbreakEach outbreak covers more and more areaDuring the 1976 incident, the virus infected relatively few people because it traveled only between remote villages.  Today, the susceptible regions of Guinea and Liberia are more connected to the rest of the world. This means the virus has more potential to travel rapidly, and it is much harder to quarantine and more likely to infect and kill a larger number of individuals. More than 10,000 people died during the December 2013 outbreak.  Dangerous viruses such as Ebola seem to disappear from human populations between outbreaks. But the viruses continue to circulate and develop among other speciesThese viruses will change and infect humans again, but it is not possible to know ahead of time when this will happen.  Our inability to predict the behavior of naturally occurring viruses is just one factor that makes viruses a threat to our future. We are now about to synthesize viruses which means that in the future they could be used in biological warfare. Scientists are now able to rebuild relatively simple diseases such as polio after investigating their structure by sequencing DNA from scratch.  Although all vials of smallpox were ordered to be destroyed, smallpox was sampled for research purposes so it is possible that some are still intact. While smallpox is a complicated virus and is more difficult to sequence than poliothe feat is certainly achievable. The deliberate use of viruses as weapons would have devastating consequences for the future of our species and planet. 

In Review 

The key message in this book:  Viruses have always been a part of human life. They can cause suffering but some of them also keep our environment safe. We know much more about viruses today than ever before through historical and scientific research. Despite this study, we still cannot predict outbreaks.  We also can’t prevent their terrible power being used in biological warfare. With continuing investigation into the fascinating, and sometimes frightening, world of viruses we will be more prepared for the future.    Actionable advice:  Antibiotics cannot the common cold.    People often believe they should take antibiotics to treat a cold.  But antibiotics are only effective in combating bacteria and the common cold is caused by a virus, not by bacteria. Overuse of antibiotics can actually cause bacteria to evolve into more resistant strainsSo antibiotics won’t only not cure your cold: they could creatuntreatable strains of bacteria, putting you in more danger byStick to bed rest, lots of fluids and vitamin C next time your nose starts running!