“Tools for the Toolbox” is a series of posts that describe disease types and organ systems. Eventually I hope to include enough information that a writer might be able to do some creative mixing and matching to produce the symptoms they want to give a character. Because it’s really frustrating to throw darts in the dark and hope something lands near the bull’s-eye. Hope it helps!
I’ll start this discussion of viruses by saying that Virology is a field of study in and of itself. So there’s no way that this blog post is going to come even close to being comprehensive or even extensive. I’m doing highlights only, and I may post further information at a later date.
Viruses act in a huge variety of different ways. So instead of talking about individual viruses and what they do, let’s talk about HOW they do what they do.
Viruses don’t have much of a life. As a matter of fact, they aren’t really alive. They’re just tiny organic machines that exist to make copies of themselves. If that doesn’t get your sci-fi juices flowing by itself, check your pulse. Or your level of consciousness.
Let’s build a virus!
So. In order to make copies of a thing, you need an original. In the case of viruses, the “original” copy is a strand of genetic material. It will be DNA or RNA, but not both. Regardless, the genetic material contains instructions for making a new virus, just like human DNA contains the instructions for making a human being. This picture shows DNA and RNA, side-by-side for comparison.
So, now we have a strand of genetic material. Let’s roll it up into a ball, and stuff it into a pouch made of proteins. This pouch or coat is called a “capsid”.
The genetic material (DNA or RNA) would be contained inside. Some capsids carry structural proteins and enzymes within the coat. Pretty handy, since there’s not much room inside. (Viruses are small! Like, really small!)
And for some viruses, that’s all they bother with. They’re called naked viruses.
Settle down. (Rhinoviruses are such teases.)
Other viruses are a little more modest. In addition to their capsid/coat of proteins, they also like to give themselves an extra layer. This is known as an “envelope”, and is made of a “lipid bilayer”, which is what the cell membranes of our cells are made of. It looks like this:
You can see the genetic material, coated by the capsid, enveloped by the envelope.
So, now we have a virus.
The driving purpose of a virus… THE VERY REASON FOR ITS EXISTENCE… is to make copies of itself. But it can’t! It’s a strand of genetic fluff wrapped in one or two layers. It doesn’t carry the proper materials or machinery to make copies. Doesn’t that suck?
Um…I’m not really worried about the existential satisfaction of the common cold.
Me either, to be honest. But it does really suck. Because instead of throwing up its non-existent hands at its complete and utter lack of purpose-fulfilling-equipment, it decides to hijack someone else’s.
I have viral-purpose-fulfilling-equipment?
Yup. The cells in your body contain the equipment for replicating genetic material. And the virus wants it!
So, here’s the virus’s rather overdramatic modus operandi. It drifts around, aimless and without propulsion, until it lands by chance on a cell. Then, it injects its genetic material into the cell! It’s like hijacking a factory and replacing its blueprints with your own. (Not, I feel I should point out, that I’ve ever hijacked a factory or replaced its blueprints with my own.)
Anyway, the cell then turns into a virus-producing factory! It’s forced to use its own machinery and resources to make hundreds and hundreds of viruses! As a matter of fact, the cell-factory is pushed into overdrive by its hijackers, and eventually so many viruses are created that there’s just no room in the cell anymore. So the cell EXPLODES, spraying new, copied viruses everywhere!
And then it all begins again.
A little diabolical, no?
Aren’t there any defenses built into the cell? Viruses have been around for a long time, after all.
Well, kinda. Once infected, the cell is pretty much a goner. But that doesn’t mean it gives up. During the hijacking/infection process, the hijacked cell displays some of the viral proteins on the outside of its membrane. It’s like sending up a panic flag. This alerts the rest of the body that the cell has been infected. The flag also gives information about the infecting agent to other cells nearby so they can get their defenses up, and sends a message to the immune system that there’s an attack going on.
It’s a really nifty process, and its ingeniousness blows me away. (I love the immune system, though learning it the first time really sucked monkey balls! I blame the naming scheme. Everything and its brother was named CD28 or CD32 or whatever. Almost impossible to keep straight.)
Who gets viruses?
Different people get exposed to different viruses, though. As with any other illness (besides genetic and autoimmune diseases), the types of viruses you’re exposed to depends on your surroundings and your lifestyle. A few examples:
- Human Papillomavirus (HPV) is spread through sexual contact.
- Cruise ships, dormitories, and nursing homes are great places to catch the Norwalk virus.
- Poliovirus is more likely found in areas of poor sanitation.
- Drug abusers who inject substances into their bloodstream are at risk for Human Immunodeficiency Virus (HIV) and Hepatitis B and C.
Different people also have different ways of responding to viruses. Some people might catch it and pass it along without developing any symptoms at all, while other people may be laid up for days or even die from the infection.
For example, Respiratory Syncytial Virus (RSV) causes a slight head-cold in adults…but can cause a life-threatening bronchiolitis (infection of the bronchioles in the lungs) in infants.
What are typical symptoms?
Depends on the virus.
You got your “flu-like symptoms” for your respiratory viruses: Fever, cough, sore throat, runny nose, headache, body aches, chills, fatigue, etc.
You got your fun vomiting-and-diarrhea pattern for your gastrointestinal viruses.
You got your lymphadenopathy-plus-sore-throat-and-fever pattern for Epstein-Barr virus (mononucleosis, or just “mono”) and the initial stage of HIV infection. (lymphadenopathy = swollen lymph nodes)
There are others as well.
And then the virus can kinda do its own thing from there. HIV attacks the T cells of the immune system. Mumps also likes the T cells for an initial replication site, then heads over to other tissues like the salivary glands and the testes. Herpes viruses (which include everything from cold sores to chicken pox/shingles to painful genital rashes) like to camp out in nerve ganglia when they’re done with their initial infection. Then they flare up in the distribution of the nerves they’re hiding in whenever the fluctuations of the body’s immune system give it a chance. (ganglia = collections of nerve cell bodies)
Basically, you can model your virus on any of the above patterns, and then let it attack your character in any way you want it to. But remember that it’s more plausible to start with a few, easily explained symptoms within the same body system (neurological, gastrointestinal, respiratory, etc.) than it is to justify a total, multi-system shutdown immediately on infection. The multi-system shutdown can happen, certainly…but let it build up.
Note: Sometimes a virus’s symptoms will correlate with the method of spread. For example, the rhinovirus (common cold) is spread through the air and causes respiratory symptoms. Norwalk virus is spread through the fecal-oral route (that’s exactly what it sounds like…) and causes gastrointestinal symptoms. HIV is spread through blood and fluid contact, and it attacks white blood cells. Many viruses don’t follow these kinds of patterns, but it’s something to think about when you’re world-building.
How do you cure them?
Well, that’s a tough one. There are antiviral medications that interfere with the life cycle of a virus and minimize the damage an infection can cause, but viruses themselves aren’t really cooperative when it comes to general medical treatment.
Usually, medical personnel defer to “supportive treatment” when dealing with viruses. That is, keeping the symptoms of infection under control while the body’s immune system mounts its own defense and fights off the infection itself. If a baby has severe diarrhea and vomiting during his bout of viral gastroenteritis, he should be hospitalized so his fluids can be replaced. If a college student develops respiratory distress from an influenza infection, his breathing can be supported with a ventilator. And so on.
Antibiotics have absolutely no effect on viruses.
But Good Housekeeping told me that…
Antibiotics have absolutely no effect on viruses.
But I took penicillin once for…
ANTIBIOTICS HAVE ABSOLUTELY NO EFFECT ON VIRUSES.
Do we have any questions about antibiotics and whether or not they have any effect on viruses?
. . .
Good. Please don’t come into my office and demand I give you antibiotics for your viral infection. Please don’t come into my office and demand I give your child antibiotics for her viral infection. This happens way too often, and it really pisses me off. It’s actually one of the reasons I decided not to go into Pediatrics as a specialty, and why I hope to avoid outpatient medicine as much as possible.
Some ways to use viruses in fiction.
-Use a virus if you need an epidemic that spreads quickly, like Captain Trips in The Stand.
-Use a gentled virus as a tool for altering genetic material, like they do with gene therapy.
-Use a virus if you want to create superbacteria in a population, since a population that incorrectly takes antibiotics for viral infections will teach its bacteria how to resist any medicine it’s exposed to. Like with MRSA. Or A. Baumannii, which killed my grandfather. (Yes, this is NOT some science fictional concept, and this is NOT some fuzzy problem that we’re just passing off to our children to solve later. This is killing people RIGHT NOW. Really, really IMPORTANT people. Is your grandfather next?)
-Use a virus if you need a disease that quickly mutates. This could prevent even your genius protagonist from coming up with a cure, or could make any treatments that she cooks up completely ineffective, just in time for your exciting climax. Like with HIV or influenza.
So, viruses are pretty diabolical little buggers. Versatile diabolical little buggers. And let’s be honest: what story doesn’t need a good bit of diabolical in it? Or a good bit of versatility?
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If you use this as if it were real medical information, I will hijack your factory, and replace its blueprints with my own. Because I’m diabolical like that. And rather versatile.
Robbins and Cotran. Pathologic Basis of Disease. 7th edition. Elsevier, 2005