Sunday, June 23, 2019

Disease Post: Smallpox

Greetings and welcome to my first (hopefully of many) science posts.

If you read my last post, I was inspired by the second half of the vaccine episode of the podcast This Podcast Will Kill You (which is an awesome podcast and everyone should listen to it). In the second part of the vaccine episodes, they discussed that people not believing science and scientific research is because scientists don't make information accessible and easy to understand. I agree and think this is a huge shortcoming in the field of science. To that end, I would like to contribute to the scientific knowledge that is available out there.

Let me start with a little introduction and background:

I have my Bachelor's degree in Biology with a minor in Chemistry. I did a decent amount of focus on molecular biology at this time. I have my Master's in Microbiology and infectious diseases are certainly my passion. Currently I am taking steps (slow baby steps, but steps) towards medical school and on to be a doctor who specializes in infectious diseases (fingers crossed). Because that would be the most amazing thing ever. I have a pretty good science background. I have worked in a lab for several years and have background as a tutor. I am hoping that these things will enable me to take on this blog project.

However, my background is almost entirely in Biology and Microbiology. I can get by Chemistry alright, but that is about the extent of what I know. So as much as I wish I could educate on topics like global warming, I can't and don't plan to try unless I get help from someone who knows the field. So that means that I will end up focusing on diseases (at least to start). I do have an older post about vaccination here: Why You Should Vaccinate, and I may do more like that in the future. Right now this is a bit of a pet project and we will see how it goes.

And now for:
Disease Post One: Smallpox!

A tiny bit of background information: what is a virus? The Merriam-Webster dictionary says a virus is
     any of a large group of submicroscopic infective 
     agents that are usually regarded as nonliving 
     extremely complex molecules, that typically 
     contain a protein coat surrounding an RNA or DNA 
     core of genetic material but no semipermeable 
     membrane, that are capable of growth and 
     multiplication only in living cells, and that 
     causes very important diseases in humans, 
     animals, and plants

Basically, this means that there are several different kinds and families and types of viruses. They might have DNA or RNA genetic material which may be single- or double-stranded (which will affect how they use the host cell to make more copies). Some have an envelope around them that is basically the same as our cell's membranes. Some do not have a membrane. These will affect how a virus enters and exits a host cell and provide some level of protection/preservation when the virus is not inside a host. It is up for debate whether viruses are actually alive or not. That's not something we are going to get into here. Viruses are mostly considered non-living because of one important feature: they need another living cell in order to multiply their numbers and spread. 

Viruses are the source of many different diseases, some are lethal and others are minor. Some can even cause cancer. I'm going to underline this next point: viruses cannot be treated with antibiotics! Antibiotics treat bacterial infections, not viral. There are anti-viral medications out there for serious infections, but viruses can be harder to treat because they like to hide in our cells.

Smallpox is a disease caused by a virus, namely Variola major. (There is a less common and less lethal virus that causes smallpox called Variola minor.) The variola viruses are double-stranded DNA viruses so their genetic material is like ours! They are very large viruses because they have to carry a bunch of machinery around due to the fact that they replicate their DNA in the cytoplasm of human cells. Since we, as humans, replicate out DNA in the nucleus of our cells, the virus can't hijack our own machinery to aid them. Therefore, they carry their tools with them!

Smallpox was common around the world for thousands of years. It was officially eradicated in 1980. Smallpox virus only has one host: humans. Which made it a good target for eradication because it cannot be hiding somewhere in the environment or in an animal host, waiting to re-establish itself in the human population. Once the vaccination programs spread, the virus had no where to go, and now its gone! The only smallpox left in the world are in a couple of laboratories (both in the US and in Russia because it is a great pick for bioterrorism and biowarfare--maybe an idea for a future post as I actually took a course on that very thing during my Master's).

While smallpox seems less relevant today, it is a historically important disease that killed loads of people. According to the CDC (Center for Disease Control): "On average, 3 out of every 10 people who got it died. Those who survived were usually left with scars." It is also where vaccines started. I won't get too into all of the history here, but in the late 1700's Edward Jenner used a live vaccinia virus (which causes cowpox, a virus/disease related to smallpox) to inoculate or infect a patient. The reason for this was that he noticed that milkmaids often didn't get smallpox if they had contracted the much milder cowpox. His methods worked (luckily since he used human subjects in the days before scientific ethics was a thing). And the word "vaccine" comes from "vacca," which is latin for "cow!"

Edward Jenner vaccinating a child. Image from Wellcome Collection.

How is it spread? 

Smallpox initially infects the respiratory system and so it is usually transmitted in the air from one person to another. It can also be spread through touch because the scabs and sores contain live virus, but that is less common. Namely, it happened when the infected person sneezed or coughed virus into the air.

Once smallpox is in the body, it incubates (develops, multiplies) for several days, the CDC estimates between 7 and 19 days. During this time, there may not be any symptoms present and the person probably won't know he or she is sick.

  • First symptoms are pretty common for diseases: fever and body aches. Some patients may experience vomiting. The CDC states that this stage is not usually contagious, but it can be.
  • Next the patient will start to develop a rash in the mouth and tongue. This is when patients are most contagious! That is part of why this disease is dangerous and easy to spread: people around you don't know you have smallpox!
  • Following this stage, the sores in the mouth will begin to fade to be replaced by the signature skin sores. 
  • The sores become pustules (bumps filled with fluid) form that have a characteristic dent in the middle. 
  • The pustules will start to scab over and the scabs eventually fall off. This happens after about 3 weeks of obvious disease (from the mouth sores). And remember, the pustules and scabs are also contagious. Once the scabs are all gone, the person is not contagious anymore.
This highlights another reason this disease is important: if you got smallpox (and almost everyone did before vaccines), you were sick and contagious for about a month. If you survived. Remember the mortality rate was about 33%. Meaning that about a third of the people who were infected would die of the disease.

If the virus moved to the eye, the patient could become blind.

According to the WHO, "Between 65–80% of survivors are marked with deep pitted scars (pockmarks), most prominent on the face."

One upside: if you survived, you had life-long immunity! This means you cannot get smallpox twice!
Smallpox rash and pustules. Image from Wellcome Collection.

Prevention and Treatment:
These are not super important now that smallpox is eradicated, but there are still stocks of smallpox vaccine out there. Military personnel are the most common people vaccinated these days, and not even all of them receive the vaccine. I believe it is available to medical professionals in some places, but many never receive it. The main reason for this is that the vaccine is still a live virus (a weaker vaccinia virus that was developed in labs for the vaccine for many generations) and can cause people nearby to become infected by the vaccine strain. When a person gets the vaccine, they are supposed to avoid human contact for a while until the vaccine site heals. (I know the old vaccines gave a pox mark/pock mark and pustule, so you would have to wait for the scab to fall off, just like with smallpox. I'm unsure if the current vaccines are the same, but I know they are still contagious.)

As for treatment, there are a couple options, just in case! None of these antivirals (medication used to treat viruses) have been used to treat smallpox because there are no more cases, but they are: tecovirimat (TPOXX), cidofovir and brincidofovir.

That's about it for smallpox! I hope you liked it and learned something. And if I missed anything or got anything wrong, please, please let me know so that I can correct it! Feel free to reach out with questions or if something needs clarification. Thanks!

Centers for Disease Control and Prevention
World Health Organization
Medical Microbiology, 6th edition by Patrick R. Murray, Ken S. Rosenthal, and Michael A. Pfaller
Mayo Clinic

Also, thanks so much to my friend, Veronica, for helping me edit this post!

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