In this article, I will present different Disease types and order them from external to internal. We will see that our approaches to each disease differ through these categories. Note that this is not an exhaustive list of categories.
Normally not considered a disease, I will first discuss injury. An injury is an acute disruption to one’s anatomy. Think of a papercut or a gunshot. The body was fine; then suddenly, it is not. As painful as an injury can be, they are largely treatable. A papercut will take care of itself without any intervention. A recently developed sponge filled syringe can halt bleeding from a gunshot for about four hours [1]. With an injury, there is no agent actively working to destroy you. The solution to an injury is to counteract the disruption. Even severe injuries can often be cured through surgery, given enough time to heal. (A clear exception to the previous statements are injuries to the spinal cord which often leave the victim severely incapacitated.) As there is no agent for an injury, we can say that it is completely external.
Bacteria (and parasites) are the next level of disease. They start externally and work themselves inwards. If a Bacteria is successful, it will live within the host, potentially consuming the host for its own profit. The good news, when considering treatment, is that bacteria are clearly alive! We have antibiotics that kill bacteria (and have used them for generations). A new method to address bacterial disease has been developed: tiny bits of plastic that shred bacterial cells [2]. Primarily, bacteria are completely external and they are alive; in large part, we can try to avoid interacting with it and we can try to kill it. (Though, with time, bacteria are becoming resistant to our methods; e.g. Syphilis may soon become an incurable disease [3].)
Viruses, though still external, are a different level of disease. It is largely a strand of DNA that interferes with our own cells’ mechanisms to reproduce. A virus can remain dormant within the cell for long periods of time, hidden from our immune system by our own cell membranes. It’s not alive; it doesn’t “try” to survive. It’s a biological wrench thrown into an engine. But, in this case, the wrench fools the engine to make more wrenches. It reproduces until the cell is bursting with copies of the virus; then the cell bursts sending the virus throughout the body (and the blood stream). Largely, we are terribly ineffective at addressing viruses. Our approach is to encourage the viruses to end dormancy and distribute anti-viral chemicals through the body. We can try to create vaccines to help our immune system fight off a viral infection before it takes over our body (e.g. this has been done with Human Papilloma) and we can try to avoid acquiring the virus (e.g. wearing a condom during sex, washing our hands after we shake someone’s hand). If acquired, we can encourage the virus to exit dormancy and address it with anti-viral medications.
Traversing our hierarchy, we arrive at cancer. Cancer is our first internal disease; it’s a mutation (a modification) of our own DNA. To address it, we need to find a mechanism that selects something that is only slightly different from our own cells. Or, we need to find a way to eradicate the cancer cells entirely. If a cancer is benign, then it is still localized in the body and can often be removed surgically (e.g. benign breast cancer). If it is in the Bone Marrow, the entire bone marrow can be destroyed (with radiation) and replaced from a donor’s bone marrow or from marrow grown from our own non-cancerous stem cells [4]. Or we can try to extinguish the cancer with radiation and chemotherapy.
We arrive next at genetic diseases. These nefarious diseases are our own cells working as their DNA dictates they should. It’s completely internal, and it’s a defect in our DNA. Huntington’s, Muscular Dystrophy, Sickle Cell Anemia, and autoimmune disorders are examples of this type of disease (Cerebral Palsy and Multiple Sclerosis may also be). Our treatments for these diseases are largely experimental. With Sickle Cell Anemia, a bone marrow transplant may be able to cure the patient (though this is a new and experimental approach) [5]. With the other diseases, an experimental approach is to extract our own cells, alter the DNA of the cell to eliminate the defect (perhaps using CRISPR [5]), and then introduce the cell back into the body with the hope that the new cells will replace the old defected ones. As far as I know, we have yet to be successful at replacing significant portions of our own cells with the corrected cells.
Finally, we have diseases of the mind. These are diseases that are not the consequence of issues with individual cells, but rather, they seem to be diseases of how the neural structure of the brain developed. These diseases include schizophrenia, anxiety (including obsessive compulsive disorder), and depression disorders. Again, they are completely internal and not alive. Our approach to these diseases is to try to alter the structure of the brain’s neural network through learning (accomplished with psychological therapy) and to alter the concentrations of chemicals in the brain.
[1] https://www.sciencealert.com/this-sponge-filled-syringe-can-plug-a-gunshot-wound-in-20-seconds
[2] https://www.scientificamerican.com/article/self-sterilizing-plastics/
[2] http://aac.asm.org/content/54/2/583.full
[3] https://www.nature.com/news/lab-grown-blood-stem-cells-produced-at-last-1.22000
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4581443/
[5] https://www.broadinstitute.org/what-broad/areas-focus/project-spotlight/questions-and-answers-about-crispr
