I hope everything I'm going to say is still accurate. I did go to medical school 20+ years ago. So I'm just going to go off my knowledge that I remember learning in medical school. I'm too sick and lazy to do research. Although I might try to put some images on here for you. So you can visualize what some viruses look like.
So here is what I know about viruses.
Viruses are much smaller than human cells or even bacterial cells. In fact, viruses cannot be seen with a regular light microscope. They can only be seen using an electron microscope. That's how tiny they are.
Viruses are not considered to be living things. This is because they do not metabolize, respirate, or feed. Although this topic could probably be debatable because they do contain genetic material.
Viruses are composed of genetic material (DNA or RNA) encapsulated in a protein shell. That's it. The protein shell varies in size and shape. This protein shell also contain surface antigens which is how your body's immune system recognizes the virus as a foreign entity.
Viruses are completely parasitic. They cannot survive outside of the host for very long. I don't know the exact numbers, and they vary depending on the virus, but most survive or remain viable from hours to days on hard surfaces. They don't do well on soft or pourous surfaces like clothing and blankets. Or even things like cardboard and paper which are porous. Although I think you can still pick up viruses from those surfaces for a short time.
The sole purpose of a virus' existence is to replicate itself. That's it. Replicate and spread. But a virus is not capable of replicating on its own.
In order for a virus to replicate itself it must have a host. Once a virus is transmitted to a host, it attaches to a cell membrane where the virus injects its genetic material. Once the viral DNA or RNA is inside the host cell, the virus commandeers the host cell machinery which begins replicating the viral DNA or RNA. Then, if I remember correctly, the viral RNA/DNA will code for the protein shell and the host cell will manufacture the new viruses. Once a cell is full of newly made viruses, the viral enzymes will weaken the host cell membrane causing lysis. (The cell bursts open). This releases all of the newly made viruses into the body to infect new cells and repeats the process over. This is what causes illness. The cell damage along with the body's immune response is what makes you feel sick.
Once a host is infected with enough viral load, the virus is spread to new hosts. Different viruses spread in different manners. For instance rhinovirus (common cold), influenza, coronavirus etc. are spread through respiration. Coughing, sneezing, and even breathing. The virus particles are contained in the droplets of water or bodily fluids which are expelled from one host to another. If those droplets land on a table or door handle and you touch it while there are still viable viruses on the surface, then you touch your face -- you are now infected.
This doesn't mean that you will necessarily become ill. Some people are naturally resistant to certain infections, or possibly immune. Or maybe their immune system just works faster by recognizing and killing or inactivating viruses. If you have been vaccinated or have already had that specific virus, your immune system already has made antibodies that are circulating in the blood that will attack the virus (by attaching to surface antigens on the protein capsule) and get rid of it before it makes you ill.
Some other viruses such as HIV, Human papilloma virus (HPV) Hepatitis B, and herpes simplex virus (HSV) can only be transmitted through sexual contact or blood to blood contact such as needle sticks with contaminated needles.
Some viruses are transmitted through vectors like mosquitoes or mice. Mosquitoes transmit West Nile virus and yellow fever virus etc. Mice can transmit hantavirus. Dogs, bats, raccoons etc. can transmit the rabies virus if they are infected.
It is not in the best interest of the virus to kill the host. Viruses need live hosts to continue replicating themselves. But sometimes -- especially when viruses jump species -- they can become deadly to the new host species. As I recall, most deadly viruses jump from animal to human infection. Viruses that start in animals -- like bird flu or swine flu -- are generally not as virulent and often times are not symptomatic to the animal. But when the virus jumps to humans -- it becomes much more virulent.
Did you know that some viruses also cause cancer? They are called oncoviruses. Examples include: Epstein-Barr virus, human papilloma virus (which causes cervical cancer), and hepatitis B and C.
I'll bet you didn't know that viruses can also infect bacteria. They are called bacteriophages. Or sometimes just a phage. Usually it's a small circular piece of DNA that is actually incorporated into the bacterium's DNA.
Viruses can also infect plants. The example I remember from medical school is the tobacco mosaic virus. Which infects the tobacco plant.
Viruses are not killed by antibiotics. Antibiotics will only kill bacteria. So if you have a cold, flu, or any viral infection -- antibiotics will do nothing to help you. The best way to prevent viral infections is through vaccination. That's really the only way to prevent viral infections. There are drugs that can stop or slow down a virus, once you're infected, but will not prevent it. For example, zinc is known to interfere with viral replication. Therefore if you coat your throat with zinc -- via slowly sucking on a lozenge -- at the very first signs of respiratory infection (cold or flu) you can stop or slow down the viral replication long enough for your immune system to inactivate the virus before it causes illness. Once the viral load is too high though, the zinc is ineffective.
Anti-vaxxers are ignorant and a danger to themselves, their children, and society. Vaccinations are one of the marvels and blessings of modern medicine. Vaccinations save many lives and prevent illness and disease.
RNA viruses tend to be the most pathogenic to humans because of their ability to mutate. This is why there is a new flu shot every year. Because the influenza virus mutates rapidly. Same thing with rhinoviruses. That's why you can keep getting colds over and over. It's a different mutation of the rhinovirus which you are not immune to. I believe there are over 200 known rhinoviruses.
Coronaviruses are another example of RNA viruses that mutate. Of course, COVID-19 is the newest coronavirus wreaking havoc, causing our current pandemic. Did you know that the more virulent SARS and MERS are also caused by different mutations of the coronavirus?
Some images of viruses:
Measles virus
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| This illustration provided a 3D graphic representation of a spherical-shaped, measles virus particle, that was studded with glycoprotein tubercles. Those tubercular studs colorized maroon, are known as H-proteins (hemagglutinin), while those colorized gray, represented what are referred to as F-proteins (fusion). The F-protein is responsible for fusion of the virus and host cell membranes, viral penetration, and hemolysis. The H-protein is responsible for the binding of virions to cells. Both types of proteinaceous studs are embedded in the particle envelope’s lipid bilayer. |
MERS viral particles on host cell
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| Produced by the National Institute of Allergy and Infectious Diseases (NIAID), this highly magnified, digitally colorized scanning electron microscopic (SEM) image, revealed ultrastructural details at the site of interaction of numerous yellow colored, Middle East respiratory syndrome coronavirus (MERS-CoV) viral particles, located on the surface of a Vero E6 cell, which had been colorized blue. |
Ebola virus
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| This is an electron microscopic image of the 1976 isolate of Ebola virus. The internal structures of the filamentous particle are visible, including the nucleocapsid and other structural viral proteins, and the outer viral envelope is covered with surface projections. The characteristic “6-shape” of the virus is evident. |
Influenza A virus
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| This digitally-colorized, negative-stained transmission electron microscopic (TEM) image depicted a number of Influenza A virions. |
I hope you enjoyed your virology lesson today. Isn't my brain full of lots of useful information? I am happy to impart some of my wisdom and knowledge to you. You're welcome. I could probably charge tuition to share my wealth of knowledge. :-)
I didn't even get to epidemiology yet. Perhaps another day.
That's my two cents.
Wow! I learned a lot! Don't be telling people about zinc! Giving our secret away. HA HA! J/K.
ReplyDeleteThanks for the lesson!
I know! I almost didn't include that part. :-)
ReplyDelete