Well, it's not big news anymore. We are in the midst of a pandemic, and have been for the last 9-10 months. There is no doubting it- COVID has made a huge impact on a lot of people. It has presented the world with challenges pretty much non-stop since March, between keeping everyone inside to closing down businesses to the impending economic downturn to wild fires to riots.... yeah. I'd say there's a lot to take in right now.
A few months ago, I remember telling my friends I was going to write a post about COVID to help try to navigate some of the stress and panic. I quickly realized that as someone who WAS stressed and panicked, I was hardly in a position to get my head screwed on straight enough to sit down and write about the science and how everything really was going to be okay. I think I really didn't believe things were going to be okay, and the science wasn't helping me.
An atom-by-atom model of the coronavirus.Lorenzo Casalino, Amaro Lab, U.C. San Diego
SARS-CoV-2, or the virus that causes the disease COVID-19, is a scary little virus. Not only is it totally dissimilar from every other type of coronavirus known to infect humans (because it very likely was transmitted from a bat to a human), it's evolved to be more infectious than other coronaviruses we have faced in the past. It has evolved better mechanisms to invade our cells, and is so infectious that just standing near someone who in infected for a few minutes can mean that you catch the disease. This is because viruses are super small particles, and they depend on a host to survive. That's why wiping down surfaces is a good way to keep the virus from spreading- you're getting rid of most particles that may have landed on the surface of the object, and if you missed any, the chance that they survive without a host long enough to infect the next person to touch the object becomes smaller and smaller as time goes on.
SARS-CoV-2 doesn't look like the other coronaviruses that have historically infected humans. It resembles those found in animals, such as bats, which is how this theory of the start of transmission started. This is also one of the reasons scientists don't believe this virus was engineered in a lab and then leaked (by accident or on purpose). If someone was trying to create a virus harmful to humans, it would make the most sense to start with a virus "template" that already efficiently infects people. In addition to that, obviously in order for the virus to infect people now instead of just animals, there had to be some molecular changes that allowed that to happen. In the case of SARS-CoV-2, this change was in the spike proteins on the outer membrane of the virus. The crazy thing- according to predictive computer software, if had someone tried to engineer this virus and used a computer to predict what types of mutations to the spike protein would make the virus the most infectious, the mutation that actually happened wouldn't have been an option. In fact, the computer software predicted that a hook protein like the one on SARS-CoV-2 would actually make the virus weaker, and less infectious to our cells. Long story short- this virus probably didn't come out of a lab.
Photo credit- WikiMedia Commons
So, it's naturally occurring, it's different than the other ones, and it's good at infecting lots of people. But what makes it so deadly?
SARS-CoV-2 has a lot of tricks up it's sleeve when it comes to evading our immune systems and invading our cells. Firstly, it has a sneaky protein on it's surface called protein 16, and it makes our bodies believe that it is not a foreign cell. Our immune systems survey our bodies all the time looking for things that it can identify as invasive, and when it does, it will attack the invader. However, to make sure our immune systems don't attack our own cells, they also have the ability to detect when they interact with something that is non-foreign, or our own cells. SARS-CoV-2's protein 16 can interact with our immune system and make it believe that the virus is just another one of our bodies' cells. So right off the bat, we are at a disadvantage to the virus because our best line of defense doesn't recognize it as the enemy.
Video created my European Molecular Biology Laboratory (EMBL)
Next, using their spike protein, the virus quickly invades cells by using ACE2, a protein that sits on the surface of many different types of cells in our bodies. ACE2 acts as a little doorway that the spike protein opens, and that is how the virus gets into our cells. Most highly infectious viruses tend to use our own bodies against us like this- by using something that already exists on normal cells to invade, the virus makes sure it draws the least amount of attention to itself as possible from the immune system. By not doing anything out of the ordinary for the human body, the virus essentially makes itself invisible (again) to our immune system.
Lastly, even if the cells that get infected do manage to figure out that they are in trouble, SARS-CoV-2 can mask the signals given off by stressed cells. When cells are experiencing something problematic, they display proteins on their surface or release specific molecules into the space around them to let any surrounding immune cells know that there is a problem. SARS-CoV-2 blocks the production of these stress signals in a timely manner, so that by the time the immune system knows to act, the virus has replicated and moved on.
By the time the immune system does come into play, it's usually too late to stop the virus from moving on to other cells. However, this is the final stage of the virus's devious plan. When the immune system does finally get alerted to a problem, it starts trying viciously to get rid of something that is no longer there. This is similar to the way that we have allergies to things like dust or pollen, because our bodies believe something is wrong, so it starts trying to attack the invader in the forms of coughs and sneezes and runny noses. COVID-19 is an allergic reaction, that is more justified, on steroids. You body recognizes that something is wrong too late and starts attacking the tissue that has already been partially destroyed by the virus. Essentially, the virus pins our immune system on our own cells, while it moves on to other regions of our organs to continue it's rampage.
Ace Ventura: Pet Detective, sneaking away almost as well as SARS-CoV-2 does from immune cells.
TLDR- SARS-CoV-2 is bad to the bone. It has a lot of crazy strategies to invade our cells, spread rapidly, avoid our immune system and keep spreading across populations.
However, it is going to be okay. This has been part one, and don't worry, there is much more to come! I said at the start of this post that before I was too worried and sad to write a post, and something changed. Stay tuned for part two to hear about why, despite all the obstacles science has identified, science has succeeded in overcoming so many of them (and this is just the beginning!).
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