Coronavirus Crash Course

By Maya Arruda Email:

A computer-rendered 3D model of SARS-CoV-2

Covid-19 is a hot button issue that’s in the news 24/7 about new variants and outbreak statistics. However, not everyone knows what the coronavirus is and why it’s so deadly. 

The coronavirus pandemic is caused by a virus, but what actually is a virus? Well, a virus is a highly organized cell-like object that has a strand of DNA or RNA marinating in some cytosol inside a plasma membrane studded with proteins. A virus is extremely small, smaller than prokaryotic cells like bacteria (which are about .1 to 5 micrometers in size, depending on species, which is less than .00002 ft.). As such, it requires electron microscopy to become observable, which uses a very big device that shoots electrons through a dead sample. It has no organelles besides the cytosol. No ribosomes, no nucleus, nothing. Basically, it’s a tiny, spiky ball full of genes in clear gel and nothing else. 

Now, you may notice I used the word “object” instead of “organism,” and that is not a slip up. Viruses are not considered alive. They do not have what scientists call the seven characteristics of life. These characteristics are that living beings have cells, are highly organized, grow and develop, can reproduce, respond to the environment, maintain a constant internal state called homeostasis, and take energy from the environment (i.e. need food). Viruses can only claim 3 of these characteristics with a host; without a host, they only have 1: organization. 

Viruses use hosts mainly for reproduction. A virus is incapable of reproducing by itself, unlike bacteria which are also common causes of human illness. They don’t have the organelles required for reproduction, so they need someone who can: cells. All cells, from prokaryotic bacteria to eukaryotic humans, are viable targets for viruses, so long as the virus has the right proteins. The proteins that form the spikes on the outside are what allow the viruses to actually infect cells by exploiting cell signaling infrastructure. Long and complicated process short, all cells communicate with each other through signaling molecules and the molecules’ respective receptor proteins on the cell membrane. The spike protein allows the virus to bind to this receptor protein and infect the cell. The virus injects their genetic noodle into the host cell and commandeers all the cell’s reproductive machinery (i.e. organelles) to make more viruses. This inevitably results in the death of the host cell with new and shiny viruses about to do it all over again. 

The Covid-19 virus follows the same patterns, though its spike protein binds to receptor proteins in only human respiratory cells. It can infect both the upper respiratory tract (nose, throat, etc) and the lower respiratory tract (lungs). This results in the typical symptoms of Covid cases: runny nose, coughing, congestion, difficulty breathing, and respiratory failure in severe cases. Fever and sneezing is caused by the host immune system fighting off the virus by violently expunging trapped virus organisms and increasing heat to destroy viral proteins.

There is quite a bit of misinformation and misrepresentation of the Covid-19 virus out there. One common misunderstanding is that Covid-19 isn’t actually the name of the virus. Covid-19 actually stands for Coronavirus Disease 2019, as termed by the WHO (not to be confused with the band The Who). The real name of the coronavirus is SARS-CoV-2, and if that reminds you of a SARS outbreak back in the early 2000s, it should- these two viruses are very closely related. In fact, they are both coronaviruses. A coronavirus is, scientifically speaking, a type of virus with RNA genetic material and spike proteins, making it a very broad category. The common cold, in actuality, is caused by a coronavirus. 

The Covid-19 vaccine is made for immunization. It isn’t meant to make you incapable of getting the virus, a common misconception. Instead, the vaccine essentially trains the immune system to recognize and better combat invading viruses. This way the virus is less likely to manage to infect a cell and reproduce. However, this doesn’t mean infection is impossible for a vaccinated individual, but even in that situation, the effects of the vaccine will help the immune system know what to do to better combat the virus in case of successful infection. A vaccine is not a miracle cure that will automatically make a virus go away.  Eradication of a virus can only happen if the virus is 100% unable to successfully infect a host. A vaccine helps with this. 

However, most vaccines are equipped only to deal with one variation of a virus. This is why you’re encouraged to keep getting the flu shot every year because new variations pop up that the old shot doesn’t cover. SARS-CoV-2 is much the same. Most people who keep up with Covid-19 news should know about the latest variant that managed to drive up infection statistics. This drives the need behind the “booster” shot. The old vaccine doesn’t cover all the mutant variants. We have had many different viral variants, in the past, too, to the point where it seems like it will never end. To an extent, it won’t. 

Viral variations are created through significant mutations in the genetic code. Mutations occur during DNA (in this case, RNA) replication where nucleotides get switched out, added, deleted, or inverted. Think of the word bat and what would happen if you kept adding, changing, or getting rid of letters in that word; it would change the meaning and make it a completely different word. That’s the basic principle behind genetic mutations. Strictly speaking, everything with genetic information has genetic mutations, humans included; however, viruses have extremely fast mutation rates because of their fast rate of reproduction. These mutations can cause changes in the creation of proteins. Membrane proteins are how cells in the human body recognize each other and recognize invaders. When the viral membrane proteins change because of these mutations, it makes it difficult for the immune system to target and fight the virus. Consequently, the vaccine will lose effect as the virus mutates to be drastically different from what the immune system has been trained by the virus to recognize and combat. 

For more in depth information regarding the coronavirus, this webinar here is a good presentation on the more anatomical and physiological aspects of SARS- CoV-2 and how PCR technology can be used to identify an infection. 

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