What’s a Coronavirus, anyway? 🖊

Every schoolkid learns that DNA is the code for building living beings. It is the master code, first translated into a similar structure called RNA, which then is cut to size and used as a template for every protein needed to create organic life: from the proteins which make up the structure and function of all the different tissues, to the enzymes which drive the chemical reactions necessary for life.

Viruses are best described as small genetic machines, subroutines that do nothing other than practice the fundamentals of gene copying and transmission. They consist only of a length of genetic material (called a genome: often made of RNA, but sometimes DNA), the tiny container used to house the genome as it gets spread around the environment, and a few proteins which hijack some mechanism on the surface of cells about to be infected, allowing the virus to be sucked inside. Once inside a cell, the virus’ genome uses the cell’s resources to make hundreds of thousands of copies of itself, which eventually break open the host cell, releasing the newly manufactured virus particles to infect additional host cells.

Coronaviruses are simple, spherical structures studded with tiny spike-like extrusions. Under a microscope, the spikes make the cells look like they have a halo, or corona. Enzymes found on the surface of many different types of cells, known as the ACE-2 enzymes, mistake the spikes for the chemical they are designed to react with, grabbing the virus particles as they float by, thus starting the process of swallowing them into the cell. Since mammals often have very similar ACE-2 enzymes, they are able to be infected by the same virus. Coronavirus 2019, now called COVID 19, is thought to have started as a respiratory infection in bats before it spread to other animals and then to humans.

Like many RNA viruses, Coronavirus plays fast and dirty. Its RNA genome is ready to be copied and then make proteins as soon as it enters cells, unlike DNA viruses, which must first use the cells’ own mechanisms to create RNA. DNA exists because it protects against mistakes. Lacking this protection, the mutation rate for the Coronavirus genome is extremely high, to the point that most new virus particles contain some mutation. Generation after generation, the virus becomes more mutated. These mutations, which help it cross from species to species so easily, also are its inevitable death sentence. Eventually the new virus particles will mutate to the point they lose the ability to infect their hosts. When that happens, the virus will rapidly die out, until there are far too few individuals infected with the virus to maintain an infection rate in the population. As a result, these viruses are often present for a few months, then disappear. The virus that caused SARS in 2002-2003 and the virus responsible for MERS in 2012 essentially disappeared after one season. If we can survive the initial viral onslaught of COVID-19, there is good reason to hope it will mostly disappear by late this year.

I hate to suggest intent to what is essentially a tiny organic machine, but the success of any virus is a balance between how easily it can infect its host and how lethal it is once it does so. Coronaviruses seem to be highly contagious, so they are easily spread. Since it takes several days for an individual to experience symptoms, there is time for the virus to be shed and infect more individuals. Oddly enough, the fact that COVID-19 seems to have a mortality rate of around 3 – 5% means it can spread farther than if, say, it quickly killed 30% of those who were infected. Consider Ebolavirus (another RNA virus), which is highly contagious and over 50% lethal. Infected populations can be identified and isolated fairly quickly, and, though it is a horrible death for those infected, the virus can be controlled from spreading.

Testing for a viral infection is more difficult than for a bacterial infection. Most bacteria can easily be cultured to grow and quickly reveal their identity, a process any hospital lab is equipped to perform. A Coronavirus test swab, by contrast, must be sent to a specialized lab that can create what is known as a polymerase chain reaction to the virus particles, thus revealing their presence. It is complicated lab work, reliably performed in only a few places, which results in limits on the number of individuals who can be tested in a given time.

We have very few treatments for viral infections, making them one of the most important frontiers in medicine. They are so small that there’s nothing to “kill,” so effective medications work by interfering with the infection and duplication steps described above. We have developed effective medications for managing the HIV virus, but those drugs have not been proven to control Coronaviruses (though you can be sure researchers are trying). We are left with trying to limit the spread using social means, such as our current efforts at social isolation, until hopefully the virus mutates itself out of existence.

Or we can try to develop a vaccine.

Vaccines are, of course, substances injected into the blood stream meant to stimulate the body to produce antibodies against the virus. Anyone (except the severely immunocompromised) who gets the virus will develop antibodies that will eventually, in most cases, kill off the virus inside the body. The trick to a vaccine is tricking the body into thinking the virus is already present and producing enough virus-specific antibodies to overwhelm the real virus as soon as it invades the host. Historically, vaccines were made by injecting non-functioning versions of the virus, which still generated an antibody response. With today’s technology, there is the possibility of creating a vaccine that mimics just a part of the virus, such as the spike protein. Eventually, vaccines will be made to generate antibodies to the viral genetic material itself. Although technologically more sophisticated, such vaccines can then be reliably produced by the hundreds of millions of doses.

The Coronavirus, at 120 nanometers, is big by virus standards. But compared to a red blood cell, at least 30 times larger, it is a pretty small thing. It’s proof that sometimes it isn’t the individual, but the collective, that can have a profound effect. The same is true for us, as we work together to safeguard ourselves and our neighbors, and by extension, everyone in this world.