Vova Prylepa. 05/22/2022
Viruses, half-dead half-living molecular parasites, have terrorized humans for over millennia. Let’s delve deep into the biology of our biological foe, the main causes of the danger it represents, and how to fight it.
Viruses are much smaller than cells and are simple containers of genetic material. They invade the cells in our bodies to procreate and mess up the processes responsible for the healthily functioning of the cell. The cells in question are destroyed in the process. They can’t create copies of themselves without being inside of a cell. In fact, on their own, they aren’t able to engage in processes we associate with life, which qualifies them as zombies. However, they do contain the necessary instructions without being able to translate them into useful biochemical components, a function for which they rely on their host cells. Once produced, these components become part of the virion (the virus particle) that will carry these instructions from cell to cell. Interestingly enough, most viruses contain only a few genes, the minimum being two to three.
Viruses mutate and evolve in order to survive better against the organisms’ attempts to suppress it (for instance, antibiotics that work on bacteria do not work on viruses). As the viral genome is being read to create new copies, the wrong base, and thus the wrong nucleotide is occasionally inserted in the gene, similar to a typo on a computer. Even though such typos happen seldom on an individual gene, because of the frequency of the replication of the virus, they accumulate with time and aid the virus with completely new dangerous properties.
For instance, HIV becomes very genetically diverse during infection because it can make the cells read and create copies of itself several times a day in an individual for years. It means that these typos build up and add mutations to the virus, allowing damage to a wider range of bodily functions than previously available, and making it harder to kill due to the number of copies. That’s why HIV is resistant to specific drugs; the genome of the virus differs with every hour from the one that was replicated before. Therefore, treating HIV with a single drug won’t affect the virus because its genes mutate very quickly and the drug won’t be adapted to stop the cells from replicating a specific HIV gene with a particular number of typos.
Why do only some of the millions of viruses cause illness?
Over long periods of evolution, a virus can either die out, kill its host (sometimes an entire species), or it can co-evolve so it can no longer cause the damage to kill the host, but can still replicate inside of it. It’ll cause a mild sickness, but the host will recover so the virus can survive.
But when the virus finds itself in a new species, it might be very dangerous for that host because the host hasn’t adapted to the disease to be able to negate its dangerous effects. That’s why a virus that doesn’t do much to animals can harm humans (such as HIV or COVID-19) and a virus that does not do much to humans can harm animals.
Some viruses are dormant in our bodies. They live within us but don’t cause any harm because they are suppressed by our immune system. They can be awoken if the immune system is damaged though, and some of them can cause serious harm, such as CMV. A person with HIV has a very weak immune system, which means it can’t suppress CMV anymore and the cytomegalovirus can destroy the retina, completely blinding its host.
Are there harmless viruses that just live in us?
Some viruses are stable outside of cells, like the coronavirus (which can be transmitted through droplets of saliva) or polio (transmitted through contaminated water), while others, like HIV, have low environmental stability and can only be transmitted through sex or blood transfusion.
Methods of prevention/ treatment
We can prevent viruses with vaccines and treat them with antiviral drugs. A vaccine is usually a component of the virus or a weakened version of the virus in some cases. It induces a response from the body to make antibodies. It is done so when the organism is confronted to an actual virus again, this time in its full strength, the antibodies will remember how to kill it off before it has a chance to cause disease. The vaccine is thus similar to a practice exercise for the antibodies.
An antiviral is a small molecule component of viral RNA or DNA. It is then modified to have the ability to disrupt the replication of the virus in question. Although the virus will not leave the body, antivirals can help treat viral infections such as influenza or Ebola.
Viruses can be fragile or strong, varying in lethality per virus based on the species. Copying errors during DNA transfer can give viruses the potential to cause more harm since their genetic makeup may change before a vaccine with a weakened version of the virus is made. Some well-known and dangerous viruses include HIV, polio, the common cold, and COVID-19, and while these can be very harmful, anti-viral treatment or vaccination can serve as a remedy against its effects.
Cover Photo: (NHLBI)