Fabunerds, Let’s Talk Viruses
Many friends and close family have asked me about viruses; what they are and how they work. Years ago, I took a virology course at the University of Miami medical school and it scared the living daylights out of me. However, the more we understand, the better we can critically think and respond. Read on for more information about the incredible world of viruses.
Viral Flowchart Retrieved from AmericanScientist.org
While the vast majority of us have at some point in life fallen ill to “the flu”, a.k.a. “influenza”, a virus that is part of the Orthomyxoviridae family of viruses mostly subtype A (ex. H1N1), there exist 71 families of viruses all with different mechanisms and strategies for reproduction. For example, Influenza is an RNA virus and uses its own RNA polymerase for replication.
Viruses are obligate, intracellular parasites (they are technically not alive and they are not organisms, however, they have greatly impacted how we and other organisms have evolved (read more here). They use host cell machinery such as enzymes and other proteins, in order to create new nucleic acids and envelopes, and eventually to proliferate and infect. I found a wonderful flowchart from American Scientist that shows all of the types of viruses; enveloped or non-enveloped, RNA or DNA, replicate in the cell nucleus or in the cytoplasm. The infection and reproduction strategies (obviously viruses don’t actively strategize, but for the purposes of explanation, let’s just say they do!) used by viruses are absolutely fascinating from an evolutionary viewpoint when you really consider the ability of viruses to essentially co-opt host cells for their own advantage.
Friends and family have also asked me recently about why a vaccine is not yet available for the novel coronavirus. Well, imagine first that scientists need to determine the mode of reproduction of the virus based on its genetic material (RNA or DNA).
Next, we need to know how quickly it reproduces, what its mutation rate is and how it uses the host cell to reproduce. Luckily, with advanced technologies in genome sequencing, we know the basic nucleotide sequences of many viral genomes. However, the manner in which viruses mutate and the way in which they have evolved to use our cells as hosts makes creating an effective vaccine extremely complicated. For example, Human Immunodeficiency Viruses (HIV) are retro-viruses with RNA genomes. Upon entry into the cell, their RNA is reverse transcribed into viral DNA which is then inserted into host DNA where it then benefits from the host’s transcription capabilities for replication.
To date, there is no HIV vaccine which is why prevention is so very important. Every virus is different! For example, Influenza viruses on average have a very high mutation rate, due to the virus having poor editing capabilities of its genome during reproduction, upwards of 10-4. That means for every virus that reproduces, the average number of errors per reproductive cycle is 10-4 mutations per nucleotide making it extremely difficult for vaccines to be effective if the viral strain is constantly changing. However, getting a flu vaccine does help to reduce the overall total numbers of infections even if the vaccine is not 100% effective.
Currently, scientists are tracking the spread of the new coronavirus based on sequencing techniques which can also track the number of nucleotide substitutions, or changes in sequences, around the globe. Check this article out for more information on tracking the origins of the coronavirus responsible for the COVID-19 disease.
Bottom line, viruses are super interesting and fascinating from a scientific and biological perspective, but our sordid relationship with them continues to wreak world-wide havoc. Education is key. STAY HOME, STAY SAFE!
