Lancaster Physician Fall 2021 - 16

L A N CA S TERMED I CALSO C IET Y. O R G
Healthy Communities
HOW
AND
WHY
Do
COVID-19
Variants
Occur?
JOSEPH M. KONTRA, MD,
Penn Medicine Lancaster General Health
F
or the last 19 months, the world has been in the grips of a once-in-a-millennium
pandemic of a highly contagious virus, SARS-CoV-2, the cause
of COVID-19, which has resulted in over 224 million cases and caused
over 4.5 million deaths worldwide. While many aspects of the COVID-19
pandemic have challenged comprehension by both the public as well as epidemiologists,
it is the development and consequences of SARS-CoV-2 variants
that have proven most perplexing. This article will focus on the process of
variant evolution and its consequences.
The most basic question is, of course, how do variants develop? All microbes
have genetic material that must replicate in order to produce the next generation,
thus insuring the survival of that microbe. In the case of SARS-CoV-2, the
genetic code consists of RNA. Four nucleotide base pairs constitute the RNA
code. The precise sequence of nucleotides then encodes for specific amino acids,
the building blocks of proteins. This is especially important in the spike protein
of SARS-CoV-2, which is the critical attachment site for viral infection of human
cells. It is the viral key that fits into the ACE-2 receptor lock present on the surface
of human cells and which allows the entry of the virus into cells. Infection of
the cell results, and the replicative process repeats itself until or unless the virus
or the infected cell is killed.
A natural second question is why does this happen? As humans, we tend to
anthropomorphize the natural world and look for and assign motives to natural
process. But there is no intent or strategy in nature. For evolution in general,
and viral evolution specifically, the answer to why is simply mathematics. Viral
replication occurs at breakneck speeds but is an inefficient process that is prone
to errors in copying the nucleotide genetic sequence. Each new arrangement of
those building blocks is an experiment of nature. The vast majority of mutations
have either no measurable consequence or are in fact detrimental to the survival
of the next generation of virus. However, a random change in the genetic code
may also result in a change in that key spike protein that provides the virus a
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Lancaster Physician Fall 2021

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