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Frank A. Bures: Viral definitions of mutation, variant, strain

Frank A. Bures: Viral definitions of mutation, variant, strain

From the COLLECTION: Recent Healthful Hints columns by Dr. Bures series
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If you have been reading or hearing about the various variants, mutations, and strains of our non-friend the (no longer) novel coronavirus, you may have really strained to make sense of the terminology. Following is an attempt to de-obfuscate the usages.

All viruses are genetic material as a code of nucleic acids in a specific order. These are called genomes (JEE-nomes). They are covered or enveloped by a protein coat that is magically attached during replication in an unwilling host’s cells, which the viruses have infected or invaded.

After the host cell ruptures, the new viruses seek out new host cells’ genetic machinery to use for parasitic continued multiplication and survival. Our current nemesis, the Sars-CoV-2 (SC2) virus is our poster child for mutations, variants, and perhaps future new strains.

Its genome consists of ribonucleic acids, RNA. Human genomes are deoxyribonucleic acids or DNA. The SC2 genome was genetically decoded and published in a scientific journal from Wuhan, China, for all scientists worldwide to share in January 2020 (the year that wasn’t?). It has around 30,000 nucleic acids in a particular order, represented by single letters.

Many viruses during the host cell hijacking and replication create a few typos in the code, which are mutations. Influenza viruses are notorious for mutating, much more than coronaviruses. Hence, there is need for new annual vaccines for “the flu.”

These errors result in viral duplicates similar to but not exactly like the parent viruses. The mutations may amount to nothing for host or virus. The slightly to largely different progeny are called variants.

The variant forms can function somewhat differently. A variant may have mutated so it is less effective at infecting cells or reproducing, which will lead to its dying out.

As in the case SC2, it could become more effective at attaching to and infecting host cells, such as the United Kingdom, UK variant B.1.1.7, which has 22 coding mutations in the viral genome, especially for the infamous spike protein.

This allows better attachment to human cell receptors called angiotensin converting enzyme 2, ACE2, which are on many of our cell’s surfaces. This variant facilitates easier spread, but not necessarily more vicious disease symptoms. The ones we have already are bad enough. The so-called South African and Brazilian variants contain different mutations from the UK one.

Some mutations allow omission of certain protein portions toward which a vaccine has been built, as in the spike protein. This makes the vaccine less effective. That may be the case with the South African variant.

Some mutations make the new variant more vicious or virulent. Fortunately, so far that has not been the case with SC2 variants.

A new or different strain is designated when enough mutations have occurred to create a variant that exhibits different viral behaviors and “looks” different to virologists, like having blond instead of brown hair.

Don’t ask me to explain further. You’ll be sorry. To date SC2 is still one strain with multiple variants, and more to come. Therefore, all Pekinese are dogs, but all dogs aren’t Pekinese. All strains are variants, but all variants aren’t strains. We’re getting there.

What has put “strain” on our understanding of the terms is the casual interchangeable use of variant and strain in many news publications. But then, common incorrect parlance has established fairly common use of the mispronunciation prevenTAtive for preventive. Strain for variant “ain’t” correct, but not as flagrantly incorrect as preventative. Had enough biological grammar for now?

The practicality of the nuances among mutation, variant, and strain is to help understand the actual medical significance of the viral mutations, which are part of the evolutionary processes of both viruses and our adaptations to them.

When you read that the UK variant has been found in 70 other countries, it doesn’t mean that people with it have ventured to those places to spread it, although that can be part of it. There is a nebulous biological concept called evolutionary pressure, which drives natural selection, for certain forms to emerge. But that’s for another time, eh?

For now, your brain been under a lot of strain reading this, so it’s time relieve the pressure and mutate out of here. At least so far, I haven’t seen any report of Teenage Mutant Ninja Coronaviruses emerging, have you?

Governors and lieutenant governors from Illinois, Wisconsin, Indiana, Michigan, Kentucky, Minnesota and Ohio are encouraging residents to make a plan for how they can get the coronavirus vaccine once they become eligible.

Dr. Bures, a semi-retired dermatologist, since 1978 has worked Winona, La Crosse, Viroqua, and Red Wing. He also plays clarinet in the Winona Municipal Band and a couple dixieland groups. And he does enjoys a good pun.


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