Many people are getting a crash course in variants as they learn more and more about COVID-19 variants.
This isn’t the first time most have heard about these types of variants though.
What to Know About Variants
Wait, other viruses can have variants?
“When humans are infected with influenza viruses that normally circulate in swine (pigs), these viruses are call variant viruses and are designated with a letter ‘v’ (e.g., an A(H3N2)v virus).”Types of Infuenza Viruses
Remember when we used to be worried about variant flu viruses?
And polio virus variants?
Global efforts to immunise children with the oral polio vaccine (OPV) have reduced wild poliovirus cases by 99.9% since 1988.”Fact Sheet: Vaccine-Derived Poliovirus
And while there have been very few cases of wild polio virus infections in 2021 (one case in Pakistan and one case in Afghanistan), we are still seeing sporadic vaccine-derived poliovirus type 2 (VDPV2) isolates, a variant of the wild polio virus, in a few more countries.
Hopefully we won’t be seeing them for much longer though, as countries have switched to bOPV that doesn’t include the type 2 polio strain. That switch was made possible by the eradication of the type 2 wild polio strain.
Do other viruses have variants?
Yes, although instead of variants, some other viruses have multiple strains, including:
- the varicella-zoster virus that causes chickenpox and shingles (multiple strains)
- the measles virus (multiple strains)
- HPV (multiple strains)
- HIV (multiple variants)
- HHV-6 (variants) – causes roseola
- CMV (variants)
- rabies virus (variants)
- norovirus (variants)
- RSV (variants)
- Ebola (variants)
- West Nile Virus (multiple strains)
- hepatitis B (variants)
And some have both…
Wait, what’s the difference between variants and strains?
“Although mutation, variant and strains can be used interchangeably when describing the SARS-CoV-2 epidemiology, it is important to understand the distinctions. Mutation refers to the actual change in the genetic sequence. Viruses whose genetic sequences differ are called variants. Variants with a few mutations belong to the same lineages. Lineages are important for showing how a virus spreads through communities or populations. Strictly speaking, a variant is a strain when it has a different characteristic.”Seven things to know about COVID-19 variants in Africa
The measles virus, for example, might have multiple strains, but they all basically act the same. Measles, and a few other viruses, like rubella, yellow fever, and polio are genetically very stable and are actually considered mostly invariant.
In contrast, a variant of a virus might be more or less contagious or more or less deadly. Or in the case of a vaccine preventable disease, a variant virus might become capable of vaccine escape, leading to vaccine failure.
“Viruses constantly change through mutation, and new variants of a virus are expected to occur over time. Sometimes new variants emerge and disappear. Other times, new variants emerge and persist. Multiple variants of the virus that causes COVID-19 have been documented in the United States and globally during this pandemic.”About Variants
The concern with the COVID-19 variants is that they will be more contagious and more deadly. Vaccine escape is also a concern. As is the possibility that some people who have already had a natural COVID-19 infection might again become susceptible to one or more of these COVID-19 variants.
“The SARS-CoV-2 B.1.1.7 variant, which is more transmissible and virulent than previously circulating strains, threatens to reverse the current downward COVID-19 trends in the United States (US) and could lead to a significant surge in cases in the next 4 to 12 weeks.”Reassessing COVID-19 Vaccine Deployment in Anticipation of a US B.1.1.7 Surge: Stay the Course or Pivot?
Viruses with variants aren’t anything new though.
“The variants of concern that have arisen to date, including B.1.1.7, B.1.351, and P.1, have done so in a human population that has largely been without any vaccine-derived protection. Variants will continue to mutate wherever ongoing transmission occurs.”Reassessing COVID-19 Vaccine Deployment in Anticipation of a US B.1.1.7 Surge: Stay the Course or Pivot?
And the best thing we can do is continuing to work to stop the spread of COVID-19 by wearing masks, practicing social distancing, and getting as many people vaccinated and protected as quickly as possible.
More About Variants
- Milestones Towards the Eradication of Polio
- Is This Year’s Flu Shot Only 9% Effective?
- Are Deadly New Rogue Strains of Mutating Measles Spreading Like Wildfire?
- Are Mutant Strains of Polio Vaccine Now Causing More Paralysis Than Wild Polio?
- Are More Polio Cases Now Being Caused by the Vaccine Than by Wild Polio Viruses?
- Why Do We Still Vaccinate If Polio Has Been Eliminated?
- What Happens if We Stop Using Oral Polio Vaccines?
- Understanding virus isolates, variants, and strains
- Reassessing COVID-19 Vaccine Deployment in Anticipation of a US B.1.1.7 Surge: Stay the Course or Pivot?
- CDC – Types of Infuenza Viruses
- CDC – How the Flu Virus Can Change: “Drift” and “Shift”
- WHO – Seven things to know about COVID-19 variants in Africa
- WHO – The effects of virus variants on COVID-19 vaccines
- CDC – Monitoring COVID Variant Proportions
- CDC – What You Need to Know About Variants
- CDC – SARS-CoV-2 Variant Classifications and Definitions
- Circulating vaccine-derived poliovirus
- Fact Sheet: Vaccine-Derived Poliovirus
- New Variant of Varicella-Zoster Virus
- Identification of Five Major and Two Minor Genotypes of Varicella-Zoster Virus Strains: a Practical Two-Amplicon Approach Used To Genotype Clinical Isolates in Australia and New Zealand
- Human Genetic Determinants of Viral Diseases
- Tracking SARS-CoV-2 Spike mutations
- CovMT: an interactive SARS-CoV-2 mutation tracker, with a focus on critical variants
- Nextstrain – Real-time tracking of pathogen evolution
- Genomic epidemiology of hCoV-19
- COVID-19 Vaccines vs Variants—Determining How Much Immunity Is Enough
- Multiple SARS-CoV-2 variants escape neutralization by vaccine-induced humoral immunity
- Naturally Occurring Single Mutations in Ebola Virus Observably Impact Infectivity
- Clinical relevance of hepatitis B virus variants