XBB.1.16 'Arcturus' is a descendent lineage of XBB, a recombinant of two BA.2 descendent lineages of Omicron. So is XBB.1.5 'Kraken'. But they are still SARS-CoV-2, they still cause Covid-19. Newer versions of the virus tend be be more infectious - the current ones are incredibly more infectious than the original version out of Wuhan - and better at evading already acquired immunity by vaccination or previous infection. At one point, health researchers tried to figure out how many times more infectious new variants were in comparison to the first Wuhan coronavirus, but I'm not sure that anybody still does that.
As I said, SARS-CoV-2 is still very much alive, and you are mistaken when you claim that
"That virus is gone. Dead. Extinct." How do you think it still manages to kill? (Some professionals have suggested that SARS-CoV-2 should be called a cardiovascular instead of a respiratory disease because it destroys other organs than the lungs, but I assume that name change wouldn't please you.)
You don't seem to understand how exactly
"the Spanish flu petered out and morphed into a lesser deadly virus." It didn't. It
killed people, and since it kille mainly the young, who had not yet reproduced, we are the descendants of the survivors of the Spanish flu. At an early stage of the pandemic, a poster on the forum mentioned having almost been hospitalized and almost killed by the current version of the Spanish flu. This happened fairly recently, but I don't remember the poster's name, unfortunately. There are probably still people around whose ancestors may have been vulnerable to the Spanish flu but just never encountered it, so they survived and reproduced by having been isolated from the infection.
Measles also didn't just 'peter out and morph into a lesser deadly virus'.
It didn't change into a milder version. It killed, and the survivors were those who had a stronger immune response to it. How do we know that it didn't become milder in and of itself? By watching what happened when it was spread to populations, in particular in the Americas, that had never encountered it.
In the Pacific islands, to this very day, measles still kills (the unvaccinated):
Measles epidemic in Samoa and other Pacific islands (Lancet). It does so because it hasn't already weeded out those most vulnerable to it in those places. Or you could say that it 'peters out' by
weeding out, by killing. SARS-CoV-2 doesn't (or only very, very slowly), because it mainly (but not exclusively) kills people post reproduction age.
As for SARS-CoV-2:
Key Definitions
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Mutation: A mutation refers to a single change in a virus’s genome (genetic code). Mutations happen frequently, but only sometimes change the characteristics of the virus.
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Lineage: A lineage is a group of closely related viruses with a common ancestor. SARS-CoV-2 has many lineages; all cause COVID-19.
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Sublineage: A term used to define a lineage as it relates to being a direct descendent of a parent lineage. For example, BA.2.75 is a sublineage of BA.2.
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Variant: A variant is a viral genome (genetic code) that may contain one or more mutations. In some cases, a lineage or group of lineages with similar genetic changes, may be designated by the World Health Organization (WHO) or the U.S. SARS-CoV-2 Interagency Group (SIG) as a Variant of Interest (VOI), Variant of Concern (VOC), Variant of High Consequence (VOHC) or Variant Being Monitored (VBM) due to shared attributes and characteristics that may require public health action.
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Recombination: A process in which the genomes of two SARS-CoV-2 variants combine during the viral replication process to form a new variant that is different from both parent lineages. This may occur when a person is infected with two variants at the same time. The lineage that results from recombination is called a “recombinant.”
SARS-CoV-2 Variant Classifications and Definitions (CDC, Mar 20, 2023)
Viruses can change and alter their genetic make-up. When these changes occur, the virus may become more or less of a threat to the human host. Virologists are therefore interested in tracking the evolution of the viral genome.
In the case of the SARS-CoV-2 virus, it is designated a single species, but there are different kinds that can infect the patient with essentially the same disease. Biologists deploy specific terminologies to describe viruses and the use of these terms has seeped into the public discourse. Here different types of viruses have variously been referred to as mutants, variants, subspecies, and strains. This leads to
conceptual confusion. This article looks at what we mean when we refer to a viral strain.
What is a strain?
The term strain is used to distinguish a genetically distinct lineage separated from another strain by one or more mutations. A strain is a genetic variant (not to be confused with a viral variant) or subtype of microorganism (that could be a virus, but it also applies to bacteria and fungi). This is the kind of definition to which biologists abide ––it is the scientific, biological term.
It is important to realize, though, that two genetically distinct viruses are not necessarily biologically (functionally) any different from one another. Whereas a variant differs from that of the reference organism or ‘wild type’ to be designated a strain, a variant should be in possession of unique and stable phenotypic characteristics. A variant is thus called a strain when it reveals distinct physical properties. This means that all strains are variants, but not all variants are strains.
(...)
Are there strains of SARS-CoV-2 coronavirus?
In the case of SARS-CoV-2 coronavirus, the reality is that no cause has arisen in which the term ‘strain’ need be applied. If it is being used by journalists, scientists, medical practitioners, and other professionals whose linguistic choices influence the public at large then it has technically been used inaccurately.
There is only one SARS-CoV-2 coronavirus.
What is a Viral Strain? (Mar 2, 2022)
But feel free to make up your own names. It's worse when you make up your own alternative facts.
I know from earlier posts that you have decided for yourself and your child that you no longer need vaccinations or boosters against SARS-CoV-2. You
are free to make that decision, but your reason for making it is wrong.
