Question

Besides evolutionary processes, is there any other known reason why a virus must target human cells to grow and multiply?

Answer 1

The species Severe acute respiratory syndrome-related coronavirus: classifying 2019-nCoV and naming it SARS-CoV-2 - Nature Microbiology

The present outbreak of a coronavirus-associated acute respiratory disease called coronavirus disease 19 (COVID-19) is the third documented spillover of an animal coronavirus to humans in only two decades that has resulted in a major epidemic. The Coronaviridae Study Group (CSG) of the International Committee on Taxonomy of Viruses, which is responsible for developing the classification of viruses and taxon nomenclature of the family Coronaviridae, has assessed the placement of the human pathogen, tentatively named 2019-nCoV, within the Coronaviridae. Based on phylogeny, taxonomy and established practice, the CSG recognizes this virus as forming a sister clade to the prototype human and bat severe acute respiratory syndrome coronaviruses (SARS-CoVs) of the species Severe acute respiratory syndrome-related coronavirus, and designates it as SARS-CoV-2. In order to facilitate communication, the CSG proposes to use the following naming convention for individual isolates: SARS-CoV-2/host/location/isolate/date. While the full spectrum of clinical manifestations associated with SARS-CoV-2 infections in humans remains to be determined, the independent zoonotic transmission of SARS-CoV and SARS-CoV-2 highlights the need for studying viruses at the species level to complement research focused on individual pathogenic viruses of immediate significance. This will improve our understanding of virus–host interactions in an ever-changing environment and enhance our preparedness for future outbroutbreak.

Note also that viruses infect almost every living thing, all the way from bacteria to whales. Not just humans. Tobacco even has a virus, the Tobacco Mosaic Virus, and it also infects tomatoes, potatoes, some members of the Arum family, and is so virulent that greenhouse keepers are reluctant to even let a smoker go in, as the particles are fire proof! Roses also have viruses, as do

 

Viruses are tiny shreds of DNA or RNA (like with HIV and Covid) packed inside a protein coat, sort of like pills inside a bottle. There is an old saying in Biology, “all living things are made up of cells”, and in this definition, viruses are not living - they have to have living cells to reproduce.

 

Think of viruses as tiny tanks (the protein coat) with tiny little robot drivers (the virus) which will break into the walls of an automobile factory (the cell), shoot all the management (cell nucleus and cell DNA), take over the factory, and force it to make little tanks and robot drivers from available material, draining the cell while they are at it, and then break down the factory walls, releasing the tiny tanks, and destroying the factory (cell) in the process. They also mutate like crazy when in the infective stage, so can change, like the Delta Variant and the Omicron Variant.

see below