During the 1500’s countries around the world were exposed to the Variola major and Variola minor viruses that cause the infectious disease smallpox. The history of the disease may go back to 1500BCE, and treated using a process known as variolation where the powdered form of scabs that came from existing sufferers were blown up the noses of people to be inoculated against it, but what was known as folk knowledge was not investigated until the 1780’s when another virus vaccinia or cow pox was used to ‘vaccinate’ people against the disease. The early people to use it did it not from research but from what they had inherited. An early person to use it succesfully, Benjamin Jesty, stated that he had learnt of this method as ‘folk knowledge’ as a boy. There were various versions of using peat smoke to damage the existing virus to an extent that the weakened form could be used. The use of it quite often gave a 30-90% effectiveness against the full disease.
Variola and Vaccinia are similar forms of viruses, but infection by the lesser vaccinia virus produces the correct immune response for the variola viruses.
The classification for Smallpox is:
Virus, Varidnaviria, Bamfordvirae, Nucleocytoviricota, Pokkesviricetes, Chitovirales, Poxviridae, Orthopoxvirus, Variola.
The classifications for Vaccinia is:
Virus, Varidnaviria, Bamfordvirae, Nucleocytoviricota, Pokkesviricetes, Chitovirales, Poxviridae, Orthopoxvirus, Vaccinia.
But why one virus will give immunity for another completely different species is unknown. This may not just be limited to viruses of the same genus, but may also apply to viruses that are competing over the same cells. There are concepts that are hard to pin down people who are suffering from cancer show a limited immunity to the common cold viruses as the cancer starts to expand, and that measles can rewrite immunity for other different and dissimilar viruses.
But the case of vaccinia interfering with the pattern of replication of the variola is possibly through competition over the control of the same type of cells.
This is where something that affects the epithelial cells in a particular manner may be of interest. The Chikungunya virus (CHIKV) is an unusual virus in that it promotes in the host cells fibroblasts type-1 alpha and beta interferon (IFN-α and IFN-β). This may in itself interfere with the replication of Covid-19 in the body, preventing it from spreading and accelerating into a problem.
The Chikungunya virus itself can cause problems, but the natural production of the type-1 interferon in its own process may be adapted for general use as a fire break in cases where other means have failed.
The classification for SARS is:
Virus, Riboviria, Orthornavirae, Pisuviricota, Pisoniviricetes, Nidovirales, Coronaviridae, Betacoronavirus, Sarbecovirus, SARS-CoV-1
The classification for SARS is:
Virus, Riboviria, Orthornavirae, Pisuviricota, Pisoniviricetes, Nidovirales, Coronaviridae, Betacoronavirus, Sarbecovirus, MERS-CoV
The classification for Covid-19 is:
Virus, Riboviria, Orthornavirae, Pisuviricota, Pisoniviricetes, Nidovirales, Coronaviridae, Betacoronavirus, Sarbecovirus, SARS-CoV-2
The classification for Chikungunya is:
Virus, Riboviria, Orthornavirae, Kitrinoviricota, Alsuviricetes, Martellivirales, Togaviridae, Alphavirus, Chikungunya
Which is of a completely different phylum but of the same kingdom. But because of the difficulty in defining virus history some of the classifications are loose or temporary and can change given new knowledge.