Every virus is a parasite that cannot exist on its own and is fully dependent on its carrier. This is the basic condition of its existence. The parasite must have its host, and thus is a living cell. Based on our long-term study of BLV and HIV, we conclude that the carriers of these viruses are bacteria or yeast. Viruses can exist in these carriers in the intestinal and respiratory tracts for months or years. Carriers are indifferent to the fact that the virus multiplies and mutates in them. The mutant can arise in patient, and given optimal conditions, it can reproduce and spread to other individuals. However, it is possible that a new mutant may have originated in several places. It is only a matter of time before mutations appear in one virus particle. From an epidemiological point of view, it can be assumed that in the case of coronavírus variant Omicron, it could take 10 to 20 years for more than 30 mutations to occur. This coincides with the period when the first SARS-CoV-1 infection occured in 2004. Consistent with the idea that the virus can survive in an infected body for months or years in its carriers, then the Omicron ancestor can date back to the first SARS-1 epidemic.