Speculation is that this report from India is correct: the earliest SARS-CoV-2 ancestor was from a pig rather than a bat.
Dec 2020 India / Zoonotic Evolution
The outbreak and spread of new strains of coronavirus (SARS-CoV-2) remain a global threat with increasing cases in affected countries. The evolutionary tree of SARS-CoV-2 revealed that Porcine Reproductive and Respiratory Syndrome virus 2, which belongs to the Beta arterivirus genus from the...
pubmed.ncbi.nlm.nih.gov
’....The evolutionary tree of SARS-CoV-2 revealed that Porcine Reproductive and Respiratory Syndrome Virus 2 (PRRSV-2), which belongs to the beta Arterivirus genus from the Arteriviridae family is possibly the most ancient ancestral origin of SARS-CoV-2 and other Coronaviridae.’
Minnesota now being the U.S. hotspot for the Delta variant, links to Minnesota PRRSV:
Ap 1992 University of Minnesota Department of Veterinary Diagnostic Medicine
A recent epizootic of swine infertility and respiratory syndrome (SIRS) in a Minnesota swine herd was investigated. Examination of a sow, neonatal piglets, and stillborn fetuses obtained during the epizootic from the affected herd revealed interstitial pneumonitis, lymphomononuclear...
pubmed.ncbi.nlm.nih.gov
’A syndrome of reproductive failure and respiratory disease of unknown etiology was first recognized in 1987-1988 in swine herds in North Carolina, Iowa, and Minnesota. A similar syndrome has been recognized in Germany, The Netherlands, England, Belgium, and Spain.’
1989 Indiana: PRRSV Outbreak
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’....An outbreak of Porcine Reproductive and Respiratory Syndrome (PRRS), formerly called swine infertility and reproductive syndrome or mystery swine disease, occurred on 18 farms in Wabash County, Indiana, in spring of 1989. An extensive diagnostic investigation conducted at Purdue Animal Disease Diagnostic Laboratory and diagnostic testing at a number of other laboratories did not result in a conclusive etiologic diagnosis.’
’Retrospective serological studies indicate that PRRSV first appeared in North America in 1979, in Asia in 1985, in Europe in 1987, and the virus was subsequently disseminated to swine populations throughout the world. PRRSV is most similar genetically to LDV (lactate dehydrogenase-elevating virus).’
(MacLachlan NJ, et al, Arterivirus Pathogenesis and Immune Response, Ch. 21, Nidoviruses, ASM Press, Washington, D.C. 2008)