Abstract
The World Health Organization defines a zoonosis as any infection naturally transmissible from vertebrate animals to humans. The pandemic of Coronavirus disease (COVID-19) caused by SARS-CoV-2 has been classified as a zoonotic disease, however, no animal reservoir has yet been found, so this classification is premature. We propose that COVID-19 should instead be classified an “emerging infectious disease (EID) of probable animal origin.” To explore if COVID-19 infection fits our proposed re-categorization vs. the contemporary definitions of zoonoses, we reviewed current evidence of infection origin and transmission routes of SARS-CoV-2 virus and described this in the context of known zoonoses, EIDs and “spill-over” events. Although the initial one hundred COVID-19 patients were presumably exposed to the virus at a seafood Market in China, and despite the fact that 33 of 585 swab samples collected from surfaces and cages in the market tested positive for SARS-CoV-2, no virus was isolated directly from animals and no animal reservoir was detected. Elsewhere, SARS-CoV-2 has been detected in animals including domesticated cats, dogs, and ferrets, as well as captive-managed mink, lions, tigers, deer, and mice confirming zooanthroponosis. Other than circumstantial evidence of zoonotic cases in mink farms in the Netherlands, no cases of natural transmission from wild or domesticated animals have been confirmed. More than 40 million human COVID-19 infections reported appear to be exclusively through human-human transmission. SARS-CoV-2 virus and COVID-19 do not meet the WHO definition of zoonoses. We suggest SARS-CoV-2 should be re-classified as an EID of probable animal origin.
Highlights
The phenomenon of “spill-over” or “evolutionary jump” refers to the transmission of a pathogen from a natural animal host to a novel host leading to infection in the new host
The ambiguity undoubtedly needs to be addressed at greater scale, we suggest an interim solution for the classification of COVID-19 is to designate it an “Emerging infectious diseases (EIDs) of probable animal origin.”
This paper argues for a correction of the current biased narrative around zoonoses through an examination of the COVID-19 pandemic and further demonstrates that, unlike conventional zoonoses which can be relatively intractable, EID emergence has been consistently linked to human pressures on ecosystems largely through our food systems, suggesting that EIDs may be preventable [6, 10]
Summary
The phenomenon of “spill-over” or “evolutionary jump” refers to the transmission of a pathogen from a natural animal host to a novel host leading to infection in the new host. This may transpire by chance, novel exposure, repeated exposure, or key genomic change enabling the pathogen to infect the new host [1]. Infection in the new host can result in a dead-end or can lead to spread through secondary epidemiological cycling to conspecifics, or even zooanthroponotic transmission as is the case with COVID-19. In popular terminology cross-species spill-over, where it becomes established, is defined as a pathogen jump from animals to humans [1]. Spill-over is illustrated by human immunodeficiency virus (HIV) and Ebola in recent decades, and yellow fever, dengue, measles, and smallpox in the past centuries [2]
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