Understanding SARS-CoV-2 features of infectivity, aggressiveness, and transmissibility: an insect-vector theory for SARS-CoV-2 dissemination

Abstract

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a ribonucleic acid–based (RNA-based) lineage B β-coronavirus characterized by 10-20 times higher infectivity and transmissibility even across species than previous coronaviruses. The significant infectivity rate of SARS-CoV-2 is due to its different host cell entry mechanisms that are mainly via angiotensin-converting enzyme 2 (ACE2) receptors contrasting earlier coronaviruses that used mainly the endosomal route. Due to the widespread distribution of ACE2 receptors throughout our body, various routes of infectivity are possible, highlighting the necessity of employing multiple forms of protection besides face masks to limit inter-human transmissibility. SARS-CoV-2 exhibits other remarkable features such as the ability to escape the immune system repeated genomic mutations that make it difficult to design a vaccine to address all viral strains and form huge host cell syncytia leading to massive tissue destruction. If we accept SARS-CoV-2 primary reservoir from bats, we should investigate the routes of viral inter-species propagation. In this article, a new theory is proposed- that the dissemination of the virus from the bats to other species and humans could have been possible via an insect vector, as insects possess significant amounts of both ACE2 receptors and a disintegrin and metalloprotease 17 (ADAM-17) enzymes that are essential for virus infectivity.
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Monkeypox in the COVID-19 era

“…In the central and West African rain forests, where monkeypox infection is endemic, an important transmission route of the virus appears to be from animal to human due to the direct contact with live animals or carcasses, scratches, bites, skin lesions caused by rodents to humans, contact with animal saliva, respiratory droplets or skin lesions, frequently occasioned by hunting and animal skinning and even consumption of inadequately cooked bush meat [4-6, 12, 15, 24, 28, 29]. However, an additional transmission route has also appeared obvious: human-to-human transmission, mainly among household members or in hospital settings [7,12]; such a transmission route requires direct, intimate contact, in contrast to the much more infective SARS-CoV-2 virus [35][36][37].…”

“…Such advanced cytopathic effects with putative sequelae can be partly explained by the central clade viral ability to block and evade the immune system mechanisms, such as the complement system, T-cells, and NK lymphocytes, inhibition of inflammatory cytokine generation, decreased NK cell chemokine receptor expression, migration capacity, and killing function, loss of cytokine secretion and immune cell degranulation functions. In this context, multiple immunomodulatory mechanisms have been described for central clade monkeypox virus: complement system inhibition via complement control protein homologs; acquisition of host immune system evasion genes; interference with the T cell receptor-mediated T-cell activation by the central monkeypox clade; suppression of the T-cell functions; inhibition of the complement enzymes; prevention of the transcription of the host immune system genes and even expression of an antibodydependent enhancement of infection [4,6,12,17,50], as in COVID-19 [36,51]. For variola virus and other poxviruses, a homologous IL-18 (interleukin 18) binding protein neutralizing human IL-18, important in the evasion from the host immune response, has been described [46] and remains to be investigated in monkeypox virus as well.…”

“…Such a contrast is due to the distinct historical timing of the emergence of the two viruses, with totally different medical research availabilities. However, even for the much-studied SARS-CoV-2, the pathogenic mechanisms and mechanisms of propagation across species are insufficiently understood [36,52,53]. Nonetheless, the preoccupation with the Monkeypox virus will gain place due to its fast geographic spread and already reported deaths outside of Africa, but also because a lot of attention is paid to the exterior aspect, such as skin scars.…”