Abstract
The current Coronavirus Disease 2019 (COVID-19) pandemic, with more than 111 million reported cases and 2,500,000 deaths worldwide (mortality rate currently estimated at 2.2%), is a stark reminder that coronaviruses (CoV)-induced diseases remain a major threat to humanity. COVID-19 is only the latest case of betacoronavirus (β-CoV) epidemics/pandemics. In the last 20 years, two deadly CoV epidemics, Severe Acute Respiratory Syndrome (SARS; fatality rate 9.6%) and Middle East Respiratory Syndrome (MERS; fatality rate 34.7%), plus the emergence of HCoV-HKU1 which causes the winter common cold (fatality rate 0.5%), were already a source of public health concern. Betacoronaviruses can also be a threat for livestock, as evidenced by the Swine Acute Diarrhea Syndrome (SADS) epizootic in pigs. These repeated outbreaks of β-CoV-induced diseases raise the question of the dynamic of propagation of this group of viruses in wildlife and human ecosystems. SARS-CoV, SARS-CoV-2, and HCoV-HKU1 emerged in Asia, strongly suggesting the existence of a regional hot spot for emergence. However, there might be other regional hot spots, as seen with MERS-CoV, which emerged in the Arabian Peninsula. β-CoVs responsible for human respiratory infections are closely related to bat-borne viruses. Bats are present worldwide and their level of infection with CoVs is very high on all continents. However, there is as yet no evidence of direct bat-to-human coronavirus infection. Transmission of β-CoV to humans is considered to occur accidentally through contact with susceptible intermediate animal species. This zoonotic emergence is a complex process involving not only bats, wildlife and natural ecosystems, but also many anthropogenic and societal aspects. Here, we try to understand why only few hot spots of β-CoV emergence have been identified despite worldwide bats and bat-borne β-CoV distribution. In this work, we analyze and compare the natural and anthropogenic environments associated with the emergence of β-CoV and outline conserved features likely to create favorable conditions for a new epidemic. We suggest monitoring South and East Africa as well as South America as these regions bring together many of the conditions that could make them future hot spots.
Highlights
The current pandemic of Coronavirus Disease 2019 (COVID19; Zhu et al, 2019; Guan et al, 2020), which has caused an estimated 2,500,000 deaths to date, is only the latest example that viruses sometimes leave their sylvatic environment to accidentally infect humans
There is no evidence that a CoV from a Latin American bat has been circulating among the inhabitants of this region, even at a low level, below the clinical detection threshold
Coronaviruses in South America are spreading among unrelated bat species four times less than in Africa, which could be linked, either to disparate bat species interactions in different regions, or to genetic differences in CoVs (Anthony et al, 2017b)
Summary
The current pandemic of Coronavirus Disease 2019 (COVID19; Zhu et al, 2019; Guan et al, 2020), which has caused an estimated 2,500,000 deaths to date, is only the latest example that viruses sometimes leave their sylvatic environment to accidentally infect humans. The only way to counteract this threat is to accumulate knowledge about viruses, their hosts and their dynamic of transmission, identify regions with the characteristics of potential hot-spots, and improve regional monitoring and develop warning and intervention tools To this end, it is important to explore the dynamic of CoVs in wildlife and the reasons for their transfer to humans. A new classification has recently been proposed by ICTV (2020b) According to this new classification, SARS-CoV is positioned as follows: realm Riboviria, order Nidovirales, suborder Comidovirineae, family Coronaviridae, subfamily Orthocoronavirinae, genus Betacoronavirus, subgenus Sarbecovirus, species Severe acute respiratory syndrome-related coronavirus, and MERS-CoV is assigned to the genus Betacoronavirus, subgenus Merbecovirus. The CoVs that have emerged in humans over the last twenty years and are suspected to originate from wildlife, all belong to the βCoV genus, either to lineage A/currently subgenera Embecovirus (HCoV-HKU1), lineage B/Sarbecovirus (SARS-CoV and SARSCoV-2), or lineage C/Merbecovirus (MERS-CoV) (ICTV, 2020b). The only batCoV sequence ever found to be identical to that of human CoV is the RNA-dependent RNA polymerase (RdRp) gene of the MERS-CoV sequenced from T. perforatus in Saudi Arabia
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