Human coronaviruses part 43

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Human SARS-CoV infection originated from the direct contact between humans and civets in market or restaurants. Closing wet markets and cleaning civets cut off  the spread chain  of SARS-CoV  and effectively  ended the SARS epidemic. In contrast, MERS-CoV is believed to have existed  in camels for a very long time and camels are widely distributed in Middle East and African countries, serving as important transport vectors  and sources of meat and milk for the local population.

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Human coronaviruses part 42

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Comparison of transmission of MERS-CoV and SARS-CoV

Both SARS-CoV and MERS-CoV are emerging zoonotic pathogens that crossed the species barriers to infect humans. Evidence showed that SARS-CoV and MERS-CoV originated from bats, the nature reservoirs, then transmitted to human via intermediate hosts civets and camels, respectively.

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Human coronaviruses part 41

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It was suggested that MERS-CoV ancestors had been circulating in bats for very long time. MERS-CoV has evolved to adapt to use human receptor and the DPP4-recognizing bat coronaviruses like HKU4 may follow up, thereby posing a serious risk to human health.

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Human coronaviruses part 40

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Although NeoCoV is closer to MERS-CoV than other bat coronaviruses at genomic level, the phylogenetic analysis of the spike protein showed that HKU4 is the most closely related to MERS-CoV among all currently known bat coronaviruses, sharing 67% sequence identity. This is  corelated with the capability of HKU4 of using DPP4 as its functional receptor. However, HKU4 preferred bat DPP4 over human DPP4, whereas MERS-CoV showed the opposite trend.

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Human coronaviruses part 39

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The most recent ancestor analysis  speculated that  MERS-CoV may have jumped from bats to camels approximately  25 years ago in Africa, with camels then being importrd into the Arabian  Peninsula, while HKU5 and MERS-CoV may have diverged from their common ancestor about 400 to 500 years ago.

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Human coronaviruses part 38

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Seven conserved replicase domains in orf1ab of MERS-CoV related viruses were compared with MERS-CoV. The concatenated translated domains of NeoCoV shared 95% amino acid sequence identity with MERS-CoV species. Other bat coronaviruses, HKU4, HKU5 and SC2013, could be considered  as different  coronavirus species

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Human coronaviruses part 37

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By genomic analysis of lineage C betacoronaviruses, MERS-CoV derived from camels show  high similarities to human MERS-CoV with>99.5% nt identities, confirming that the human and camels isolates belong to the same coronaviruses species. Bat HKU4, HKU5, NeoCoV and SC2013, shared 69.8, 70, 85.6,  and 75.6%, respectively.

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