Over the past two decades, coronavirus-associated diseases such as SARS
and MERS have challenged the public health systems globally. Around 2002-2003, a
near-pandemic of a previously unknown β-coronavirus, named SARS-CoV, arose in
China and 29 other countries. Not much attention was paid to it post-disappearance of
this outbreak. An understanding of the coronavirus began only after alarming
predictions of the virus’s re-emergence began in 2007. Identification from previous
studies revealed that bats have proven to be a major reservoir of animal coronavirus.
SARS-related bat coronaviruses have all the essential components of SARS-virus, have
along with similar genome sequences to that of SARS-CoV and SARS-CoV-2, and
thus, are able to cause infection and transmit between humans directly. Later in 2012,
another unknown β-coronavirus named Middle East respiratory syndrome (MERSCoV), with close relation to the SARS-CoV, caused an epidemic limited to the MiddleEast. The emergence of yet another bat-origin coronavirus, α-coronavirus, in China
caused epizootic disease in pigs, thus named swine acute diarrhea syndrome
coronavirus (SADS-CoV). Subsequently, unattended warnings of 12 years led to the
most fatal bat-derived sarbecovirus, recognized as SARS CoV-2, springing up in
November 2019, sweeping the globe. The predictions of SARS-CoV-2 to be a natural
event with association to transmission directly from bats to humans or through an
intermediate host have been essentially proven to be true. SARS-Cov-2 shares genetic
properties with many other sarbecoviruses; this slies fully within their genetic cluster
and is, thus, a naturally emerged virus.
Based on the genomic structure coronavirus is mainly divided into four subgroups
alpha, beta, gamma, and delta.
CoVs are fall under the family Coronaviridae, and subfamily Orthocoronavirinae. The
virus is protected by receptor binding domain (RBD) that binds to ACE2 receptor
found in kidneys, lungs, heart and gastrointestinal tract, which that promote viral entry
into target cells.
Domestic animals can act as intermediary hosts in the transmission of viruses from
natural hosts to people. Porcine Epidemic Diarrhea CoV(PEDC), which originated in
pigs, was found to be similar to SADS-CoV. It has been transferred from bats to pigs.
SADS-CoV was first found in rhinolophids or horseshoe bat, before the SARS
epidemic Recombination of bat SARSr-CoVs, or recombined virus, infected and
adapted to civets and humans. MERS-CoV is a zoonotic virus. It was transferred from
dromedary camels to humans. The first confirmed cases of SARS-CoV-like viruses
were found in raccoon dogs in live animal markets and palm civets. Another bat
coronavirus, CoV RaTG13, was isolated from the Rhinolophus affinis bats.
Corona variants are classified into variants of concern (VOCS), variants of interest
(VOI), variants of high consequence (VOHC), and variants being monitored (VBM).
Some common coronaviruses of human are 229E, NL63, OC43, and HKU1, which
infect the upper-respiratory tract.
Keywords: ACE2 receptor, A570Y, ARCoV-2, APN, AIBV, BALF, CTD, CEACAM1, CoV-HKU5 strains, D614G, DPP4, Fatal pneumonia, GISAID, HCoV, HKU1, HCoV-OC43, MERS-CoV, NL63, N5014, Nsp, NTD, Orthocoronavirinae, Orf1a, PL-pro, PEPV, RaTG13, Rf4092, RBd, SARS-CoV-2, Spike (S1), SARS-CoV, SADS-CoV, SARsr-CoVs, TMPRSS2, TCOV(TECoV), TGEV, VOI, VBM, VOCs, VOHC, WIV16.
