Emerging novel coronavirus (2019-nCoV)—current scenario, evolutionary perspective based on genome analysis and recent developments

Malik, Yashpal Singh; Sircar, Shubhankar; Bhat, Sudipta; Sharun, Khan; Dhama, Kuldeep; Dadar, Maryam; Tiwari, Ruchi; Chaicumpa, Wanpen

Coronaviruses (CoVs) are well-known causes of severe infections, respiratory, enteric and systemic, in humans and numerous animal hosts. The CoV infections have been reported in cattle, swine, horses, camels, rodents, cats, dogs, bats, palm civets, ferrets, mink, rabbits, snake, and several other wild animals and avian species (Fehr and Perlman 2015; Kahn and McIntosh 2005) . The coronaviruses of relevant veterinary species are shown in Table 1 with organ affected and clinical signs. Though human CoVs were identified for the first time in the year 1960 from respiratory infections in adults as well as children, the major scientific interest in CoVs research grew only after the emergence of Severe Acute Respiratory Syndrome CoV (SARS-CoV) in the year 2002 (Drosten et al. 2003 Ksiazek et al. 2003; Peiris et al. 2003) . In this SARS-CoV epidemic, around 8000 confirmed human cases with 774 deaths (around 9.5% mortality rate) occurred that was a result of its global spread (Kahn and McIntosh 2005) . Initially, the virus was detected in the caged Himalayan palm civets and these were thought to be the natural host of this virus . Following SARS-CoV incidence in 2003, a similar CoV named HKU3-1 to HKU3-3 were identified in the horseshoe bats (non-caged) in 2005 from Hong Kong (Lau et al. 2005) . Since then, bats are considered to be the natural host and potential reservoir species that could be held responsible for any future CoVs epidemics and/or pandemics (Cui et al. 2019 . After the 2003 and 2005 SARS-CoV epidemics, an analogous virus emerged in the Middle East region of the world leading to severe respiratory illness and was named the Middle East Respiratory Syndrome CoV (MERS-CoV) (Zaki et al. 2012 ). The mortality was higher than previous SARS-CoV pandemic claiming around 919 lives out of the total 2521 human cases (around 35% mortality) (World Health Organization 2015) . Notably, dromedary camels were connected with the transmission of MERS-CoV (Alagaili et al. 2014) . Further, its origin was also traced from bats (Ithete et al. 2013 ). All these highly pathogenic human CoVs, SARS and MERS, show emergence over wider areas of the world posing high risk of human-to-human transmission and fatal consequences thereto (Figure 1 ). This decade's first CoV emergency was from Hubei province of China, and as on February 4, 2020, 425 deaths have been reported in China only (World Health Organization 2020b). Further, the spread of this novel coronavirus, named 2019-nCoV, has been noted in 24 countries till date. Considering the global threat of the 2019-nCoV, the World Health Organization (WHO) declared it as a 'Public Health Emergency of International Concern' on January 30 th , 2020.