The etiology of illness is now attributed to a novel virus belonging to the coronavirus (CoV) family, COVID-19. This new virus seems to be very contagious and spreading very rapidly with startling rate all around the globe²³. Several known coronaviruses are circulating in animals and most of them have not yet infected humans. The SARS-CoV-2 is also known as β-coronavirus, which is enveloped non-segmented positive-sense ssRNA virus (subgenus sarbecovirus, Orthocoronavirinae subfamily) ²⁴. CoV are divided into four genera, including α, β, γ and δ-CoV in which α- and β-CoV are associated to infect the mammals, while γ- and δ-CoV able to infect birds. Previously, six CoVs have been identified as human-susceptible virus with low pathogenicity and cause mild respiratory symptoms similar to common cold viz; α-CoVs, HCoV-229E,HCoV-NL63, β-CoVs, HCoV-HKU1 and HCoV-OC43. The other two known SARS-CoV and MERS-CoV lead to severe and potentially fatal respiratory tract infections²⁵. Genome sequence analysis revealed that SARS-CoV-2 was 96.2% identical to bat CoV RaTG13, whereas it shares 79.5% identity to SARS-CoV. Based on virus genome sequencing and evolutionary analysis, bat has been suspected as natural host of SARS-CoV-2 virus origin and might be transmitted from bats via unknown intermediate hosts to infect humans. SARS-CoV-2 use angiotensin-converting enzyme 2 (ACE2) as target receptor, the same as SARS-CoV²⁶.

The COVID19 genomic analysis provides the clues about its origin. During an outbreak in China province a COVID19 genetic code may steadily mutate as it spreads through a population. The mutations are slight often just a single letter change in the code, like from AATC to ATTC. The mutations provide a time and geographical stamp of sorts. Acute respiratory tract infection first appeared in Wuhan, China, possibly related to a seafood market since 12 December 2019. Various ongoing research studies revealed that bat may be the potential source of SARS-CoV-2^27,28. However, there is no evidence so far that the origin of SARS-CoV-2 was from the seafood market. From its first appearance in china COVID19 has spread to more than two hundred other countries including Asia, Europe, North America, South America, Africa, and Oceania etc²⁹. At present, COVID19 is spreading rapidly from human to human contact through air droplet transmission in all these regions^30,31. COVID19 was designated as a public health emergency by the WHO and on 11 March 2020, declared as a pandemic^32,33. Genomic epidemiology of hCoV-19 in Guangdong Province, China reported that the genome sequences from Guangdong are interspersed across the COVID-19 outbreak phylogeny. The Guangdong sequences substantially extend the known genetic diversity of hCoV-19 genomes from China³⁴. Furthermore, sequencing of COVID19 study from other geographical reasons will very likely increase this diversity further.

COVID-19 is transmitted person-to-person via close contact with one another (within about 6 feet), through respiratory droplets produced from coughing or sneezeing of infected person. These droplets may land in the mouth, nose, and eyes of nearby people and possibly reach lungs by inhalation ³⁵. Asymptomatic carrier transmission has been reported for SARS-CoV-2³⁶; hence, anyone if found having close contact with infected persons should be quarantined for specified incubation period and then hospitalized on the basis of positive test (PCR) result only³⁰. Although, the extent to which this occurs remains unknown, a large-scale serologic screening test may be able to provide a better sense of asymptomatic infections and inform epidemiologic analysis. Recently, Cai et al 2020³⁷ have reported that indirect transmission of the causative virus occurred and suspected via resulting from virus contamination of common objects, virus aerosolization in a confined space, and spread from asymptomatic infected persons (Fig-2). According to U.S. National Academies of Science, COVID-19 may spread through the air in tiny particles that infected people exhale during normal breathing and speech. “Currently available research supports the possibility that SARS-CoV-2 could be spread via bio-aerosols generated directly by patients’ exhalation ^38-40. Therefore, it can be said that SARS-CoV-2 can survive outside the body for long time and spread rapidly via various fomites (e.g., elevator buttons or restroom taps, metro handrails, public transport, common hand wash facility and via currency) or virus aerosolization in a confined public space (e.g., restrooms or elevators).