Environmental toxicities might encourage susceptibility to COVID-19 pandemic: A brief commentary
Authors: Joystu Dutta, Tirthankar Sen, Sufia Zaman, Abhijit Mitra, Priya Sharma
DOI: 10.87349/JBUPT/281003
Page No: 14-25
Abstract
COVID 19 or Novel Coronavirus is a near unstoppable killer and is an emerging and rapidly evolving medical emergency situation across the globe. This gigantic viral outbreak was declared to be a Public Health Emergency of an international concern on January 30, 2020. World Health Organization (WHO) has declared the novel coronavirus disease, COVID-19 (2019- nCOV) to be a global pandemic on March 11, 2020 and until April 8, 2020, 5:30 GMT 5:30, it has reported 1, 317, 130 confirmed cases of SARS-COV 2 infections worldwide with 74, 304 confirmed deaths and 212 countries, areas and territories affected by the viral outbreak of unprecedented nature. This apocalyptic global public health emergency scenario started with a reporting of pneumonia with an unknown cause in WHO country office located in Wuhan, Hubei province in People’s Republic of China (PRC) on December 31, 2019.The clinical characteristics of the infection are very similar to viral pneumonia. Respiratory sample analysis by PRC Centers for Disease Control (CDC) confirmed that the infection is related to Novel Coronavirus Pneumonia (NCP) and was caused by Coronavirus (Huang, et al., 2019). WHO officially named this viral outbreak as COVID-19 and International Committee on Taxonomy of Viruses (ICTV) ascribed it as SARS-COV-2, the abbreviation for Severe Acute Respiratory Syndrome Coronavirus-2, a member of large β – coronavirus family widely prevalent in nature. The extremely high transmissibility and infectivity despite of comparatively low mortality rates makes SARS-COV-2 a unique member of the family with SARS and MERS (Liu, et al., 2020). The crude mortality ratio (the number of reported deaths divided by the number of reported cases) is between 3-4% while the infection mortality rates (the number of reported deaths by the number of infections) is comparatively lower (COVID-19 Situation Report- 46, WHO). COVID-19 and influenza viruses have similar disease representation but the speed of transmission is entirely different between the two. Influenza has shorter median incubation period (time from infection to appearance of symptoms) and shorter serial interval of just three days (the time between successive cases) in comparison to COVID- 19 with a serial interval of five to six days. The basic reproductive number R0 (the number of secondary infections generated from a single individual in completely susceptible populations without any interventions) is much higher in COVID-19 (2-2.5) with respect to influenza. However, (Wu, et al., 2020) estimated R0 of SARS-CoV-2 to be (2.47-2.86) while that of SARS-CoV is (2.2-3.6) (Lipsitch, et al., 2003) and MERS-CoV is (2.0-6.7) (Majumder, et al., 2014). This indicates high transmissible character of (2019 n-CoV). The median age of population susceptible to SARS-COV-2 is 47.0 years however the numbers are rapidly changing worldwide as new areas are being covered by the viral outbreak (Guan, et al., 2020; Wu, et al., 2020). Source of infection, routes of transmission and susceptibility are three major epidemiological parameters of Coronavirus family (Barreto, et al., 2006) and finds no exception in COVID 19. The nature and pathogenic representations between these epidemiologically linked viral diseases are contextual and time-specific making direct comparisons an uphill task for researchers worldwide. Genome analysis conclusively claimed that novel coronavirus (SARS-COV-2) has emerged from bat SARS Coronavirus (SARSr-CoVRaTG13) with complete genome recognition rates of 79.5% and 96% respectively (Chen, et al., 2020). This finding finds basis as the detection of Group 1 Coronaviruses in bats were initially observed in North America by (Dominguez, et al., 2007). SARS-CoV-2 isolated from pangolins and the viral strains currently infecting humans show 99% similarity as per macrogenomic sequencing analysis performed by (Xu, et al., 2020). Emerging diseases such as COVID- 19 are majorly zoonoses caused by ss-RNA viruses (Woolhouse, 2002; 2005). They lack proof-reading activity and show spontaneous mutation and sporadically jump across the species defying all rules of evolutionary principles. The case in evidence is the COVID-19 infection of big cats (tigers and lions) of Bronx Zoo from the zookeeper who tested positive. Human to animal routes of viral transmission is not only rare but striking.
