The most eagerly awaited summer of the Anthropocene: A perspective of SARS-CoV-2 decay and seasonal change.

To date, the world perhaps has never waited for the summer so impatiently in the entire Anthropocene, owing to the debate whether increasing temperature and humidity will decrease the environmental endurance of SARS-CoV-2. We present the perspective on the seasonal change on SARS-CoV-2 decay and COVID-19 spread. Our arguments are based on: i) structural similarity of coronavirus with several enteric viruses, and its vulnerability; ii) reports related to decay of those similar transmissible gastroenteritis viruses (TGEV) like norovirus and iii) improvement in the human immunity during summer compared to winter. We present reasons why we can be optimistic about the slowdown of corona in the upcoming summer.

Perspective

Till date, the world perhaps has never waited for the summer so impatiently in the entire Anthropocene, owing to the debate whether increasing temperature and humidity decrease environmental endurance of SARS-CoV-2. It is firmly established that in the water environment, viruses become less prevalent in summer owing to high temperature and solar radiation, leading to decline in flu patient numbers during summer (van der Hoek et al., 2004; University of Cambridge, 2015; Gundy et al., 2009; Hamza et al., 2011; Carratala et al., 2013). Thus, increase of both temperature and biological activities (both inside and outside the human gut) in summer is likely to reduce COVID-19 prevalence.

As per the inactivation mechanism, environmental stressors disrupt the proteins and lipids of viral envelope more easily than the genome and the protein capsid (Pinon and Vialette, 2018). Thus, under the similar adverse conditions, non-enveloped viruses, like norovirus, are generally more resistant than enveloped viruses like SARS-CoV-2 (positive-stranded RNA viruses with nucleocapsid and envelope) (University of Cambridge, 2015; Gundy et al., 2009). A decline in infections in summer has been reported umpteen times for transmissible gastroenteritis viruses (TGEV) like norovirus, which are antigenically and genetically related (van der Hoek et al., 2004) to certain respiratory coronavirus (van der Hoek et al., 2004; University of Cambridge, 2015; Gundy et al., 2009). No wonder, current spread of COVID-19 along the equator and tropics has been significantly less (Dong et al., 2020).

Unlike TGEV, the main transmission pathway of SARS-CoV-2 is respiratory droplets, not water (Gorman, 2020). Still we can remain optimistic about the endurance declination of COVID-19, as human immunity increases in the summer owing to favourable seasonal variation in the genetic activities, blood composition and adipose tissue (van der Hoek et al., 2004; University of Cambridge, 2015; Castro Dopico et al., 2015; Donnelly, 2015). Nevertheless, factors like carrier prevalence, treatment efficacy of wastewater burden (virus source), and level of spread, will remain critical variables (Zhang et al., 2020; Wu et al., 2020; Sims and Kasprzyk-Hordern, 2020). Overall, at this juncture, we just intend to point out that in this crisis we should not lose faith on scientific facts and principles logics which strongly suggests COVID will not endure high temperature and humidity of the (Indian/Tropical) summer.