An Imperative Need for Research on the Role of Environmental Factors in Transmission of Novel Coronavirus (COVID-19)

I the last two decades, the emergence of viral epidemics poses great threats to human health and society. These infectious viruses have been identified as hemorrhagic fever viruses (Lassa, Ebola), novel coronaviruses including severe acute respiratory syndrome CoV (SARS-CoV), Middle East respiratory syndrome MERS-CoV), and highly pathogenic influenza. Coronaviruses (CoVs), as a class of enveloped, positive-sense single-stranded RNA virus, cause various diseases in humans. CoVs are subdivided into four groups: Alphacoronavirus, Betacoronavirus (βCoV), Gammacoronavirus, and Deltacoronavirus. Two novel βCoVs, severe acute respiratory syndrome CoV (SARSCoV) and Middle East respiratory syndrome CoV (MERS-CoV), have recently emerged and can induce a high mortality. The current outbreak of novel coronavirus COVID-19 (HCoV-19 or SARS-CoV-2), has resulted in the World Health Organization (WHO) declaring this outbreak a global pandemic. By March 15, 2020, infected cases had reached 81 048 in China and a total of 72 600 cases outside China have been reported to the WHO from 146 countries and territories (https://experience. a r c g i s . c o m / e x p e r i e n c e / 685d0ace521648f8a5beeeee1b9125cd). Similar to the SARS-CoV, symptoms of COVID-19 infection at onset of the illness include fever, myalgia, fatigue, and cough, and more than half of patients developed dyspnoea. Some patients had radiographic ground-glass lung alterations, and lower than average circulating lymphocyte and platelet populations. To date, the global deaths reached 5746, and the fatality rate was estimated as 3.7% for COVID-19 virus ( h t t p s : / / e x p e r i e n c e . a r c g i s . c o m / e x p e r i e n c e / 685d0ace521648f8a5beeeee1b9125cd), which is lower than that of SARS-CoV (10%) or MERS-CoV (37%). The major challenge of the coronavirus family and similar infectious agents is that no effective drugs or vaccine are available, and it may take many months for research and development. Human-to-human transmission of COVID-19 occurs when individuals are in the incubation stage or showing symptoms, while some individuals remain contagious while remaining asymptomatic (superspreaders). Transmission is thought to occur via touching infected surfaces (skin-to-skin, touching infected inanimate objects) then mediating the COVID-19 infection through the mouth, nose, or eyes. Transmission can also be through inhalation of exhaled virus in respiratory droplets. It has been reported that infectious viruses, including coronavirus, can survive for long periods outside of its host organism. COVID-19 virus is thought to survive for several hours on surfaces such as aluminum, sterile sponges, or latex surgical gloves, increasing the opportunity for transmission via touch. Transmission via the inhalation of small, exhaled respiratory droplets may occur as the aerosol droplets remain airborne for prolonged periods, mediating long-range humanto-human transmission via air movement. The relative contributions of large respiratory droplets, smaller airborne aerosol, or direct surface contacts to the transmissibility of COVID-19 still need to be evaluated to enable a fully effective control of transmission and infection. Faecal transmission routes should also be considered, as the COVID-19 virus has been positively detected in stool samples of infected patients. Studies have shown that SARS-CoV can