From the environment to the cells: An overview on pivotal factors which affect spreading and infection in COVID-19 pandemic

Abstract

Several factors ranging from environmental risks to the genetics of the virus and that of the hosts, affect the spread of COVID-19. The impact of physicochemical variables on virus vitality and spread should be taken into account in experimental and clinical studies. Another avenue to explore is the effect of diet and its interaction with the immune system on SARS-CoV-2 infection and mortality rate. Past year have witnessed extensive studies on virus and pathophysiology of the COVID-19 disease and the cellular mechanisms of virus spreading. However, our knowledge has not reached a level where we plan an efficient therapeutic approach to prevent the virus entry to the cells or decreasing the spreading and morbidity in severe cases of disease. The risk of infection directly correlates with the control of virus spreading via droplets and aerosol transmission, as well as patient immune system response. A key goal in virus restriction and transmission rate is to understand the physicochemical structure of aerosol and droplet formation, and the parameters that affect the droplet-borne and airborne in different environmental conditions. The lifetime of droplets on different surfaces is described based on the contact angle. Hereby, we recommend regular use of high-quality face masks in high temperature and low humidity conditions. However, in humid and cold weather conditions, wearing gloves and frequently hand washing, gain a higher priority. Additionally, social distancing rules should be respected in all aforementioned conditions. We will also discuss different routes of SARS-CoV-2 entry into the cells and how multiple genetic factors play a role in the spread of the virus. Given the role of environmental and nutritional factors, we discuss and recommend some strategies to prevent the disease and protect the population against COVID-19. Since an effective vaccine can prevent the transmission of communicable diseases and abolish pandemics, we added a brief review of candidate SARS-CoV-2 vaccines.

Keywords: COVID-19; Cell entry; Diet; Environmental factors; Genetics factors; Vaccine.

Graphical abstract

Fig. 1

Schematic representation of SARS-CoV-2 particles as droplets and aerosols. (a–b) SARS-CoV-2 particle diameter with or without few water shells ranges from 60 to 120 nm in diameter. (c) A virus particle enveloped by ~2000 water shells is about 1 μm in diameter. (d) A droplet containing more water molecules and several virus particles ranges ~1–5 μm. (e) Human sneezing and coughing generate a large number of aerosols and droplets. The large droplets fall on the ground more than the lighter ones. Aerosol particles would float on air and survive depending on temperature and humidity as the main factors. (f) A droplet on hydrophilic surfaces with θ<π/2. (g) A droplet on hydrophobic surfaces resulting in bigger contact angle (θ>π/2) and reducing the touch area.

Fig. 2

Effects of vitamins, trace elements, gut microbiota, and Mediterranean diet on immune system function against COVID-19.

Fig. 3

Mechanisms for cell entry and possible genetic mutations in Spike protein and host receptors. (a) Possible cellular pathways for cell entry, including Spike-dependent or clathrin-mediated endocytosis. (b) Wild-type Spike protein and ACE2 receptor and their interaction. (c) Possible mutation in Spike protein which results in weaker interaction between Spike protein and ACE2 receptor. (d) A condition in which the mutation in the virus Spike protein but not ACE2 increases their interaction and eventually elevates the infection rate. (e) Possible mutations in Spike protein and ACE2 host genetic polymorphism may lead to a higher affinity, infection rate and more severe disease.