Indoor Air Cartoon Journal, March 2020, Volume 3, #100
The COVID-19 outbreak has become a global public health and economic concern. People are worried about being infected. The concern is valid because of the potential morbidity and mortality consequences of COVID-19. Leaders of every country are making frantic efforts to reduce the risk associated with the COVID-19. Individuals also have a responsibility to reduce the risk. Thus, everyone needs to understand how to analyse the risk and make the necessary efforts required to fulfill their obligations.
It is essential to understand the contribution of virus toxicity level and concentration a person is exposed to, and the immunity level of the exposed person in fighting the virus from causing harm to the body. Firstly, there won’t be any risk if there is no exposure. The type of virus, toxicity, and concentration of a virus will not matter if a person is not exposed.
However, no exposure can be guaranteed, especially during a virus outbreak. Thus, understanding the role of the human immunity level becomes vital. Human immune systems are defense mechanisms against viruses and any other pollutants that could cause harm to the human body.
The higher the concentration and toxicity of an infectious virus that is contagious, the higher the stress that would be imposed on the immune systems of the exposed people. Immune systems would crumble if they can not withstand the stress load posed by the virus. Infection would occur as a result. A person could be exposed to COVID-19 virus (SARS-CoV-2) without being infected if their immune systems can outpower the effect of the virus concentration and toxicity level.
Continuous exposure to a virus at a concentration and toxicity level the immune system cannot handle, or decrease in immunity level to fight the virus, even if there is no more exposure to the virus, would move the consequence from infection (asymptomatic) to sickness (symptomatic).
The severity of the sickness would be more severe as the immunity level decreases. Further decrease in immunity level could eventually lead to death if there is no appropriate medical response and care to build immunity to a level that can fight the virus from causing more harm to the human body.
The moral of the story is exposure to the COVID-19 virus should be reduced as much as possible. The required preventive efforts could be at the level of governments, leaders in charge of mitigating exposure, building professionals, or individuals. More importantly, individuals should make efforts to build their immunity level to give themselves a better fighting chance against the COVID-19 virus if they are eventually exposed.
The vulnerable people with compromised immunity levels, e.g., the elderly or people with a history of health problems and complications or underdeveloped immune systems, should be given additional medical supports to build their immune systems. Mitigation of their exposures to COVID-19 virus should also be given priority.

Do you want to know more about this topic? Read Frieman et al. (2008), Lau et al. (2004), Wang et al. (2020), and Zumla et al. (2016) papers.