Recent studies have reported that about 80% of people infected with SARS-CoV2 are asymptomatic, it means they are "silent carriers". These patients show no or very mild symptoms. As it is known that viruses need to get into living cells to divide and survive. Same applies with SARS-CoV2, this virus attaches its spike protein present on the outer shell with the human cell's protein receptor, called Angiotensin converting enzyme 2 (ACE2). These ACE2 receptors are normally found in the lungs, kidneys, heart and gut. After getting infected with this virus, it take incubation period of about 14 days for symptoms to arise. Having healthy immune system during this incubation period can reduce the viral load and thus prevent it from entering the lungs.

Our immune system provides us two lines of defense. First one is innate component including physical barriers such as skin and mucosal membranes, variety of proteins and some of the white blood cells for attacking foreign material. This immune response is non-specific and works fast. The second component is adaptive component. This works slowly but is specific for particular infection and holds memory of infection.

Specific genetic variations in humans might also play role in determining the intensity of sickness. By producing fast adaptive immune response, the body may recognize virus early and work against it. General health also determines the immune response.

If SARS-CoV-2 virus still survives during this entry to the body, it makes entry into lungs via mucosal respiratory tract. There it binds to ACE2 receptors and replicates further, which triggers immune response. The amount of virus which one gets into lungs also determines severity of sickness.

In many patients, the immune response is intense which results in "cytokine storm". Cytokines are proteins that act as signals to generate immune response. This can lead to excessive inflammation which can cause organ damage and can be fatal.

(Via:  https://www.youtube.com/watch?v=UGxgNebx1pg&list=PLQ_IRFkDInv-NvRRUN0aqe51sMs188k8z&index=58&t=0s

https://www.youtube.com/watch?v=AToF8O5T86s&list=PLQ_IRFkDInv-NvRRUN0aqe51sMs188k8z&index=25&t=396s

https://www.youtube.com/watch?v=qqZYEgREuZ8&list=PLQ_IRFkDInv-NvRRUN0aqe51sMs188k8z&index=49&t=274s

https://www.youtube.com/watch?v=1vZDVbqRhyM&list=PLQ_IRFkDInv-NvRRUN0aqe51sMs188k8z&index=27&t=0s)

Recent studies have reported that about 80% of people infected with SARS-CoV2 are asymptomatic, it means they are "silent carriers". These patients show no or very mild symptoms. As it is known that viruses need to get into living cells to divide and survive. Same applies with SARS-CoV2, this virus attaches its spike protein present on the outer shell with the human cell's protein receptor, called Angiotensin converting enzyme 2 (ACE2). These ACE2 receptors are normally found in the lungs, kidneys, heart and gut. After getting infected with this virus, it take incubation period of about 14 days for symptoms to arise. Having healthy immune system during this incubation period can reduce the viral load and thus prevent it from entering the lungs.

Our immune system provides us two lines of defense. First one is innate component including physical barriers such as skin and mucosal membranes, variety of proteins and some of the white blood cells for attacking foreign material. This immune response is non-specific and works fast. The second one is adaptive component. This works slowly but is specific for particular infection and holds memory of infection.

Specific genetic variations in humans might also play role in determining the intensity of sickness. By producing fast adaptive immune response, the body may recognize virus early and work against it. General health also determines the immune response.

If SARS-CoV-2 virus still survives during this entry to the body, it makes entry into lungs via mucosal respiratory tract. There it binds to ACE2 receptors and replicates further, which triggers immune response. The amount of virus which one gets into lungs also determines severity of sickness.

In many patients, the immune response is intense which results in "cytokine storm". Cytokines are proteins that act as signals to generate immune response. This can lead to excessive inflammation which can cause organ damage and can be fatal.

(Via: 
https://www.youtube.com/watch?v=UGxgNebx1pg&list=PLQ_IRFkDInv-NvRRUN0aqe51sMs188k8z&index=58&t=0s

https://www.youtube.com/watch?v=AToF8O5T86s&list=PLQ_IRFkDInv-NvRRUN0aqe51sMs188k8z&index=25&t=396s

https://www.youtube.com/watch?v=qqZYEgREuZ8&list=PLQ_IRFkDInv-NvRRUN0aqe51sMs188k8z&index=49&t=274s

https://www.youtube.com/watch?v=1vZDVbqRhyM&list=PLQ_IRFkDInv-NvRRUN0aqe51sMs188k8z&index=27&t=0s)