The coronavirus destroys the human lungs through what's called a Cytokine Storm. Cytokine storm refers to the overreaction of your body's Immune system. Cytokines are small proteins released by different types of cells in the body.

These proteins signal to immune cells to come to the site of infection. They also allow your immune cells to coordinate their response against the virus. The immune response facilitated by cytokines and immune cells triggers inflammation.

Sometimes the body produces large amounts of cytokines during an infection. This storm of cytokines causes a huge burden to your immune system forcing it to send more and more immune cells to the site infection. This leads to hyper-inflammation, which could eventually kill the patient.

The coronavirus enters into the lungs until it reaches the lower respiratory tract. That is where tiny air sacs, called alveoli, are located. Alveoli are regions in the lungs where oxygen and carbon dioxide are exchanged.

Because of the cytokine storm, the immune system begins to destroy the alveoli. More and more immune cells are recruited into the site of infection. This causes the linings of your lungs to become thicker than normal. Leading to pneumonia, an illness characterized by breathing difficulty and dry cough.

The hyper-inflammation triggered by the cytokine storm forces your immune cells to destroy healthy cells in the lining of your lungs. This makes your lungs more vulnerable to bacterial infections. Researchers called this a Secondary Bacterial Pneumonia.

Your lung could be overwhelmed by bacteria that are not normally lethal. Once your lungs become less functional by the excessive immune response. Other organs such as the liver, kidney, and brain become deprived of oxygen.

Eventually, patients require ventilators to receive enough supply of oxygen. In some cases, the immune system overcomes the cytokine storm and carefully coordinates its attack against the infection. Leading to higher chances of survival, which occurs with young COVID-19 patients.

People who are older than 60, or have a weak immune system or a pre-existing condition such as diabetes, heart disease or underwent chemotherapy treatment are less likely to survive the immune system overdrive caused by the cytokine storm.

In addition to COVID-19, researchers believe that the process of cytokine storm may have also been a major cause of mortality during the 1918 Spanish flu and the H1N1 "Swine Flu" and H5N1 "Bird Flu" of recent years.