How does SARS-CoV-2 affect the lungs?
SARS-CoV-2 gets into our cells by attaching to a protein that is found on the surface cells throughout the body. This protein called ACE2 receptor is distributed very heavily on cells throughout the lungs and our blood vessels. As the virus gets into and out of these cells the lining of tubes that go into our lungs gets damaged. The lining of the respiratory tract can become inflamed and swollen. Small blood vessels in the lungs can be affected and tiny little blood clots may develop. ACE2 proteins are on cells that are important for the functioning of the tiny little thin air sacs called alveoli where oxygen is absorbed and carbon dioxide comes out of the blood to be exhaled. Having these tiny little air sacs working well is essential for the efficient exchange of gases through the alveolar membrane and through the walls of the network of tiny little blood vessels around the alveoli.
People who have severe COVID-19 will often have what is called ARDS (acute respiratory distress syndrome). There are many different processes going on in ARDS that result in the body becoming starved of oxygen. One of the most disastrous things that occurs is that because of widespread inflammation and other processes fluid and other substances can fill up the space between the alveoli and the surrounding capillaries. This acts as a barrier to the diffusion of gases. Once this happens COVID-19 can be very difficult to treat.
There has been some research suggesting that the Omicron variant may replicate slower in the deeper parts of the lungs than the Delta variant. That is encouraging, but it is important to note that this data comes from researchers using cell cultures and others experimenting with mice and hamsters. It is not clear if what is happening in cell cultures and animals will reflect what occurs in humans. While we hope it is true that the Omicron variant will cause less damage in the lungs people are still being hospitalized and dying from being infected with the Omicron variant.
In the next article in this series, I will share information about how the virus affects other systems in the body.
Information presented in these articles is intended to provide a medical perspective - the articles are not intended as a political statement for or against any public policy. Statements in these articles should be considered coming from myself, not from any organization I represent or my employer.
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