COVID-19 was first identified late last year as a cluster of pneumonia cases caused by a new coronavirus. Doctors have since learned that it’s a respiratory disease, one that especially reaches into your respiratory tract, which includes your lungs.
COVID-19 can cause a range of breathing problems, from mild to critical. Older adults and people who have other health conditions like heart disease, cancer, and diabetes may have more serious symptoms.
Here’s what the new coronavirus does to your lungs.
Coronavirus and Your Lungs
SARS-CoV-2, the virus that causes COVID-19, is part of the coronavirus family.
When the virus gets in your body, it comes into contact with the mucous membranes that line your nose, mouth, and eyes. The virus enters a healthy cell and uses the cell to make new virus parts. It multiplies, and the new viruses infect nearby cells.
Think of your respiratory tract as an upside-down tree. The trunk is your trachea, or windpipe. It splits into smaller and smaller branches in your lungs. At the end of each branch are tiny air sacs called alveoli. This is where oxygen goes into your blood and carbon dioxide comes out.
The new coronavirus can infect the upper or lower part of your respiratory tract. It travels down your airways. The lining can become irritated and inflamed. In some cases, the infection can reach all the way down into your alveoli.
COVID-19 is a new condition, and scientists are learning more every day about what it can do to your lungs. They believe that the effects on your body are similar to those of two other coronavirus diseases, severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS).
Mild and Moderate Cases
As the infection travels your respiratory tract, your immune system fights back. Your lungs and airways swell and become inflamed. This can start in one part of your lung and spread.
Doctors can see signs of respiratory inflammation on a chest X-ray or CT scan. On a chest CT, they may see something they call “ground-glass opacity” because it looks like the frosted glass on a shower door.
About 14% of COVID-19 cases are severe, with an infection that affects both lungs. As the swelling gets worse, your lungs fill with fluid and debris.
You might also have more serious pneumonia. The air sacs fill with mucus, fluid, and other cells that are trying to fight the infection. This can make it harder for your body to take in oxygen. You may have trouble breathing or feel short of breath. You may also breathe faster.
If your doctor takes a CT scan of your chest, the opaque spots in your lungs look like they start to connect to each other.
In critical COVID-19 -- about 5% of total cases -- the infection can damage the walls and linings of the air sacs in your lungs. As your body tries to fight it, your lungs become more inflamed and fill with fluid. This can make it harder for them to swap oxygen and carbon dioxide.
You might have severe pneumonia or acute respiratory distress syndrome (ARDS). In the most critical cases, your lungs need help from a machine called a ventilator to do their job.
Some people had a cough even after they recovered from COVID-19. Others had scarring in their lungs. Doctors are still studying whether these effects are permanent or might heal over time.