COVID-19 can damage several parts of the body, but most people experience symptoms in their respiratory tract, with a sore throat, stuffy nose, cough or shortness of breath. Some of these symptoms, specifically coughing and shortness of breath, originate in the lungs.
“It may feel like a cold, a bad cold,” said Gopal Allada, M.D., an Oregon Health & Science University pulmonologist.
But some people experience shortness of breath or a cough that lingers for weeks. In extreme cases, someone might need a ventilator to help them breathe. So how does COVID-19 affect your lungs?
Lung anatomy and breathing
Your lungs are spongy organs that breathe in oxygen. Their “main jobs are to get oxygen into our body and to get rid of carbon dioxide, which is the waste product—the exhaust of the body,” Allada said.
Every part of your body needs oxygen — the brain, digestive system, internal organs, muscles and joints. Think of your body like a car that uses fuel to run and “exhales” exhaust from its tailpipe. That exhaust – the carbon dioxide (CO2) – is created in your blood stream.
Inside your lungs are millions of tiny air sacs called alveoli. These sacs are covered in tiny blood vessels called capillaries. When you inhale, the air sacs fill with oxygen which travels through the air sac walls into capillaries and outward in your body’s blood stream.
When you exhale, the reverse happens. Instead of oxygen traveling through your blood stream, CO2 moves from your blood stream into the air sacs, through your lungs, windpipe and out your mouth.
A COVID-19 infection can block oxygen from getting into your blood stream and block CO2 from getting out, making it hard to breath and hard for oxygen to reach the rest of your body.
COVID-19, your immune system and your lungs
When the COVID-19 virus infects your cells, it makes copies of itself, and the copies infect more cells. That’s when your body’s immune system jumps into action.
“Our bodies have a great innate immune system that recognizes ‘Hey this is an infectious critter, and my job is to create an immune response,’” Allada said.
Among other immune responses, the cells in your lungs start to create mucus as a barrier between the virus and your cells. This response helps get rid of some virus, but it also leads to symptoms like coughing. Another immune response is inflammation, which helps immune cells reach the places the virus is attacking.
Unfortunately, the immune responses can also cause harm.
“The immune system does what it thinks is right, helping attack the virus,” Allada said. “But sometimes inflammation goes awry and the air sacs fill with fluid.”
When the alveoli sacs fill with fluid, oxygen can’t get to your blood. If the air sacs continue to fill with fluid, that can lead to pneumonia. And too much mucus can lead to a persistent cough and bronchitis. People who get COVID-19 can experience a persistent cough for months.
If pneumonia progresses and the air sacs fill with fluid, a person can develop an extremely dangerous condition called Acute Respiratory Distress Syndrome (ARDS). Someone with ARDS has so much difficulty breathing they need an external source of oxygen, such as a ventilator. ARDS can be fatal.
Working lungs are the only way our body can receive oxygen, so it’s important to protect them. Avoid smoking or vaping and consider wearing a KN95 or N95 mask when in crowded situations, both indoors and outside.
The best way to protect yourself from COVID-19 is by getting all the recommended vaccine and booster doses for which you are eligible. Additionally, if you have conditions such as chronic lung disease or chronic obstructive pulmonary disease (COPD) you could be eligible for COVID-19 treatments, such as antivirals or monoclonal antibodies.