COVID-19—the viral respiratory infection caused by the coronavirus SARS-CoV-2—is a rapidly evolving disease that will undoubtedly profoundly affect many, if not all, of our lives in one way or another. 

As we learn more about the disease, we can better understand how and why it affects people so differently. We don’t have a clear picture yet of why symptoms vary so much, but we do know that acute respiratory distress syndrome (ARDS) is one of the more common life-threatening complications of the infection. ARDS is when your body’s natural immune response to an infection becomes harmful to your body instead of protective. 

The lungs’ main job is to do simple gas exchange. We breathe in air and use oxygen to make energy to power all of the body’s normal functions. We breathe out carbon dioxide, which is a waste product of that energy production. This exchange is done in the alveoli, a structure in our lungs that looks like a cluster of grapes. Those grape clusters need to be surrounded by small blood vessels called capillaries to be able to bring oxygen into our body and unload the carbon dioxide we’ve been carrying in our blood. The capillaries connect what is happening in the lung to the rest of the body.

When we have an infection, an immune response that includes inflammation is triggered. Immune and inflammatory cells work together to release chemicals that cause blood vessels to become wider and “leaky.” This lets fluid and white blood cells (our immune cells) travel to the infection where they release more chemicals that tell the white blood cells to attack anything perceived as foreign. This process helps us fight the same infection faster the next time we have it.

The problem in ARDS is that when this immune response happens in the lungs, the leaking of fluid into the alveoli makes it much harder to exchange gasses. Also, the inflammatory response can change the shape of the grape-clustered alveoli until they are closed off. Then there are fewer places within the lung to do that gas exchange. All of this makes it difficult to breathe effectively. In extreme cases, people with ARDS will need to have a breathing tube placed in the lungs to help push the lungs open and deliver more oxygen (mechanical ventilation).

Older adults and people with preexisting conditions are even more susceptible because they have less strength to fight off additional infections. When faced with more than one infection at a time, the response from our own body may overwhelm us and the risk of ARDS becomes much greater.

One of the troubling aspects of COVID-19 is that it can directly cause ARDS without having to have a secondary infection first. More troubling still is that there are no real treatments for ARDS other than mechanical ventilation and time for the body to recover.

We are learning more each day about COVID-19, but it will be many months, if not years, until we have effective vaccines and treatments. That’s why we must all continue to practice effective physical distancing, frequent hand-washing and do our best to keep the vulnerable people in our communities safe.