What you may not know about coronavirus — the disease that has reached pandemic proportions — is that one of the times you are most vulnerable to contracting it is while you’re sleeping. Here is how this can happen, and what you can do about it.
Coronavirus infects cells below the voice box, in the airways and deep in the lungs, unlike flu viruses which start with your nose and throat. Other than via tiny particles inhaled in air, coronavirus reaches those cells via fluid in the nose or throat that sneaks past your voice box (this is called aspiration) and slides down your windpipe, or trachea.
Studies have shown that at least half of normal people — young, middle-aged, elderly — aspirate at night during sleep. By the end of a week, probably we all have. After taking a sleeping pill or a couple beers or shots — and sleeping more deeply — the chance of aspiration is even higher. And as we age, ordinary swallowing often becomes less well coordinated.
If you have lung damage from smoking, swallowing saliva, which we all do while we sleep, can deliver even more aspirated throat contents into the lungs. The amount of fluid aspirated during sleep is enough to cause pneumonia — in fact, it’s how most pneumonia occurs.
So why don’t we wake up with pneumonia every morning? First, most of our noses and throats carry safe bacteria, not microbes like coronavirus that can cause pneumonia. Second, our deep lung has some cells that kill microbes that arrive there.
Lastly, healthy people have a robust system for transporting the aspirated viruses and bacteria up the windpipes and dropping it in the esophagus, where it is swallowed and begins to be digested with the saliva we make. Some people get mild diarrhea from this virus because it can infect cells in your gut, too.
Daytime (waking) aspiration, such as when food goes down the wrong pipe, is coughed up — if you have a normal cough reflex and a strong cough. Each of these protective factors for relatively young and healthy people can be impaired with lung disease and advancing age.