What you really need to know during this pandemic is how risky different behaviors are. Although I’m not a public health worker, I’m a scientist who, for 26 years, studied how respiratory pathogens cause diseases. Whether it’s a virus, bacterium, fungus or protozoan, it has to get into the respiratory tract. This can happen directly when you inhale droplets exhaled by an infected individual who is very nearby. What’s more, numbers matter. The more particles you inhale, the more apt you are to get infected. For most pathogens, inhaling just a few won’t hurt you, but if you inhale more, you may get sick faster or even get a worse case of the disease.
As for contaminated surfaces, remember that viruses can’t move around on their own. Think of them like glitter. If a “glittered” person pats your dog, the glitter won’t move to another part of a dog’s fur, although the dog might shake it off when it scratches or spread it around by licking. Again, when touching that dog or anything else, it’s still a numbers game. You’re unlikely to remove all that glitter with a single touch, but you still might want to wash your hands, or discourage the interaction in the first place.
There is scientific evidence that some viruses can move from your eyes into your respiratory tract. You may have noticed this drainage path if you ever used eye drops and had to blow your nose a few minutes later. By washing your hands and avoiding touching your face, you keep from rubbing virus into your eyes and nose. Since most people don’t wash their faces as often as their hands, glitter might remain there ready to be rubbed around for a while. Health care workers need goggles or face shields and masks in case infected patients cough, breath or sneeze on them repeatedly or for prolonged periods. Because of the numbers game, just walking past someone in the grocery store or on a sidewalk or standing six feet away from someone doesn’t put you at enough risk to benefit from a mask.
Putting food in your mouth and swallowing it is not a very efficient way for a pathogen to get into the respiratory tract, especially since the chemical makeup of the saliva may help break down the virus. However, when people eat, they often wipe their mouths and touch other parts of their faces. Hence the advice to wash those hands before you eat.
Understanding open and closed systems helps to understand the social distancing advice. Most situations on planet Earth are to some degree open systems in which people and things move in and out of contact with one another. A tightly closed system would be like astronauts in a space capsule where nothing and no one from the outside can get in. So minimizing contact achieves a more closed, less risky setting. Being outside is fine, especially if it’s a sunny day since the sun’s ultraviolet light helps inactivate viruses. Delivery and pick-up services are good because fewer people are involved. Just keep washing your hands whenever your relatively closed system gets breached.
What if you’re in a situation where you can’t wash your hands? That’s why hand sanitizers were invented. They’re not more effective than rubbing your hands with soap and water. They’re a portable substitute that might be quickly available when plumbing isn’t.
While all ages are vulnerable to the coronavirus, the risk of a severe disease increases exponentially with age. Remember exponential curves from your high school math classes? They’re not straight lines. They suddenly curve steeply upwards. This sharp upward turn in severe disease risk happens at about age 60, and the risk is far worse at 80, likely because older people tend to have more underlying health conditions. The spread of the virus in communities is also exponential. Time and again in multiple localities, the number of infected people has increased slowly at first and then suddenly ballooned. The more infected people there are, the more likely you are to come in contact with them, especially since some have mild or not-apparent infections.
So remember the numbers game, wash your hands and keep your distance. Putting knowledge into practice helps us all.
Linda Eissenberg, Ph.D., is a scientist at Washington University School of Medicine who spent more than two decades studying microbial pathogens. She now works in oncology as an assistant professor of internal medicine.