Air

The air you breathe will make you sick … if you’re near a sniffler and sneezer

Your co-worker is coughing and sneezing in the cubicle just down the way. The sniffling and throat-clearing make it difficult to concentrate. You are worried about getting sick yourself, but the etiquette of asking someone to go home or to stay in bed is tricky to navigate. Some of your colleagues are ready to march the snot-nosed sicko out the door, but you wonder just how much of a problem it really is to breathe the same air. You use your hand sanitizer, try to avoid being within sneezing range of their red nose, and you definitely are not shaking hands—but are you still at risk of catching their cold?

Unfortunately, the answer to this one is “maybe.” Sometimes, breathing the same air as a sick person will make you sick. The viruses that most often cause colds in humans are called rhinoviruses. For a long time, it looked like the main way that rhinoviruses were passed from one human being to another was through direct contact. The rhinoviruses most often passed from one person to another by directly touching things that had been contaminated by coughing and sneezing. This is why hand-washing is so important. Your hands typically touch contaminated objects, and when you put your hands in your mouth or nose, the virus creeps in to infect you. A sick person’s hands are also a big culprit of passing on cold viruses. Coughing and sneezing into your hands covers them with tiny (or, sometimes, not so tiny) droplets of mucus that contain the cold virus. When you touch things with your contaminated hands, you leave behind infectious mucus that can get other people sick. Washing hands and avoiding contact with a sick person’s contaminated hands or the things their hands may have touched are still the most important ways to avoid catching another person’s cold.

If cold viruses were only passed from person to person by direct contact, then you would not have to worry much about breathing the same air. You could just wash your hands and keep a little distance, and you would be fine. However, more recent studies have shown that some cold viruses are aerosolized. This means that the virus is sent into the air in small droplets of fluid that come spewing out of your mouth or nose when you cough or sneeze. With this kind of transmission, you’re most at risk if you are very close to that coughing or sneezing person. With some bad luck, you might get these virus-containing droplets of fluid into your nose or mouth.

But what about someone who is not within spitting range? Are you in danger just by breathing in the same air? This is where newer studies give us especially bad news. There is evidence that some viruses get aerosolized into the air in a way that allows them to circulate through buildings, and even to infect people who are not particularly close by. Many of the buildings in which we spend our time are relatively well sealed. They have central heating, ventilation, and air-conditioning, and the indoor air circulates around the building for some time before it is exchanged for the air outside. In these conditions, it appears that some viruses get circulated in the indoor air and cause infections in other people in the building.

It is much more likely that you will be infected by someone near you or by the mucus that someone leaves on your hands or on your phone, but there is a chance that you might get sick from someone on another floor too. Good ventilation systems can do a lot to prevent the spread of sickness through the air. If the system frequently exchanges indoor air for outdoor air, it can prevent most of these infections that spread through the air.

These studies are looking at colds or upper respiratory infections caused by viruses, and not at other types of sicknesses. Many other forms of illness, such as diarrhea or strep throat or skin infections, are not spread through the air. These illnesses are usually spread by direct contact, and so the air around people with these sicknesses is not going to make you sick. And other illnesses are not contagious at all and cannot be passed from one person to another. For example, you cannot get heart failure, diabetes, or leukemia from another person.

Those of us who work in hospitals and breathe in “sick air” all the time can easily avoid getting sick ourselves. There’s no trick to it. We follow the same recommendations we give you in this book and in Don’t Swallow Your Gum!: wash your hands frequently, get a flu shot, and if you have to be around someone who has a cold or viral respiratory infection, wear a mask or try to give them more personal space.