Crowds and Respiratory Infections

Respiratory infections are the leading reason for hospitalizations worldwide, and such infections are more common during the winter than summer months. Why is this?

Various types of “germs” can cause respiratory infections. The germs that typically do so are bacteria, fungi, and viruses. We breathe in germs with every breath we take, since the air is full of them. But most people would never know that, especially since the germs in air are too small to be seen using “naked” eyes. And though the air is full of germs, we should only worry about the ones that harm us. For example, the air contains germs that only affect plants, or animals, and so on, and most of those don’t affect humans.

Respiratory infections vary in severity, and there are many reasons for that, including the type of germ and the overall health of the person who breathes them. Many of the cold-weather-associated respiratory illnesses are caused by viruses. For example, common colds are typically on the milder scale of illnesses, and are caused by various viruses. More severe respiratory infections may also be caused by viruses, such as those that cause influenza and cOVID-19.

It was once thought that cold weather itself made people get respiratory infections. But one only has to think about residents of cold places such as Alaska; if cold weather made people sick, there would be few people who would survive in cold locales. This is not the case at all.

So why are there more respiratory infections during winter months? The real driver is crowding of people into confined places. Any time there are mass gatherings, respiratory infections are a typical outcome. When there are big music festivals, when university classrooms get packed during the first days of the school year, and so on, respiratory infections occur in those in attendance. Why?

All humans posses a microbiome, meaning we are all carriers of germs. And our microbiomes are unique to the person. When we exhale, cough, speak, sing, etc., we release germs into the air. It should not be a surprise, then, that people who live in different places, release different germs. This means that in the case of respiratory germs, that many people in a given community may have been exposed to some germ, developed an illness, then recovered, but still harbor the germ and can spread it to others. Thus, when people from different cities, countries, states, etc. come together for a music festival or other mass-gathering event, the risk to all of getting exposed to new germs is high.

In confined areas, such as a crowded bar, the air within a room may not circulate freely, and the air can be full of harmful germs. This does not have to be only during winter months. During warmer months, many people crowd into air-conditioned habitats. And now that international travel is common, this means that in tourist destinations, people from the Northern and Southern hemispheres can be within the same confined space, exemplified by what might happen in tourist attractions. This can be problematic because the seasons are opposite in the Northern and Southern hemispheres, and thus respiratory infection time associated with cold weather may be occurring in one hemisphere but not in the other warmer hemisphere.

Viruses in particular are very small, and depending on conditions, can remain adrift in air for relatively long periods. Air conditioning favors the length of time they stay in the air. In general, hot and humid conditions make particles suspended in the air fall to the ground faster than they normally would in air-conditioned spaces. One reason is that particles in the air get covered by water vapor, which makes them heavy, and they fall to the floor. Air conditioning partly works by removing excess water vapor from the air. This creates favorable conditions for airborne particles to remain free-floating. The cooler temperatures also benefit may germs; heat tends to kill many germs whereas cooler temperatures help them survive in the air.

So to better one’s chances of not getting a respiratory infection when it gets cold, a good idea is to stay away from mass gatherings. And one has to use common sense. The closer you get to an “emitting source” (a sick person or germ carrier who is releasing respiratory pathogens in their sneezes, coughs, or even while singing or speaking), the higher your risk of inhaling a germ that may cause illness. No sense sticking close to a stranger who is coughing or sneezing.

What else can someone do? An effective air cleaner that removes airborne germs can greatly reduce inhalation exposure risks when one must be in spaces occupied by many people. Not all air cleaners work well, and many fail to trap virus particles. Cleaerosol’s prePaer air cleaning units are a shining example of air cleaners that are up to the job. Virus particles are much smaller than bacteria and fungi. prePaer units effectively trap not only big particles, but also, virus particles. In a study to be presented elsewhere, prePaer units trapped SARS-CoV-2 (the virus that causes COVID-19) and other viruses.

Stay healthy!