Why should we care?

Airborne illnesses like influenza & COVID-19 have surged in recent years, straining medical facilities and causing billions of dollars of economic losses. In 2026, influenza cases in the United States hit a 25-year high. In 2025, 7% of the UK workforce was absent due to long-term sickness, causing a £130bn drop in economic output. That same year, sick leave levels in Germany hit an all-time record. These infections are the primary cause of pneumonia, which is a leading cause of child mortality and was the sixth largest cause of death in Canada in 2024.

What can we do?

These infections mostly spread via small, exhaled droplets (aerosols) that linger in the air and get inhaled by others. They're most common in crowded indoor spaces. While vaccines help reduce severe outcomes of infections, their ability to prevent infection is very limited. The best protection is a good mask (like an N95), which drastically lowers the inhalation and exhalation of infectious aerosols. We can also reduce infections by improving indoor air quality. That means increasing ventilation and adding HEPA purifiers to more rooms. Once indoor air quality seriously improves, masking will be largely unneeded in non-medical areas.

What about natural immunity?

Some microorganisms can benefit our immune system, like harmless outdoor bacteria and other microbes that live in dirt. They have been with us for all of human history. In contrast, influenza and other airborne infections have only been with us for ~4% of our evolution, when the agricultural revolution allowed humans to live in crowded, permanent settlements. These infections are not essential for immune system development; early childhood infections don't reduce the odds of developing immune system issues (like allergic diseases). Instead, they damage the body.

In children, they increase mortality risk and significantly raise the odds of developing inflammatory heart disease, autoimmune diseases, diabetes, and chronic kidney disease. In adults, these infections also greatly increase mortality risk and raise the odds of experiencing lung conditions, strokes, diabetes, and reduced brain connectivity.