Colds, Flu, and Cold Noses

Winter is a respiratory infection jungle in my home. Is it the cold that gives us the cold? What can we do besides moving to a warm climate?

The chilly temperatures do not cause colds, but they may inhibit our body’s ability to fight off viruses and facilitate virus survival on hands and surfaces. Lower temperatures and humidity levels in winter aid the survival and transport of virus-laden aerosols and droplets generated by infected individuals. Many viruses survive longest when the relative humidity falls below about 40 percent, while drier air can damage some airway-lining cells, leaving microcracks in our protective barrier, which viruses can exploit.

Moreover, winter’s shorter days (less sunlight) reduce our potential vitamin D production and impair our immune defenses. Huddling indoors to warm up close to potentially already-infected persons further increases our infection risk. However, it was only last summer that researchers uncovered the biological mechanisms involved in the “winter cold” situation.

Cells in the nose are studded with sensor proteins that detect viruses. When these proteins are activated by viruses, they signal the cell to release a swarm of tiny mucous bubbles called extracellular vesicles (EVs). The viruses attach to EVs via their receptors instead of attaching to the nasal mucosal cells themselves. The EVs serve as decoys! Moreover, the EVs chemically neutralize the attached viral invaders and trigger a cascade of other antiviral responses. The vesicle-trapped viruses and those deactivated by the immune responses in the mucus layer of the nasal cavity form a slimy nasal secretion—or “snot”—which we then eliminate.

So here is the new discovery: cold exposure (in the nose) decreases both the total amount of EVs and their attractiveness to the invading viruses. This leaves a greater number of “free viruses” available to directly attach to the nasal mucosal cells and cause a respiratory infection.

Our advice? Keep the nose (nasal passages) warm! This can be done by using a hood that extends far over the face, a scarf that loosely covers the nose and mouth, or a mask that covers the nose and mouth. In each of the cases, the warmth of the exhaled, moist breath helps maintain a beneficial nasal inhalation temperature and humidity. Also, there is some degree of physical barrier protection when scarves and masks are donned. So moms and grandmas were onto something when they told us to “use a scarf around your neck, mouth, and nose” when it’s cold outside. And despite objections, the mask is a useful tool. This is much easier than moving to a warmer climate!