Although a person is 4x more likely to catch a cold in the more frigid months of the year, cold viruses are in the environment 24/7, seven days a week, 365 days a year. The common cold never takes a holiday, although it may end up crashing yours.
Why Are Colds More Common in Winter?
The common cold can be caused by any one of hundreds of different viruses. That’s why there is no vaccine. Some of these viruses spread best through contact, others through aerosolized droplets that are launched via coughs and sneezes.
In the warm and humid summer months, it is harder for airborne illnesses to spread, since water droplets from humid air are attracted to small particles, such as tiny viruses, weighing them down, and ultimately grounding them. The influenza virus, an airborne virus, is covered with a lipid envelope that does a better job of protecting the virus in chilly, rather than warm temperatures. This is why influenza is a winter illness.
The common cold, although it can be spread through the air, is more often transmitted through touch. People are also more often in close, indoor contact during colder months, making it easier to spread germs both by air and by touch.
Why Do Colds Happen in the Summer Too?
Summer colds do still occur, and they can be even more tenacious and miserable than winter colds. The recirculated air in air conditioned environments dries out nasal passages, where cold viruses thrive, making it easier for them to infect the cells of the nasal mucous membrane.
On sweltering days, people flock to air conditioned environments. The workplace is one example, where many people repeatedly touch the same objects—doorknobs, keyboards, staplers—leaving behind viral particles. And sweltering summer days are when parents often opt to take their cabin-fevered children to indoor play areas, all full of surfaces being touched by many tiny hands.
Traveling and the Common Cold
Airplanes, stuffed with business travelers and vacationers, are the perfect enclosed space for sharing germs. The air is recirculated during flight, making airborne illnesses a danger, and with planes often departing again immediately after arriving, it is unlikely that many of the surfaces on the plane cleaned between flights.
Also, when people travel to different geographic areas, they may encounter germs that are local, or endemic—such as versions of the common cold that they may not have ever been exposed to before and that their immune system has no experience battling.
How to Prevent a Summer Cold
Some tips for avoiding summer colds:
- One of the easiest and best defenses against many types of infectious disease is thorough and frequent hand washing.
- Keep hand sanitizers handy for when soap and water isn't available for hand washing.
- Use disinfectant wipes to clean frequently-touched surfaces in the home, such as door knobs, handles, and light switches.
- When the weather is nice, spend time outdoors enjoying summer!
For more information on microbiology, see the Virtual Microbiology Classroom of the science education website Science Prof Online.
Sources
Bauman, R. (2012) Microbiology: With Diseases by Body System. Benjamin Cummings.
Cardiff University (2011) Summer Colds.
Mayo Clinic (2011) Common Cold.
NIH News (2008) NIH Scientists Offer Explanation for Winter Flu Season
Stability of Virus' Membrane at Cold Temperatures May Ease Winter Spread.
Salamon, M (6/15/2011) Extra insult: Colds in summer nastier, last longer. MSNBC
Tami Port - Tami Port is a college professor of cell and microbiology and creator of ScienceProfOnline.com, a free science education website.
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