Are Chilly Temperatures The Cold Culprit?

May 30, 2013 | Steven Purcell | Research & Policy

As it turns out, mother really does know best. For those of us who can remember being told countless times to ‘bundle up’ against the chill of winter, only to neglect that hat or button up our coat, we may have more than mother’s wisdom to connect the scarf to the sniffles. For those of you who may not have heeded her advice and wound up with a cold, there’s a reason, and scientists at Yale University may know why.

The culprits for the common cold most often are rhinoviruses. Although there are many viruses out there to make us ill, our environment is teeming with rhinoviruses, which account for the majority of the 1 billion plus cases of the common cold in the United States each year. The virus is spread through airways, close personal contact, or by handling infected objects and then touching your eyes, mouth, or nose. For most people, symptoms involve a sore throat, runny nose, and perhaps coughing and sneezing as the virus progresses.

We’ve all experienced this typical ailment. For most, recovery comes in a week or two, with lots of fluids and rest. Many choose to augment their recovery with vitamin C or with other over the counter supplements or medication. We’re also taught to cover our mouths when we cough or sneeze, wash our hands with soap and water, and avoid contact with those who are sick. Despite our best efforts, ‘cold season’ can sometimes get the best of us. It tends to go without saying that wintry weather can bring the common cold. However, there hasn’t really been a lot of scientific evidence to prove the link between cold temperatures and susceptibility to colds until recently.

Researchers found a mechanism by which a rhinovirus that acts in humans is able to proliferate more easily in cold versus warm temperatures. Results of the experiment carried out at Yale University were presented by Dr. Ellen Foxman May 19 at the conference for the American Society for Microbiology.

Beginning with mice susceptible to a mouse-specific rhinovirus, researchers at Yale were able to observe a natural immune response that was stronger in warm conditions. Specifically, more antiviral immune signals are sent out to bolster the immune system in warm conditions. When it was colder, there were less signals and the mouse was thus less able to fight off the infection. Next, the researchers grew human airway cells, whose temperature are influenced by the air we breathe, and infected them with a human rhinovirus analogous to the one used in mice. The warm cells in this case were more likely to undergo programmed cell death (PCD), which is a natural immune system defense mechanism that terminates cells to prevent the spread of the rhinovirus. The findings suggested that the rhinovirus was more successful at infecting the host under cooler conditions. Foxman noted that breathing cool air is enough to ‘chill’ the upper respiratory system just enough to allow infections to ‘flourish’.

It is important to note that this is no smoking gun. While it may be the case that cold air allows opportunistic infections to take advantage of a host’s compromised airways, the pathway from infection to recovery is complex. Although there are many factors that lead to the common cold and as many yet undiscovered, we can now be a little more certain that mother knows best. You might just want to tie your scarf a little tighter the next time you’re exposed to the cold. 

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