Wrap Up warm: the Cold Virus Replicates Better at Cooler Temperatures

Your mother may have been right when she reminded you to don your hat and scarf before heading into the cold. A Yale-led study has found that the most frequent cause of the common cold, rhinovirus, can reproduced more efficiently in the cooler temperature of the nose than the warmer lungs.

Though it has long been known that rhinovirus replicates more easily in the somewhat cooler environment of the nose than at core body temperature, this study is unique in that it considers how temperature effects the functioning of the immune system, rather than the virus itself.

Akiko Iwasaki, a Yale professor of immunobiology, led the study, which examined cells taken from the airways of mice. When comparing the immune response to rhinovirus in cells incubated at 37 degrees Celsius and those incubated at the slightly cooler 33 degrees Celsius, the innate immune response was found to be impaired at the lower temperature.

This strongly suggests that the change in temperature affects the immune response rather than the virus itself. Supporting this conclusion was the finding that in immune deficient mice, the virus was able to replicate at higher temperatures.

Iwaskai explained that this means “it’s not just virus intrinsic, but it’s the host’s response that’s the major contributor”.

Around 20 per cent of people harbour rhinovirus in our noses at any time. However, far from simply sparing us from the inconvenience of a runny nose, the research has important implications into how temperature affects the immune response to other conditions. In children with asthma, the cold can cause severe breathing problems. Future studies might investigate the immune response to rhinovirus-induced asthma.