Mallika Venkatramani discusses the real reasons behind the popular belief about falling sick in the cold season.
“It’s very cold outside, dear. Don’t go out or you’ll fall sick.”
Most of us have heard something along these lines. Such pieces of well-meaning advice have been reiterated from parent to child down the generations. However, if the 21st century is an age of breakthrough and we are beginning to develop a penchant for questioning household beliefs, this rather harmless warning now seems to be an addition to the list of old wives’ tales.
“Boosted activity of both types of viruses is the first factor causing sickness.”
It is believed that winters and being ill are intertwined, because so many people get sick as soon as temperatures start dropping. However, it has been well-established for some time now that the common cold is transmitted not by low temperatures, but by a group of retroviruses called rhinoviruses. Rhinoviruses generally thrive in the nasal cavity, which is around 2°C cooler than the chest cavity. Scientists at Yale University have discovered that the intensity of immune action directed at the lung cavity is higher than that heading for the cooler nasal regions. This is a bonus for rhinoviruses, which are able to thrive in the nasal passage further cooled by wintry weather, triggering the common cold.
We become blue with the flu due to influenza viruses. Influenza viruses get more active and last longer in winter. According to a study conducted by the National Institutes of Health in the USA, their viral coats are made of lipids which solidify as temperatures reach freezing point. This enables these viruses to resist freezing temperatures better, aiding their person-to-person transmission. As they enter an individual’s chest cavity where the internal body temperature is warmer, the coating melts and the viruses invade host cells, making the individual sick with the flu.
“Rhinoviruses generally thrive in the nasal cavity, which is around 2°C cooler than the chest cavity.”
Thus, it is not the cold temperature per se that affects us, as common advice would suggest. Boosted activity of both types of viruses is the first factor causing sickness. The second important factor is that, in the cold, we are more likely to stay home to keep warm, increasing our interactions with those around us, giving these viruses a chance to be better circulated amongst those close to us. Coughing and sneezing in close proximity causes the virus-laden aerosol droplets from an affected individual to travel to another person more easily. Finally, we tend to decrease ventilation to shield our homes from those icy blasts, further allowing the viruses to propagate in our sealed-up homes.