Is there a connection?
Does cold weather make you sick? For centuries, this myth has led grandmothers to insist that kids sit away from drafts, keep a hat on in cold weather, and avoid going outside with wet hair.
But if this is a myth, why do colds and the flu peak in the winter? The answers are complex and fascinating.
In terms of infectious illnesses, germs make you sick, not cold weather itself. You have to come in contact with rhinoviruses to catch a cold. And you need to be infected with influenza viruses to contract the flu.
Rhinoviruses peak in spring and fall, and influenza viruses peak in winter.
While the cold can’t be the only reason, there is a connection between being chilled and getting sick: cold air may contribute to conditions that lead to illness.
Viruses and the immune system
Some viruses are actually more likely to spread during cold weather. Rhinovirus (the cause of the common cold) replicates better at cooler temperatures, such as those found in the nose (33° to 35° Celsius) compared to the body core temperature (33° to 37° Celsius).
However, one study found that immune system cells initiate a more robust antiviral defense at lung temperature versus nasal cavity temperature. This might mean that the body may not fight the virus as well if the temperature in the nose and upper airway is lowered by environmental cold.
Some studies assert that influenza virus is most stable in cool, dry temperatures. However, other studies show that the disease is also prevalent in humid, warm climates. Other factors suggested as potentially affecting immune response include sudden changes in temperature or the impact of dark and light cycles.
But the bottom line is that cold doesn’t cause illness, although weather or other factors may weaken your ability to fight off illness.
Cold air forces you inside where it’s warm. Dry air associated with central heating makes it easy for cold and flu viruses to get into your dry nasal passages.
But thoughts on whether this theory is correct are divided.
Humidity and ventilation
Dry indoor air itself doesn’t get you sick. But it may play a role in letting aerosol droplets from a sneeze survive and prosper.
Researchers at Tianjin University in China found that students in dorm rooms with poor ventilation caught more colds.
Additionally, researchers at Virginia Tech found that good ventilation, as well as high relative humidity indoors, renders the influenza A virus inactive.
Dry air outdoors, as measured by absolute humidity, may also be linked to flu outbreaks. According to the National Institutes of Health (NIH), dry winter air allows the flu virus to survive and transmit itself.
Additional NIH research suggests that the coating of a flu virus becomes tougher at temperatures close to freezing, making them more active, more resilient, and easier to transmit in the winter.
More clues to why you’re sniffling
It’s likely that being outside in cold weather inhibits the ability of mucus and nasal hairs to work disease agents out of your nose.
It’s also likely that when you get back inside in a room with the windows shut and people sniffling, you are more likely to be exposed to germs.
As people return to college, school, work, and day care in the fall, viruses find ideal conditions to hop from one host to another, before cold weather even sets in.
Culled from Healthline