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Winter Conditions May Affect Coronavirus Spread

A discussion of a recent CBC article regarding winter conditions on coronavirus transmission, and how these conditions affect climbing

Though the ethics of climbing outdoors remain unclear, a recent interview with professor Michael Brauer from the University of British Columbia’s School of Population and Public Health has shed light on some of the more technical questions relating to outdoor conditions and COVID transmission.

The original CBC article by Michelle Ghoussoub can be found here, though today we will discuss what the article says and its relationship with rock climbing. To begin, transmission.

Though there has been concern about COVID transmission through surfaces, the dominant form of communication is air-borne. The SARS-CoV2 coronavirus that causes the COVID-19 disease is primarily transferred through respiratory droplets resulting from exhalation. Like many respiratory viruses, this virus spreads more easily in the winter.

Why does this virus spread more easily in the winter? The primary reason is that people spend more time interacting in poorly ventilated indoor spaces when it is cold outside. However, it is possible that winter conditions might increase the spread of the virus outdoors. This is due to condensation.

How does condensation present? It is the cloud a person breathes out in the cold, winter air. This cloud forms as a result of warm water vapour coming into contact with colder, drier air. The vapour condenses into water droplets making for a visible cloud. This process is continuous in the winter and rare in the summer.

Due to the fact that breath is saturated water, if a person carries the coronavirus, asymptomatically or otherwise, their exhalations carry the coronavirus as well. Masks block these droplets from entering the air making them an essential tool for the outdoor recreationalist.

Though winter’s breath may appear to be gaseous, it is a physical spray of condensed water vapour. This condensation creates water droplets that contain the virus if the individual is infected. Breathing in another’s breath, especially when it has become condensed into a more physical form, allows for easy communication of the virus.

To that effect, humidity can magnify these conditions.

As discussed in our conditions piece, lower humidity tends to be better for climbers as it means that there is less moisture in the air. Though dry air makes it is easier to stick to rock, it also means that the water droplets a person exhales are smaller than air were more humid. When water droplets become smaller, they hang around in the air for a longer amount of time.

When the humidity is higher, the droplets become larger and fall to the earth faster. This inhibits viral transmission and suggests that the summer months might be less dangerous for communication given the same interaction.

In the summer, there is greater evaporation and evapotranspiration in effect due to the conventionally warmer and sunnier conditions. This increases the humidity to levels significantly higher than in the winter. Any person that follows conditions for climbing in Ontario will notice around a 20% difference in average humidity between the winter and summer months.

With all of this said, Peter Juni, an epidemiologist at the University of Toronto, says that most of the conversations regarding conditions and their effects on transmission are largely hypothetical.

He says that because humidity levels are relative to temperature, they stay fairly consistent from summer to winter. The biggest reason for transmission increase in the winter is that people spend more time interacting indoors.

Juni said, “If the air is less humid, these particles stay longer airborne and this is a problem inside because you don’t have good ventilation. However, outside what happens is any potential viral particles that are dissolved into aerosols, they get literally blown away.”

Should a person be discouraged from exercising outdoors? It depends. Brauer said, “Certainly, activities where you’re close to people — that’s where you need to be concerned. Skiing itself wouldn’t be a particular concern but waiting in line might be.”

How does this apply to climbing? It is difficult to say. Though climbing can be done alone or at least distanced from other athletes, climbers tend to exist in the same areas at the same times. If humidity and temperature do play a role in transmission, then the winter is more dangerous, in terms of transmission, than the summer for climbing.

Last week, two climbers (who asked not to be named) in the Canadian Rockies were climbing in the same mixed climbing cave, were later diagnosed with COVID-19. The two followed every health guideline, stayed within their family bubbles and only unmasked when climbing at the cave. While they might have contracted the virus elsewhere, there’s a chance they got COVID-19 while climbing.

The bigger concern, realistically, is that which happens to your local health care system when ICU-level injuries occur. These put additional stress on health care systems already working to fight a pandemic.

Though pandemic fatigue begins to weigh, it is important that we each do what we can to fight for public health.