COVID-19 Outdoor Transmission Risk is Low
Idiots wearing masks outside

COVID-19: What Are The Outdoor Transmission Risks?

Overview

Ah, summer! The perfect time to enjoy relaxing at the lake, taking a trip to a National Park, or enjoying yourself at an amusement park. Except in 2020 when the media and twitter-pundits are too busy telling everyone they should be scared and there’s no conceivable reason to go outside1.

Yes, much is still unknown about COVID-19 but it is likely that outdoor transmission risks are minimal. And some studies are starting to filter out showing exactly that. After all, keeping yourself physically and mentally healthy is the one of the best ways to keep yourself from getting sick and being outside is one of the best ways to do that. In fact, according to this study from Canada’s National Collaborating Centre for Environmental Healthy “research looking at healthcare workers, travelers on air planes, and the household contacts of tens of thousands of COVID-19 cases has consistently shown that transmission is strongly dependent on being in close proximity to a sick person for some period of time.

And, of course, you won’t be in close proximity to a sick person for some period time if you’re outside2. Incidentally3 , that’s why public-wide “lockdowns” are completely the wrong strategy. Because once a person does get sick, they quarantine themselves in close proximity for an extended amount of time next to family and friends and get them sick too. Only in a society where there’s absolutely no contact with others would a lockdown strategy truly work to stop the spread of the disease. But, of course, then you’re no longer a “society” — you’re a vassal of the State and no longer have any rights.

So, not only do lockdowns cause mental harm and stress but they also cause physical harm by preventing sunlight and fresh air from reaching your body. Most people find it easier to exercise outside their home – going outdoors (walking, running, etc.) or going to a gym. Obviously, forced closures of parks, gyms, pools, and the like prevent some level of exercise and increase social isolation. Conversely, having those places closed actually increases some risks as people look to other less safe options for entertainment and social interaction. Logically, allowing and enabling people to spread out as much as possible in outdoor spaces will reduce the risk of disease transmission.

It is now generally believed that the mode of transmission is via aerosols – and the viral load outside in the fresh air would certainly be lower than inside given the same factors. Additionally, it is very well known that higher temperature and humidity inhibit viral reproduction, even for COVID-19. Being in controlled environment with lower temperature and humidity could conceivably allow the virus to spread. Temperate and humidity are a large factor as to why flu-like illnesses are seasonal. And sunlight itself rapidly inactivates and quickly kills viruses. Additionally, there is no evidence filtering out that Vitamin D – which is actually a hormone your body makes when exposed to the sun – provides benefit against COVID-19. So, it makes complete sense to be outside – in the higher heat, humidity, sunshine, and open spaces – whenever tolerable.

And even being in the water is very safe. Although scientists don’t have data on COVID-19 specifically, other coronaviruses are not stable in water and are very sensitive to chlorine. So, going to the ocean, lake, or pool is actually a great way to de-stress and exercise while still not exposing yourself to undue risk.


Outdoor Transmission Risk Study

With that said, here’s an interesting study out of China that bears out what I explained above: that indoor transmission is the main mode of COVID-19 transmission and that outdoor transmission risk is low(er). According to the study, they tracked 1,245 confirmed cases and they found that being in an indoor shared space is the major infection risk. Only 1 outbreak, involving 2 cases, happened in an outdoor environment. That’s .1% of the cases that were tracked. Yes, .1%. The full study is linked in the reference section. If you don’t wan to read the full thing, the results and conclusions pasted below.

Results: Three hundred and eighteen outbreaks with three or more cases were identified,
involving 1245 confirmed cases in 120 prefectural cities. We divided the venues in which the
outbreaks occurred into six categories: homes, transport, food, entertainment, shopping, and
miscellaneous. Among the identified outbreaks, 53·8% involved three cases, 26·4% involved
four cases, and only 1·6% involved ten or more cases. Home outbreaks were the dominant
category (254 of 318 outbreaks; 79·9%), followed by transport (108; 34·0%; note that many
outbreaks involved more than one venue category). Most home outbreaks involved three to
five cases. We identified only a single outbreak in an outdoor environment, which involved
two cases.

Conclusions: All identified outbreaks of three or more cases occurred in an indoor
environment, which confirms that sharing indoor space is a major SARS-CoV-2 infection
risk.

Reference List:

"Indoor transmission of SARS-CoV-2" https://www.medrxiv.org/content/10.1101/2020.04.04.20053058v1.full.pdf
"COVID-19 and outdoor safety: Considerations for use of outdoor recreational spaces" 
https://ncceh.ca/sites/default/files/COVID-19%20Outdoor%20Safety%20-%20April%2016%202020.pdf
"Airborne SARS-CoV-2 is Rapidly Inactivated by Simulated Sunlight" https://academic.oup.com/jid/article/doi/10.1093/infdis/jiaa334/5856149
"Temperature, Humidity, and Latitude Analysis to Estimate Potential Spread and Seasonality of Coronavirus Disease 2019 (COVID-19)"  https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2767010

  1. other than to delivery their groceries or deliver their packages, of course []
  2. protests not withstanding []
  3. or not, depending on your world view []