This was first written earlier in summer 2022…
Public Health Ontario has a new report out:
https://www.publichealthontario.ca/-/media/Documents/nCoV/voc/2022/07/evidence-brief-ba4-ba5-risk-assessment-jul-8.pdf?sc_lang=en (PDF)
Key points from it (with some bold and italic from me):
Evidence continues to show that BA.4 and BA.5 are highly transmissible, at least in part due to neutralizing antibody titers against BA.4 and BA.5 being reduced as compared to other variants. BA.4/5 could lead to high levels of community transmission in the absence of public health measures.
For previous sub-lineages of Omicron, a complete primary series and for those eligible, the recommended booster dose(s), provide optimal protection against severe outcomes.
Evidence shows that SARS-CoV-2 reinfection adds risk of all-cause mortality, hospitalization and adverse health outcomes during acute and post-acute SARS-CoV-2 reinfection, and that the risk and burden may increase in a graded manner according to the number of infections. The evidence that SARS-CoV-2 can cause immune dysregulation is increasing. Reducing the risk of SARS-CoV-2 infection and reinfection could reduce overall burden of death and disease in Ontario during the pandemic
Ontario Science Table report
and longer-term.
Text in bold is saying: If you’ve already COVID, and you get infected again, you are at higher risk of bad outcomes than you were the first time. And that quite possibly, the third infection will be riskier than the second infection, and so on.
Text in italic is saying: Evidence increasingly suggests that COVID infection damages your immune system. Meaning: Anyone who’s had COVID might be a bit more immunocompromised than they were previously.
To minimize morbidity and mortality in Ontario, as well as societal disruption, current public health efforts could be augmented in response to the increasing epidemiological trends. Based on evidence of significant immune evasion by BA.4/5 and waning immunity following vaccination, use of public health measures will be the most effective way to reduce the risk of SARS-CoV-2 transmission, and includes: wearing a well-fitted high quality mask whenever feasible in indoor spaces, crowded places (including outdoors) and close contact settings (e.g., public transit), staying home when sick or with symptoms of COVID-19, optimizing ventilation, and use of outdoor spaces.
Ontario Science Table report
I think everyone knows about masks, isolating when sick, and doing stuff outdoors when possible, so I’d like to provide more information about optimizing ventilation.
How does ventilation help?
People already infected with COVID exhale the virus when they breathe, speak, sing, cough, or sneeze. If people not yet infected inhale enough of that exhaled virus, they get infected as well.
Outdoors is safer than indoors because that exhaled virus has lots of “air space” to get diluted in, decreasing the odds of anyone else inhaling enough virus particles to get infected.
Indoors, ventilation essentially exchanges indoor air for outdoor air, so expelling the potentially “high virus” indoor air and replacing it with diluted outdoor air. This is how it’s beneficial in reducing disease spread.
How can you tell if an indoor space is well-ventilated?
If there are windows wide open all around the indoor space, it is well-ventilated. This is a diminishing return: if windows are open on only one side, or are only partly open, that doesn’t increase ventilation as much. But any window opening is helpful. (I can get my house from Fair to Excellent ventilation levels
in an hour or two with open windows.)
As well, window-less spaces can be very well-ventilated through mechanical systems. Problem is, there is no way to tell by looking (or smelling) if an indoor space has good mechanical ventilation. Still, there are some ways you might be able to find out.
Visit, live in, or move to a country where CO2 levels are displayed in public
Belgium will soon be such a country, for example: Belgium agrees on ‘ventilation plan’ for public places – CO2 meters essential.
Japan is another.
And per Covid-19: Canada outperformed comparable nations in pandemic response, study reports:
Japan was an extreme outlier, with by far the fewest deaths and infections despite having the oldest population and imposing the mildest restrictions.
Owen Dyer, The BMJ
Some establishments report it even in places where it’s not required
Apricot Tree Cafe in Toronto, for example, has made clean indoor air part of their brand, having gone to considerable lengths to provide the best indoor air possible. (They also report zero workplace COVID infections, despite restaurants being one of the riskiest workplaces.)
Full Circle Foods in Kitchener has also invested in filtration to improve the air (as I heard on CBC Radio).
Other places might have some useful information buried on a “COVID protocols” page of their website. For example, Centre in the Square says “Ventilation systems have been set to maximize the amount of air exchanges in the building.” (It’s impossible to know if that maximum is sufficient; however, I did measure their CO2 levels at one concert I was at, and they were good.)
An app for that
The Raven CleanAir web app allows you look up various businesses to see what their reported CO2 levels are, and whether they are making any other efforts to clean the air, such as staff masking or deploying HEPA filters. (I am one of the contributors of data.)
Measure it yourself
Unfortunately, there’s no tool for detecting COVID virus in the air. But what always gets exhaled along with viruses is CO2 (carbon dioxide)—and that, you can measure.
Outdoors, the best ventilated spaces we have, CO2 levels are between 400 and 420 ppm.
Indoors, the levels will always be higher than that, but the better the ventilation, the closer you can get to outdoors. This is a typical chart of what the measurements indicate (borrowed from Toronto Public Library), using some of my actual measurements.
| Space | Reading | Assessment |
| Office | 437 to 461 | Excellent |
| Sobey’s grocery store | 612 to 659 | Good |
| Princess Twin Cinema | 700 to 950 | Fair |
| Hair salon | 1008 to 1323 | Poor |
A note about filtration
Some indoor spaces are difficult to ventilate—like airplane cabins. So for those, the air can be “filtered” using HEPA filters and other “scrubbers”. These remove particles from the air, like dust and viruses (if using the correct filter)—but do not remove CO2.
Meaning, a space can have a fairly high CO2 level, but still have relatively clean air due to filtering. Airplane cabins, again, typically measure 1000 to 2000 CO2 ppm when in flight, which is “poor” in terms of ventilation, but are still considered to have relatively clean air because of the extensive filtering they do.
(Another example: My dentist’s office measured over 800, but I wasn’t overly concerned, given the staff being in N95 masks and face shields and the huge HEPA units they had running in all the rooms and in the waiting area.)
What if I’m in a poorly ventilated space?
So if your CO2 monitor is indicating trouble, what to do?
If you can control the space, or can contact someone who controls the space:
- Open windows
- Open doors
- Run bathroom or kitchen exhaust fans
- Move some people to another room
- Make sure the ventilation system is running
- Make sure the ventilation system fan is set to Continuous, not On-demand
- Run a HEPA filter (sized for the room) or a Corsi-Rosenthal box
- In a car, taxi, or Uber, ensure that the fan is set to bring in outdoor air, not just re-circulate the car air
If you can’t control the space:
- Mask up, ideally with an N95 or better
- Distance from others as much as possible
- Shorten your stay as much as you can
- Try one of those portable HEPA units
Bonus: Improving indoor not only helps prevent transmission of Covid, but all other airborne illnesses (flu, colds, tuberculosis, measles, monkeypox…), and can reduce incidence of fatigue, headache, allergies, and irritated sinuses. It also improves cognitive performance.
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