Jeff Gilchrist Profile picture
Jun 21, 2022 8 tweets 3 min read Read on X
COVID-19: Comic and video explanation of transmission

Multiple years into the pandemic and many still don't understand how the airborne transmission of respiratory viruses like COVID-19 work. 🧵1/
The Aerosol Science Research Center in Taiwan has put together an explainer comic and video for people to more easily understand ( aerosol.nsysu.edu.tw/en/scopes/108 ). 2/
The youtube video can be found here ( ). 3/
Hopefully this will help people understand that being in a closed meeting room of people for multiple hours with people spaced exactly 2m apart is not sufficient to prevent transmission from a virus that travels in the air. 4/
With poor ventilation those virosols (virus-laden aerosols) can remain in the air for hours so you might even get infected by someone who was in the previous meeting and is not even there any more. 5/
Surface cleaning does *not* stop airborne transmission and physical barriers like plexiglass can actually disrupt air flow and trap higher concentrations of aerosols making things worse. 6/
How do you reduce the chance of airborne transmission?
- improve ventilation & air filtration
- wear mask with proper fit (N95 or better)
- avoid clustering
- keep physical distance (2m is not sufficient for aerosols)

7/
"We are exposed to massively more pollutants, toxins, and pathogens via air than food and water." so fixing and improving air quality helps with so much more than just COVID-19 ( ). Image by @akm5376 8/

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More from @jeffgilchrist

Dec 24, 2024
#Variant update for #Ontario, #Canada (to Dec 10, 2024)

The KP.3.1.1 #DeFLuQE variant has finally been surpassed with XEC now in top place above 20% while the other 5 (MC.* and XEC.* descendants) remain < 7%. Graph tools by @Mike_Honey_ 🧵1/ A line graph showing the lineage frequency of the top 7 COVID-19 genomes in Ontario, Canada, up to December 10, 2024. The graph includes data from 4,928 sequenced genomes. The x-axis represents dates from October 27 to December 08, while the y-axis represents lineage frequency percentages from 0% to 35%. Different colored lines represent different genome lineages: KP.3.1.1 (blue), MC.1 (green), MC.13 (purple), MC.16 (pink), MC.24 (orange), XEC (brown), and XEC.8 (yellow). Below the main graph, there is a bar chart showing the number of samples (n) collected each day, ranging from 0 to 200 s...
XEC is a combination of KP.3.3 and KS.1.1 that recombined together. MC.1 is a direct descendant of KP.3.1.1 with one spike mutation at T571I. To learn more about how variant naming works, you can read this article I wrote with @paulseaman31 ( ). 2/docs.google.com/document/d/1q0…
This Sankey graph shows the proportion of variants from PCR test genomic sequencing in Ontario since October 27, 2024. You can follow the lineage backwards to see where a variant is a descendant from. 3/ The Sankey diagram visually displays the evolution and distribution of sequenced genomes in Ontario, Canada, up to December 10, 2024. The diagram uses colored bars and curved lines to show the flow and relationships between different genome variants over time. Each variant is labeled, such as "XEC," "BA.2," "BA.2.86," "JN.1," "KP.3," and various sub-variants. These bars and lines illustrate the transitions and derivations from one variant to another. The total number of sequenced genomes depicted is 4,928. This visualization helps to underst...
Read 16 tweets
Dec 22, 2024
Population rate vs raw numbers

This is a good example of why it is useful to understand the importance of population *rate* and not just look at raw numbers. The first graph shows raw numbers and the second graph population rate. 🧵1/ #ED #Respiratory #Virus #Population #Ottawa Chart of Respiratory Related ED Visits by Week and Age (Ottawa, ON, Canada) with raw numbers
Chart of Respiratory Related ED Visits by Week and Age (Ottawa, ON, Canada) with population rate per 100K
Ottawa Public Health makes only the raw data available for All causes and respiratory-related emergency department visits to Ottawa hospitals by age group and week ( ). 2/open.ottawa.ca/datasets/ottaw…
If I take the data and plot all the ages together, you can at least see all of the age groups at the same time but it is just the raw numbers. 3/
Read 12 tweets
Dec 17, 2024
This is amazing, not only a lower cost CPC for measuring mask fit and ultrafine particles in a room, but also a new probe to measure fit of a respirator without destroying it, check out the video from @OpenAeros and @masknerd to see how it works ( ). 🧵1/ Woman wearing N95 head band respirator inserting new probe design in side of respirator so you don't have to puncture the front, the new OpenAeros OpenCPC machine operating on the table showing the ultrafine particle levels and Aaron Collins (@masknerd) holding the new blue probe against his face to show what it looks like.
@masknerd also demonstrates how you can use OpenCPC to measure how well an air cleaner is filtering particles when you insert the probe into the output vent where particles dropped to 6.4/cm^3 from the regular 700-800/cm^3 for the room. 2/ Aaron Collins (@masknerd) holding the OpenCPC probe inside the fins of a portable air cleaner to measure particle concentration showing it has dropped significantly.
When Aaron Collins moves the probe to a couple of feet in front of the portable air cleaner, levels go back up to 785/cm^3 which is the same as the room concentration indicating this type is filtering the air but doesn't create a "clean bubble" in front of it. 3/ Aaron Collins (@masknerd) holding the OpenCPC probe a couple of feet in front of a portable air cleaner to measure particle concentration, showing it has gone back up to room concentrations.
Read 6 tweets
Nov 10, 2024
COVID-19: Stats, Guides, Articles, Calculators

COVID-19 guides, useful info, stats, calculators & 600+ scientific articles: covid.gilchrist.ca

Ottawa, Canada weekly stats: covid.gilchrist.ca/Ottawa.html

Ontario, Canada weekly stats: covid.gilchrist.ca/Ontario.html

🧵1/ Graph of COVID-19 wastewater levels in Ottawa, Ontario, measured from Sept. 1, 2021. Weekly stats available at ( http://covid.gilchrist.ca/Ottawa.html )
Sankey graph (height of each bar is # of sequences for that variant) showing top variants and their lineages over the past 6 weeks from PCR test genomic sequencing in Ontario, Canada. Visualization tool was created by @Mike_Honey_ ( https://app.powerbi.com/view?r=eyJrIjoiNzE5YzczODItMDQzMS00M2EzLWFjNWYtMjg3OTY3NTNhZDM3IiwidCI6ImRjMWYwNGY1LWMxZTUtNDQyOS1hODEyLTU3OTNiZTQ1YmY5ZCIsImMiOjEwfQ%3D%3D&pageName=ReportSection32240d6b62ba73667e98 )
A sample of some threads listed on the website ( covid.gilchrist.ca ):

How do variant designations work and relate to our immunity ( x.com/jeffgilchrist/… )? 2/
Why should we care about a virus with a "99.8% survival rate" ( )? 3/
Read 16 tweets
Nov 10, 2024
#Variant update for #Ontario, #Canada (to Oct 29, 2024)

The KP.3.1.1 #DeFLuQE variant is having some competition from XEC and MC.1 now. Graph tools by @Mike_Honey_ 🧵1/ Graph of top 7 COVID variants from PCR test genomic sequencing in Ontario, Canada. Visualization tool was created by @Mike_Honey_ ( https://app.powerbi.com/view?r=eyJrIjoiNzE5YzczODItMDQzMS00M2EzLWFjNWYtMjg3OTY3NTNhZDM3IiwidCI6ImRjMWYwNGY1LWMxZTUtNDQyOS1hODEyLTU3OTNiZTQ1YmY5ZCIsImMiOjEwfQ%3D%3D )
XEC is a combination of KP.3.3 and KS.1.1 that recombined together. MC.1 is a direct descendant of KP.3.1.1 with one spike mutation at T571I. To learn more about how variant naming works, you can read this article I wrote with @paulseaman31 ( ). 2/docs.google.com/document/d/1q0…
This Sankey graph shows the proportion of variants from PCR test genomic sequencing in Ontario since September 15, 2024. You can follow the lineage backwards to see where a variant is a descendant from. 3/ Sankey graph (height of each bar is # of sequences for that variant) showing top variants and their lineages over the past 6 weeks from PCR test genomic sequencing in Ontario, Canada. Visualization tool was created by @Mike_Honey_ ( https://app.powerbi.com/view?r=eyJrIjoiNzE5YzczODItMDQzMS00M2EzLWFjNWYtMjg3OTY3NTNhZDM3IiwidCI6ImRjMWYwNGY1LWMxZTUtNDQyOS1hODEyLTU3OTNiZTQ1YmY5ZCIsImMiOjEwfQ%3D%3D&pageName=ReportSection32240d6b62ba73667e98 )
Read 9 tweets
Sep 22, 2024
Ceilings fans can reduce short-range viral concentrations close to the infected (54%-77%) while increasing long-range levels (5%-14%). Only recommended when # people in room is less than decision tool for various ventilation rates with not highly contagious pathogens (e.g. cold).

Decision tool for using or not using fans to mix the air in the room. Decision tool for using or not using fans under various ventilation rates (200, 400, and 800 m³/h) on reducing overall airborne transmission risk, considering occupants with and without the use of masks. The logarithmic scale on the left vertical axis shows the contagiousness of the pathogen, which indicates the quanta emission rate. The horizontal axis measures the number of people at long-range distances in relation to per person ventilation rates. The range of conditions that using fans is beneficial is filled in turqu...
The number concentration of lumped tracer particles between 0.3 and 5.0 μm for both short-range and long-range routes, respectively.
Link to full study here ( ).sciencedirect.com/science/articl…
There are some important caveats in this research. "Fans are beneficial in well-ventilated rooms with not highly contagious pathogens." 3/
Read 4 tweets

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