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Jeff Gilchrist
@jeffgilchrist.bsky.social
6.9K followers 240 following 1.3K posts
PhD Biomedical researcher, data scientist, and finder of large prime numbers. Views are my own. Twitter: @jeffgilchrist Mastadon: @jeffgilchrist@mstdn.science

COVID-19 guides, stats, calculators & 600+ scientific articles: http://covid.gilchrist.ca
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Jeff Gilchrist @jeffgilchrist.bsky.social · Nov 10
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 )
Reposted by Jeff Gilchrist
jeffgilchrist.bsky.social
How does various mask fit compare to filter the air and protect you or others?

Most masks, even baggy blue procedure masks use filtering material that can filter 95%+ of particles that pass through it, but the key is "pass through it". Continue to learn more... 🧪🧵1/
Bar chart titled “Equivalent Exposure Time to Unmasked Person.” The chart compares how long different masks/respirators extend the equivalent exposure time relative to being unmasked. The x-axis shows unmasked infection times of 1, 5, and 10 minutes. The y-axis shows equivalent masked exposure time, ranging up to 5000 minutes. Seven mask types are represented by colored bars: - Procedure mask (loose fit, FF=2) - Ear loop mask (tight fit, FF=6) - Vertical bifold headband mask (FF=30) - N95 headband masks with fit factors of 100, 200, and 500 Key pattern: higher fit factor masks dramatically increase equivalent exposure time. For example, at 10 minutes unmasked, a procedure mask extends exposure to 20 minutes, while an N95 with FF=400 extends it to 5000 minutes.
October 25, 2025 at 11:09 AM
Reposted by Jeff Gilchrist
epiellie.bsky.social
What was life really like before vaccines? The story of what happened to 8-year old George Williams in August 1852 gives us a glimpse.

open.substack.com/pub/epiellie...
Here's what life before vaccines was really like
The morning of August 2nd 1852 promised a lovely summer’s day in London. But not for 8 year old George Williams.
open.substack.com
October 26, 2025 at 2:11 PM
jeffgilchrist.bsky.social
How does various mask fit compare to filter the air and protect you or others?

Most masks, even baggy blue procedure masks use filtering material that can filter 95%+ of particles that pass through it, but the key is "pass through it". Continue to learn more... 🧪🧵1/
Bar chart titled “Equivalent Exposure Time to Unmasked Person.” The chart compares how long different masks/respirators extend the equivalent exposure time relative to being unmasked. The x-axis shows unmasked infection times of 1, 5, and 10 minutes. The y-axis shows equivalent masked exposure time, ranging up to 5000 minutes. Seven mask types are represented by colored bars: - Procedure mask (loose fit, FF=2) - Ear loop mask (tight fit, FF=6) - Vertical bifold headband mask (FF=30) - N95 headband masks with fit factors of 100, 200, and 500 Key pattern: higher fit factor masks dramatically increase equivalent exposure time. For example, at 10 minutes unmasked, a procedure mask extends exposure to 20 minutes, while an N95 with FF=400 extends it to 5000 minutes.
October 25, 2025 at 11:09 AM
jeffgilchrist.bsky.social
** Ontario Variant Update (to Oct. 3, 2025) **

The XFG.* "Stratus" family is accounting for 83% while the next closest variant family NB.1.8.1.* "Nimbus" is 12.8% of sequenced genomes from COVID tests. 🧵1/
Line graph showing COVID-19 variant family frequencies in Ontario, Canada, from June to October 2025, based on 3,722 sequenced genomes.
October 19, 2025 at 12:18 PM
jeffgilchrist.bsky.social
Health Canada has published Guidance for Indoor Air Quality Professionals, a practical, science-based resource for Indoor Air Quality (IAQ) experts, building operators, and employers.

Article ( ospe.on.ca/advocacy/pol... )

Guidelines ( www.canada.ca/en/health-ca... )
Policy Win: Health Canada Releases New IAQ Guidance
Health Canada announces new IAQ guidance, providing essential insights for improving indoor air quality and safety in buildings.
ospe.on.ca
October 15, 2025 at 8:14 PM
Reposted by Jeff Gilchrist
jbloomlab.bsky.social
In new study led by @bdadonaite.bsky.social, we measure how spike mutations affect function & antigenicity of spike of KP.3.1.1 strain of SARS-CoV-2.

Sheds light on how key neutralizing epitopes are changing & importance of RBD up/down motion.

www.biorxiv.org/content/10.1...
Spike mutations that affect the function and antigenicity of recent KP.3.1.1-like SARS-CoV-2 variants
SARS-CoV-2 is under strong evolutionary selection to acquire mutations in its spike protein that reduce neutralization by human polyclonal antibodies. Here we use pseudovirus-based deep mutational sca...
www.biorxiv.org
August 20, 2025 at 5:22 AM
Reposted by Jeff Gilchrist
jbloomlab.bsky.social
The final published version of this study is now available in Journal of Virology at journals.asm.org/doi/10.1128/...
Spike mutations that affect the function and antigenicity of recent KP.3.1.1-like SARS-CoV-2 variants | Journal of Virology
This study measures how mutations to the spike of a SARS-CoV-2 variant that circulated in early 2025 affect its function and recognition by both the polyclonal antibodies produced by the human immune ...
journals.asm.org
October 14, 2025 at 4:22 PM
Reposted by Jeff Gilchrist
jbloomlab.bsky.social
In new study led by @ckikawa.bsky.social, we provide near real-time data on human neutralizing antibody landscape to influenza by measuring ~26,000 titers to >100 recent viral strains

Data can inform vaccine selection & evolutionary/epidemiological modeling
www.biorxiv.org/content/10.1...
Near real-time data on the human neutralizing antibody landscape to influenza virus to inform vaccine-strain selection in September 2025
The hemagglutinin of human influenza virus evolves rapidly to erode neutralizing antibody immunity. Twice per year, new vaccine strains are selected with the goal of providing maximum protection again...
www.biorxiv.org
September 8, 2025 at 9:48 PM
Reposted by Jeff Gilchrist
brendancrabb.bsky.social
Such an important piece. The positive momentum behind clean indoor air is palpable. But we’re not there yet as my last post demonstrates. Please read and share and get behind this cause.

theconversation.com/why-investme...
Why investment in clean indoor air is vital preparation for the pandemics and climate emergencies to come
Unchecked airborne infections cost billions in lost health and productivity each year – likely more than the cost of better ventilation to clean up indoor air.
theconversation.com
October 1, 2025 at 11:12 PM
jeffgilchrist.bsky.social
I found out for Ontario that "the Ministry of Health updated the age groups on the I9 bed census data collection forms" so some data in the Ontario Respiratory Virus Tool ( www.publichealthontario.ca/en/Data-and-... ) will be grouped differently starting in September. 🧵1/
Table of age groups before September 2025 Table of age groups starting September 2025
September 29, 2025 at 12:22 PM
Reposted by Jeff Gilchrist
smcgrath.phd
🧪 Can researchers stop AI from fabricating citations? Probably not entirely.

While models like GPT-5 are improving, hallucination is fundamental to their statistical design, shifting the burden onto users to build new intuitions for an AI age.
#MLSky #AcademicSky
Can researchers stop AI making up citations?
OpenAI’s GPT-5 hallucinates less than previous models do, but cutting hallucination completely might prove impossible.
www.nature.com
September 9, 2025 at 3:27 PM
jeffgilchrist.bsky.social
*** Ontario Variant Update (to: Aug. 16, 2025) ***

Ontario COVID sequence updates have been more frequent over the past month with the XFG.* "Stratus" family of variants now at 74% of sequences, NB.1.8.1.* "Nimbus" at 22% and LP.8.1.* down to 3%. #Variants #COVID #XFG #Stratus 🧪🧵1/
Line graph showing COVID-19 variant frequencies in Ontario, Canada, from May to mid August 2025, based on 1,772 sequenced genomes. The XFG.* Stratus variant rises sharply to dominate over 70% by August. Other variants, including FLiRT and LP.8.1.*, decline over the same period, while NB.1.8.1.* Nimbus remains steady around 20% and several minor variants remain at low levels.
September 9, 2025 at 12:08 PM
Reposted by Jeff Gilchrist
ryanhisner.bsky.social
A fascinating new preprint w/one very unexpected finding suggests, I believe, that a large proportion of Long Covid may be due to chronic infection in a particular bodily niche, which could be crucial for finding effective LC treatments. It requires some explaining. 🧵 1/33
September 2, 2025 at 3:16 AM
Reposted by Jeff Gilchrist
donatemask.bsky.social
For the next little while, all donations will be matched by a generous corporate sponsor.

That means your donation will go twice as far–so donate today!

#DoubleYourImpact #YallMasking
August 27, 2025 at 5:01 PM
Reposted by Jeff Gilchrist
nbcovidinfo.bsky.social
This links to a press release - we need some media coverage, yo! Please send the press release out to Canadian journos. 💕 thank you! #cdnpoli #nbpoli #ableg #nspoli #peipoli
nbcovidinfo.bsky.social NB COVID info @nbcovidinfo.bsky.social · Aug 27
#Z94.4
The Canadian Aerosol Transmission Coalition put out a statement supporting CSA’s revisions to Z94.4. Over 1,700 individuals and organizations signed on to the statement - including unions representing over 3 million workers in 🇨🇦. www.globenewswire.com/news-release...
Protecting healthcare workers protects us all:
Canadian coalition gets overwhelming support backing stronger protections for healthcare workers in updated CSA respirator standard...
www.globenewswire.com
August 27, 2025 at 11:45 AM
Reposted by Jeff Gilchrist
donatemask.bsky.social
Thank-yous from our donors mean the world to us! 💙

Donate A Mask is 100% powered by volunteers, and knowing our work is helping others stay safe and healthy is what keeps us going! 😷

Consider donating to support our work.

donatemask.ca/fundraiser

#StillMasking and #StillSaltingTheVibes
"Thank you for keeping Canadians safe and healthy! - A donor from Vancouver, BC" Donate A Mask Canada / donatemask.ca Photo of a young Black man on a bus looking out a window. He is wearing a suit and a white N95 respirator mask.
August 24, 2025 at 10:09 PM
Reposted by Jeff Gilchrist
donatemask.bsky.social
DYK our Free Request Program offers respirator #masks in 5 different styles & multiple sizes, including small masks for kids? 😷

Consider donating to support our Free Request Program. Right now, every dollar will be matched by our corporate sponsor!

donatemask.ca/fundraiser

#MaskUp #StillMasking
"DYK: Our Free Request Program offers respirator masks in 5 different styles and multiple sizes, including small masks for kids?" Donate A Mask Canada / donatemask.ca Photo of two white respirator masks on a light blue table. One is a flat fold earloop KN95 and the other is a cup-style N95.
August 23, 2025 at 11:13 PM
Reposted by Jeff Gilchrist
donatemask.bsky.social
If #masks and clean air tools are on your back-to-school shopping list, consider stocking up at our charity fundraising store. 🛍️

🛒 donatemask.ca/shop

Our kid-sized masks are on sale at super low prices! 😷

#CleanAirForAll #MaskUp
"Back to School Sale - buymask.ca / Vitacore Children's CAN99e Earloop Respirators" on a white ripped piece of paper. The background is of illustrations of school supplies and items. Donate A Mask’s logo is in the top right corner.
August 18, 2025 at 1:56 AM
Reposted by Jeff Gilchrist
donatemask.bsky.social
New fundraiser alert! 📢 Woot woot!

A very generous corporate sponsor has agreed to match all donations we receive up to $2,000! 🎉

So donate today to amplify your impact—every $1 we receive will turn into $2! 😷

donatemask.ca/fundraiser

#YallMasking #WearAMask
"Donate Today! A generous corporate sponsor will match all donations up to $2,000. Donate A Mask Canada Matching Fundraiser. donatemask.ca/fundraiser" Photo of a young girl with long blond hair in two pigtails wearing a white N95 respirator. She is looking at the camera and giving a thumbs up.
August 15, 2025 at 6:17 PM
Reposted by Jeff Gilchrist
jeffgilchrist.bsky.social
Understanding Canadian Air Quality Health Index (AQHI) & Wildfire Smoke

Wildfire smoke consists of toxic gases and particulate matter (PM) when breathed in gets into our lungs, bloodstream, and even our brain. 🧪🧵1/
#IAQ #IndoorAirQuality #wildfire #smoke #AQI #AQHI #Canada
Bar chart of Canadian Air Quality Health Index (AQHI) - Equivalent # Cigarettes after Exposure ranging from 0.5 cigarettes after 8 hours exposure at AQHI level 3 to 0.9 cigarettes at level 6 and 1.5 at level 10. Bar chart of Canadian Air Quality Health Index (AQHI) - Equivalent # Cigarettes after Exposure ranging from 0.5 cigarettes after 8 hours exposure at AQHI level 3 to 0.9 cigarettes at level 6 and 1.5 at level 10.
June 9, 2025 at 2:23 PM
jeffgilchrist.bsky.social
Here is your chance to provide constructive feedback on the proposed updated Canadian Standards Association (CSA) respirator standard which calls for universal respirator use in healthcare settings & when performing patient care outside of healthcare settings (eg – in the home).
barryhunt008.bsky.social Barry Hunt @barryhunt008.bsky.social · Jul 25
How you can help:

The draft CSA Z94.4 Standard is now out for Public Review until August 19, 2025.

Please weigh in with your positive, constructive comments at publicreview.csa.ca/Home/View/22... .

Public Review comments are open to everyone who registers.
Log in | CSA Public Review System
publicreview.csa.ca
July 26, 2025 at 1:25 PM
Reposted by Jeff Gilchrist
barryhunt008.bsky.social
How you can help:

The draft CSA Z94.4 Standard is now out for Public Review until August 19, 2025.

Please weigh in with your positive, constructive comments at publicreview.csa.ca/Home/View/22... .

Public Review comments are open to everyone who registers.
Log in | CSA Public Review System
publicreview.csa.ca
July 25, 2025 at 4:21 PM
Reposted by Jeff Gilchrist
barryhunt008.bsky.social
Good News!

Canadian Standards Association (CSA) has called for universal respirator use in healthcare settings & when performing patient care outside of healthcare settings (eg – in the home) in the latest edition of CSA Z94.4, Selection, use and care of filtering respirators.
July 25, 2025 at 4:21 PM
jeffgilchrist.bsky.social
Interesting comparison of different PM sensors outside the lab. Great customer service to replace with a better functioning model.
visiblair.bsky.social VisiblAir @visiblair.bsky.social · Jul 16
🚨 Model X2 Update! 🚨
The SEN66 sensor was a bit too chill about wildfire smoke. 😬
We ran tests. We saw the issue.
The new Model X2 will use SEN55 + SCD30 for better outdoor PM.
🎁 Free replacement for all X2 owners!
📖 visiblair.com/products/rea...
#AirQuality #WildfireSmoke
Real-World PM Sensor Testing - Summer 2025
🎯 Goal of the Testing We conducted these real-world tests following field reports that the Model X2, which uses the Sensirion SEN66 sensor, may be under-reporting particulate matter (PM) levels—especi...
visiblair.com
July 16, 2025 at 3:02 PM
Reposted by Jeff Gilchrist
visiblair.bsky.social
🚨 Mise à jour Model X2 ! 🚨
Le capteur SEN66 aime la poussière, mais la fumée dehors ? Il fait semblant de rien.😅
On a testé, confirmé, et réglé.
Le nouveau X2 aura SEN55 + SCD30.
🎁 Échange gratuit pour tous les proprios !
📖 visiblair.com/fr/products/...
#AirQuality #WildfireSmoke
Real-World PM Sensor Testing - Summer 2025
🎯 Goal of the Testing We conducted these real-world tests following field reports that the Model X2, which uses the Sensirion SEN66 sensor, may be under-reporting particulate matter (PM) levels—especi...
visiblair.com
July 16, 2025 at 2:06 AM