Mike Hoerger, PhD MSCR MBA Profile picture
Jul 14, 2022 10 tweets 10 min read Read on X
Kids <2 yrs old can’t mask.
Kids <6 months can’t vax.

Many parents are using strollers w/rain covers to try to get some protection during essential activities.

Does adding a #PAPR or #HEPA device help?

I tried 6 models: engrxiv.org/preprint/view/…

#PAPRbuggy #HEPAbuggy
1/10 Image
First off, thanks @RealSexyCyborg for the original design. Thanks to @ccwake1, @gjmf, @drgregkelly for ideas too. Happy to acknowledge!

My goal was to test 6 models & help relate them to non-engineers.

2/10

The PAPR & HEPA buggies I tested had an estimated 57-951 air changes per hour (ACH) in these TINY spaces. The worst design had about 3x the air cleaning of an OR.

You can make a #PAPRbuggy that’s super discrete for about $110 more than an existing stroller & rain cover.

3/10 Image
With even a cheapo ($55) HEPA, you can make a relatively discrete #HEPAbuggy w/good air cleaning (see Figure A1.5 in preprint).

BUT, I also tested some power models. This one runs at an estimated 900+ ACH, or about 60x the minimum rate of an OR. 😎 Vroom vroom.

4/10
Want to learn more about a #PAPRbuggy or #HEPAbuggy?

See the preprint:
🔸 Figure A1: Design ideas
🔸 Tables 1 & A4: Estimated specs
🔸 Table A3: Parts & supplies w/links
🔸 Tables A1-A2: Help w/any calculations

engrxiv.org/preprint/view/…

5/10 Image
If you are a COVID-cautious parent, be forearmed that trolls will troll.

Sticks & stones. I knight you a #PublicHealth ambassador. Stand tall. Your work is needed.

Check out Table A5 for what to expect (final page).
engrxiv.org/preprint/view/…

6/10
If you’re a #COVID-cautious #parent, I also hope you’ll read the 1st paragraph of this paper (pg. 3).

✅ You’re doing the right thing
✅ You’re smart
✅ Feel validated
✅ Reference #7 is absolutely damning
✅ Kids deserve a better world

engrxiv.org/preprint/view/…

7/10
H/t 🎩to @sri_srikrishna for the #CorsiRosenthalBox article that inspired my write up.
sciencedirect.com/science/articl…

Thanks also to @JimRosenthal4, @CorsIAQ, @joeyfox85, and others for teaching about air cleaning

8/10
I posted Naomi’s original design, but also check out Greg’s "Pram-PAPR." He’s got a different air filter & older child.

Mine are baby twins, so I’ve got some different models in the paper & will test out more double strollers down the line too.

9/10
Thank you for your advocacy - @MamaWeasleyy, @PTF_org, @Annalisa840917, @mir_ocall, @maskupmama, #ImmunizeUnder5s #covidkids

Please share the #PAPRbuggy & #HEPAbuggy with families of young children!

If I have to 🔒 my account, send the link:
engrxiv.org/preprint/view/…

10/10

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More from @michael_hoerger

Jun 3
1/ PMC COVlD Dashboard, June 2, 2025 (U.S.)

National COVlD transmission recently fell to its lowest levels since the pre-Delta era.

It's go-time for many who have delayed medical appointments. The situation will likely get much worse in Jul/Aug.
2/ PMC COVlD Dashboard, June 2, 2025 (U.S.)

An estimated 1 in 211 are actively infectious. Most states are "low" or "very low" per CDC.

The situation remains serious even in a relative "lull." >1.5 million weekly estimated infections to result in 600-900 excess deaths.C19 heat map
year over year graph, tracking closely with the median and past 2 years
Current Levels for Jun 2, 2025	 % of the Population Infectious	 0.5% (1 in 211)	 New Daily Infections	 227000	 New Weekly Infections	 1589000	 Resulting Weekly Long COVID Cases	 79,000 to 318,000	 Resulting Weekly Excess Deaths	 600 to 900	 	 Monthly Forecast	 Average % of the Population Infectious	 0.7% (1 in 139)	 Average New Daily Infections	 344566.6667	 New Infections During the Next Month	 10337000	 Resulting Monthly Long COVID Cases	 517,000 to 2,067,000	 Resulting Monthly Excess Deaths	 3,700 to 6,200	 	 Running Totals	 Infections Nationwide in 2025	 70132000	 Average Number of Infe...
Graph of the whole pandemic, 11th wave forthcoming
3/ PMC COVlD Dashboard, June 2, 2025 (U.S.)

By the end of the month, we forecast an increase to 450k daily infections. If NB.1.8.1 takes off, closer to 600k. If overhyped, percolating only slightly higher.Past 12 months and forecast
Read 5 tweets
May 26
1) PMC Dashboard, May 26, 2025 (U.S.)

The lull exit is coming. Despite being in a lull:

🔥1 in 180 actively infectious
🔥1.9 million weekly infections
🔥>93,000 new #LongCOVID cases from the week's infections
🔥1,100 excess deaths from the week's infections

This is a "lull."
2) PMC Dashboard, May 26, 2025 (U.S.)

The forecast calls for a near-doubling in transmission the next month to 450k daily infections.

The 95% confidence interval includes flat transmission (percolating), or escalating to 650k (if NB.1.8.1 takes off). Forecasting graph, summarized in post
3) PMC Dashboard, May 26, 2025 (U.S.)

Looking at year-over-year transmission, 2025 (red) is closely tracking the median (gray).

It transmission accelerates, it could look more like last year (orange). If it slows, more like two years ago (yellow). Year-over-year graph summarized in post
Read 7 tweets
May 25
1) CDC & Biobot wastewater surveillance both show the West region in an apparent uptick in C19 transmission.

Here's the graph of regional transmission from CDC data with the West in green: Estimated Percentage Actively Infectious*						 		PMC Model		Raw CDC Data		 	National	0.6% (1 in 180)		0.5% (1 in 196)		 	Northeast	0.4% (1 in 236)		0.4% (1 in 257)		 	Midwest	0.5% (1 in 209)		0.4% (1 in 227)		 	South	0.6% (1 in 160)		0.6% (1 in 175)		 	West	0.8% (1 in 129)		0.7% (1 in 140)
2) This image zooms in on the West (green line) so you can see the apparent departure from the C19 lull more easily. Zoomed in graph from prior post. More stats in the ALT text there.
3) Biobot still provides national & regional C19 updates. They usually post sometime between Thursday morning & Saturday evening. IMO, their most recent data point can be viewed as the Wednesday of the prior week.

Like the CDC, they have an apparent uptick in the West (green). Biobot graph. What's striking is that the peak (for any region) is almost identical the past 3 waves, though the West apparently runs cooler on average. The West is presently highest and increasing, whereas the other regions are lower and still trending down at the time of these data.
Read 6 tweets
May 20
PMC COVlD Report, May 19, 2025 (U.S.)

In this national "lull" in transmission, we are seeing...
🔥A quarter-million daily infections
🔥90-360k Long COVlD cases from the week's infections
🔥600-1,100 deaths from the week's infections
🔥LA, SD, NE, & GU in high transmission10 waves of C19
Heat map, summarized in post
Current Levels for May 19, 2025	 % of the Population Infectious	 0.5% (1 in 185)	 New Daily Infections	 259000	 New Weekly Infections	 1813000	 Resulting Weekly Long COVID Cases	 91,000 to 363,000	 Resulting Weekly Excess Deaths	 600 to 1,100	 	 Monthly Forecast	 Average % of the Population Infectious	 0.8% (1 in 129)	 Average New Daily Infections	 371566.6667	 New Infections During the Next Month	 11147000	 Resulting Monthly Long COVID Cases	 557,000 to 2,229,000	 Resulting Monthly Excess Deaths	 4,000 to 6,600	 	 Running Totals	 Infections Nationwide in 2025	 66986000	 Average Number of I...
Year-over-year graph, currently closely tracking the median, Y4, and Y5
Full report: pmc19.com/data
PMC COVlD updates are also posted periodically on Plip Plop:

tiktok.com/@michael_hoerg…
Read 6 tweets
May 15
1) Good luck getting any new federal research to support #LongCOVID until "covid" is dropped from the dirty words that get grant applications triaged to the trash bin.

You know which senator to call.

I just did, and got a staffer instead of voicemail.Lengthy list of words that get federal grants triaged to the trash bin, unfunded after favorable review, or defunded if already in progress.   Includes "Covid-19," and no, it's not a matter of simply restating as "SARS2" or "The Rona." It might make it one step further in the review process, but this gets checked closed, and it will get canned. Hundreds of hours of work, flushed down the toilet.   And that's the point.
2) I told the staffer that #LongCOVID is affecting millions and that no research will be funded to address this while "covid" remains on the banned word list.

I asked if they wanted to hear more. He did...

Here's the word list, btw
pen.org/banned-words-l…
3) I told them about my family member who was a strong Special Forces veteran, got covid once, & according to their neurologist, it triggered #LongCOVID in the form of Dementia w/Lewy Bodies.

DLB is one of the worst conditions imaginable. After a 2yr battle, they died in 2024.
Read 5 tweets
May 3
30 million excess deaths attributable to COVID is a tremendous underestimate because most analyses insufficiently account for mortality displacement.

In the U.S., it's about 50% worse than people realize.
Mortality displacement or "harvesting" is the idea that so many people died of COVID in the early pandemic that we should actually expect to see *fewer* deaths today if COVID were "over."
In fact, we see similar or slightly higher mortality relative to pre-pandemic levels. Despite the millions of people that have died, the mortality faucet keeps running strong. It should have slowed.
Read 9 tweets

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