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Mike Hoerger, PhD MSCR MBA Profile picture
@michael_hoerger
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

Mike Hoerger, PhD MSCR MBA Profile picture
Jun 24
PMC COVlD Dashboard, Jun 23, 2025 (U.S.)

🔥Biggest uptick since Jan
🔥1 in 167 actively infectious
🔥>2 million weekly infections
🔥700-1,200 resulting excess deaths from weekly infections

Track transmission closer to home w/our new state & international resources 👇

🧵1/6
PMC COVlD Dashboard, Jun 23, 2025 (U.S.)

🔹With >90% probability, we have entered the 11th COVlD wave.
🔹In a room of 50 people, there is already a 1 in 4 chance of an exposure.
🔹We expect nearly 15 million infections in the next month, and rising.

🧵2/6Current Levels for Jun 23, 2025 % of the Population Infectious 0.6% (1 in 167) New Daily Infections 287000 New Weekly Infections 2009000 Resulting Weekly Long COVID Cases 100,000 to 402,000 Resulting Weekly Excess Deaths 700 to 1,200 Monthly Forecast Average % of the Population Infectious 1.0% (1 in 97) Average New Daily Infections 493300 New Infections During the Next Month 14799000 Resulting Monthly Long COVID Cases 740,000 to 2,960,000 Resulting Monthly Excess Deaths 5,300 to 8,800 Running Totals Infections Nationwide in 2025 74869000 Average Number of Infect...
PMC COVlD Dashboard, Jun 23, 2025 (U.S.)

We continue to expect transmission to break 500,000 daily infections in the U.S. around July 9th.

This is the same prediction as last week, as the forecast was dead on. Yet, there is considerably uncertainty around this timing.

🧵3/6Longitudinal transmission, past 12 months and 1-month forecast
Read 6 tweets
Mike Hoerger, PhD MSCR MBA Profile picture
Jun 17
1) PMC COVlD Dashboard, June 16, 2025 (U.S.)

Current transmission (red line) closely tracks that of summer 2023 (yellow line).

We expect to break 500k daily infections between July 9 and the end of July. Our current forecast...Year over year graph of tranmission
2) PMC COVlD Dashboard, June 16, 2025 (U.S.)

Our current forecast is a bit more aggressive, predicting breaking 500k daily infections by July 9. The 2023 trend suggests end of July.

The 95% confidence interval shows large variation. Note that...Past 12 months of transmission (U.S.) and forecast
3) PMC COVlD Dashboard, June 16, 2025 (U.S.)

Note that CDC and Biobot both had retroactive corrections to last week's data, meaning the relative "lull" will last a little longer than the uncorrected data suggested. No big news on NB.1.8.1.

All good news, but...10 pandemic waves. Soon 11
Read 7 tweets
Mike Hoerger, PhD MSCR MBA Profile picture
Jun 16
1) Here's a quick example of how the federal government is censoring the best scientific research. It's not just cuts to ongoing research.

It's new grant submissions too... "No forbidden words found"
2) In January, I re-submitted a promising Covid/cancer grant to a non-federal funder. Hundreds of pages. Hundreds of hours of work. The best proposal I've submitted as a scientist.

Out of curiosity, I used Sean Mullen's Scan Assist tool to see how many banned words it had...
3) The proposal had 1,750 banned words. No big deal -- they're non-federal.

BUT I had planned to submit a smaller version to NIH this month as a "back up." Impossible!

It's not a matter of using a thesaurus or the find/replace command. The grant is on *Covid*... 1,750 banned words found
Read 13 tweets
Mike Hoerger, PhD MSCR MBA Profile picture
Jun 9
1) PMC COVlD Dashboard, June 9, 2025

CDC wastewater surveillance data show transmission rising. This is our forecast if transmission growth follows typical patterns.

The high & low estimates could be thought of as optimistic & pessimistic scenarios for NB.1.8.1.Forecast graph: Rising transmission the next month
2) PMC COVlD Dashboard, June 9, 2025

Notice that current transmission (red line, lower left) tracks closely with two years ago (yellow), slightly below the median (gray), and not far below last year (orange).

Consider each of these trajectories realistic scenarios.Image
3) PMC COVlD Dashboard, June 9, 2025

All indications are that we are headed into the start of an 11th national wave in the U.S.

We could percolate near the lull point another couple weeks (fingers crossed), but that scenario is becoming less likely.Graph of 10 C19 waves
Read 7 tweets
Mike Hoerger, PhD MSCR MBA Profile picture
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
Mike Hoerger, PhD MSCR MBA Profile picture
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

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