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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
Jul 15
1) PMC COVlD Dashboard, July 14, 2025 (U.S.) 🧵

We estimate 1 in 148 Americans are actively infectious. This equates to 2.3 million infections/week, expected to result in >100,000 new #LongCOVID conditions & >800 deaths.

A room of 100 people is a coin toss of an exposure. Figure shows each wave of the pandemic. Tables: Current Levels for Jul 14, 2025 % of the Population Infectious 0.7% (1 in 148) New Daily Infections 324000 New Weekly Infections 2268000 Resulting Weekly Long COVID Cases 113,000 to 454,000 Resulting Weekly Excess Deaths 800 to 1,300 Monthly Forecast Average % of the Population Infectious 1.3% (1 in 80) Average New Daily Infections 598766.6667 New Infections During the Next Month 17963000 Resulting Monthly Long COVID Cases 898,000 to 3,593,000 Resulting Monthly Excess Deaths 6,400 to 10,700 Running Totals Infection...
2) PMC COVlD Dashboard, July 14, 2025 (U.S.) 🧵

Transmission (red) is closely tracking the path of 2 years ago (yellow). However, the incoming data are spotty. >20% of CDC states have limited/no data, & Biobot hasn't reported in weeks.

Could be MUCH worse or slightly better. Graph of year over year transmission. The current year (red) is tracking the path of two years ago (yellow) extremely closely. Two years ago, the peak was around September 1, at about 1 million daily estimated infections, and significantly higher than the Delta wave (blue).
3) PMC COVlD Dashboard, July 14, 2025 (U.S.) 🧵

Our model formalizes the mathematical assumptions in those predictions. If transmission follows what we know in terms of how waves grow or slow generally and historical patterns, this is what we'd expect.

The spottiness of the current real-time data reduce precision substantially. Retroactive corrections can make the forecast jump around from better to worse from one week to the next. Expect the worst. Hope for the best.Graph shows national transmission expected to increase the next several weeks.
Read 11 tweets
Mike Hoerger, PhD MSCR MBA Profile picture
Jul 2
🌍Want to track COVID transmission accurately worldwide?

This PMC thread walks you through leading dashboards with information more up to date than WHO & EU directories.

🧵 1/ World map, countries with high-quality up-to-date surveillance systems shown in blue.
The Pandemic Mitigation Collaborative (PMC) Dashboard provides weekly COVID updates for the U.S., using wastewater surveillance derived case estimation models and analytic forecasting.

We have added a list of international dashboards:
🧵 2/
pmc19.com/data/index.php…Australia: NSW Health Australia Department of Health, Western Australia Austria: Federal Government of Austria City of Vienna - Regional Coron-A Consortium Austria Czech Republic: State Health Institute Czech Republic Belgium: Belgian Institute for Health Canada: Government of Canada Andrew Young's Canada Visualization C19 Resources Canada * World Health Network (WHN) Canada **
Denmark: Statens Serum Institut Denmark Europe (multi-national): EU Wastewater Observatory Finland: National Institute for Health and Welfare Finland WHN Finland ** France: French Republic Data Airborne Risk Reduction Association (ARRA) France Zan Armstrong's France Visualization COVID Weather App France (Android, IOS, or Web) Thomas Delattre's France Visualization Germany: Infection Radar Germany Bay-VOC Bavaria Region Berlin Waterworks WHN Germany **
Hong Kong: Centre for Health Protection, Hong Kong Hungary: National Center for Public Health and Pharmacy of Hungary India: Pune Knowledge Cluster of India Gujarat Biotechnology Research Centre of India Ireland: Health Protection Surveillance Centre Ireland Japan: Japan Institute for Health Security Latvia: Institute of Food Safety, Animal Health and Environment Latvia Lithuania: National Public Health Centre of Luthuania Luxembourg: Microbs Luxembourg Netherlands: National Institute for Public Health and the Environment Netherlands WHN Netherlands ** New Zealand: New Zealand Institute for...
Slovenia: National Institute of Public Health Slovenia Spain: Government of Catalonia - Regional South Africa: National Institute for Communicable Diseases of South Africa South Korea: Korea Disease Control and Prevention Agency Sweden: Pathogens Sweden Switzerland: Swiss Confederation Federal Office of Public Health ETH Zurich Switzerland WISE Dashboard U.K.: Public Health Scotland Buckinghamshire Disability Service (BuDS) U.K. *See the numbers 1-21 along the lower left. Click on 3-6 for national and regional data. ** Click on the dropdown menu. May need to try a different web browser.
Our international directory includes official government dashboards & those developed by citizen scientists.

We exclude countries that have stopped reporting in the past 2-12 months even if on EU or WHO lists. We also exclude low-quality data from opt-in testing programs.
🧵 3/
Read 43 tweets
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

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