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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
Aug 21
During times like these when COVlD transmission heats up in the U.S., expect to see a lot more angry outbursts for three central reasons.

First, "displacement," or people trying to deny the reality of their anxiety by taking it out on other people....
Second, a lot of people can sustain a strong denial of reality about the ongoing pandemic during lulls. They suppress the existence of COVlD waves and excess deaths, disability, and retirements.

During waves, those defenses burst. Loss of control = anger...
Third, a lot of people (many reading this) understand COVlD correctly & experience righteous indignation during COVlD waves. We quite reasonably do not like all of the unjust and gratuitous suffering.

I find it helpful to channel that intensity into helping other people....
Read 6 tweets
Mike Hoerger, PhD MSCR MBA Profile picture
Aug 19
I submitted my comment to endorse universal high-quality masks (respirators) in healthcare. Today is the final day.

Alt text continues in the following posts. RE: Z94.4, Selection, use, and care of respirators (New Edition) Dear Colleagues, As the director of a population science program at a major U.S. cancer center, I strongly endorse this draft proposal to increase the use of high-quality well-fitting masks (respirators) in medical settings. I will comment on the relevance of this proposal mainly for cancer care. In the U.S., cancer care is commonly more organized than other specialty care and, thus, often leads the way on policy initiatives, which then translate to other elements of care over time. 1. COVID-19 continues to cause excess dea...
They put forth projections, with the most granular detail for the U.S. and U.K., suggesting excess deaths will persist through at least 2033. Their projections do not show excess deaths stopping in 2033; that is simply the final year of their current analysis. Moreover, while they provide the most data for the U.S. and U.K., their analysis suggests a more general trend throughout the globe. The COVID-19-associated excess deaths are commonly identified as cardiovascular and cancer causes of death. Swiss Re Institute. (2024). The future of excess mortality after COVID-19. https://www.swissr...
Alt text continued 2. The SARS-CoV-2 virus that causes COVID-19 continues to transmit at high rates worldwide. Overall, 28 nations continue to use wastewater surveillance to monitor SARS-CoV-2 levels. A directory is available at the dashboard that I oversee (pmc19.com/data). In the U.S., we are currently experiencing our 11th wave of transmission. Many nations are experiencing annual or twice annual waves of transmission.
Alt text continued 3. International consensus standards identify a broad range of patients at known high-risk of severe outcomes of COVID-19. The largest group at known high risk of severe outcomes is patients with cancer. Other diagnoses associated with above average risk include people undergoing transplants or receiving dialysis, and patients with any of these diagnoses: immunodeficiencies, renal disease, systemic-immune mediated or single-site immune-mediated inflammatory conditions, asplenia, anatomical barrier defects, pregnancy, and diabetes. These findings underscore the importance of standards in hea...
Read 7 tweets
Mike Hoerger, PhD MSCR MBA Profile picture
Aug 16
🚩🚩🚩
As a vigorous defender of #CDC data, their switch from using normalized to non-normalized COVlD wastewater surveillance data today harms data quality.

"Normalizing" means accounting for basic confounders like rain levels. It is a choice to use worse data.
1/5🧵 Image
Historically, the CDC data have correlated near-perfectly with similar metrics, such as Biobot's wastewater estimates (still active) or the IHME true case estimates (through mid-2023).

The changes reduce those correlations. It's like going from an A+ to a B.

2/5🧵
You can readily see the loss of data quality in the PMC "whole pandemic" graph (preview shown, subject to change) with choppier waves, caused by the CDC adding extra noise to the data and applying retroactively from BA.1 Omicron to present.

3/5🧵 Longitudinal graph of the pandemic waves. Notice how they start becoming choppier in 2022, as a result of today's changes at the CDC
Read 5 tweets
Mike Hoerger, PhD MSCR MBA Profile picture
Aug 12
PMC COVID Dashboard, August 11, 2025 (U.S.)

The CDC says transmission is heating up.

"Very High" (3)
🔺Guam
🔺Hawai'i
🔺Louisiana

"High" (12)
🔺Alabama
🔺Alaska
🔺California
🔺Colorado
🔺Delaware
🔺Florida
🔺Indiana
🔺Mississippi
🔺Nevada
🔺S. Carolina
🔺Texas
🔺Utah

🧵1/12Heat map from CDC data. High/Very high states noted in post
Transmission is highest in these regions. Graphics note the CDC levels and PMC prevalence estimates.

🔥Louisiana (Very High): 1 in 19 actively infectious
🔥Guam (Very High): 1 in 26
🔥Hawai'i (Very High): 1 in 28
🔥Texas (High): 1 in 45

🧵2/12 Graphics show heat maps and prevalence estimates, noted in the post
Statewide transmission remains "High" in Florida, according to the CDC. PMC estimates 1 in 50 actively infectious.

Several cities report "Very High" transmission. Several sites are offline.

🧵3/12 Heat map and prevalence estimate noted in the post
Read 12 tweets
Mike Hoerger, PhD MSCR MBA Profile picture
Jul 29
PMC COVID Dashboard, July 28, 2025 (U.S.)
🧵1/12

PMC estimates 400,000 new daily infections. 1 in 118 people actively infectious.

Weekly stats:
🔹2.8 million infections (>40x reported cases)
🔹>140,000 resulting #LongCOVID cases
🔹>1,000 resulting excess deaths Heat map Very High: Louisiana, Guam High: Hawai'i, Florida
PMC COVID Dashboard, July 28, 2025 (U.S.)
🧵2/12

Please excuse any typos and delays. Any time Mimal's boot turns deep red, we're doing local outreach in addition to dashboard work, etc.

If you don't know Mimal yet, you won't be able to unsee them.
es.wikipedia.org/wiki/MIMALDeep red boot = Louisiana
Minnesota (M), Iowa (I), Missouri (M), Arkansas (A), Louisiana (L) = Mimal Louisiana is the boot. Sometimes depicted with Kentucky fried chicken on a Tennessee pan.
PMC COVID Dashboard, July 28, 2025 (U.S.)
🧵3/12

It's HOT COVID SUMMER in the Deep South. No geographic/political prejudices, see next.

Covid is burning through Guam, Louisiana, Florida, and Texas (underestimate due to sites down). Louisiana: 1 in 32, Very High (CDC)
Texas: 1 in 98, Moderate (underestimate, CDC)
Guam: 1 in 25, Very High (CDC)
Florida: 1 in 59, High (CDC)
Read 12 tweets
Mike Hoerger, PhD MSCR MBA Profile picture
Jul 25
U.S. CDC numbers just released. Good news (for those not in Louisiana). "Only" a 5% national increase.

2025 has closely tracked with summer 2023 transmission. A 12-13% increase would have been expected based on those numbers. That said... Up: Midwest, Northeast Down: West, South
real-time data have been prone to retroactive corrections. This is frustrating, of course, because it leaves people making decisions based on data that are only of good quality when 2 weeks old.

If we saw a 12% increase this week, I'd say look at 2023 for a glimpse...
at the future. Instead, I would consider these plausible scenarios:
🔹Wave still similar to 2023
🔹Later wave with schools more implicated
🔹Something temporarily much better

Of course, temporarily better often means...
Read 6 tweets

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