Mike Hoerger, PhD MSCR MBA Profile picture
Sep 23, 2024 8 tweets 5 min read Read on X
PMC COVID-19 Forecasting Model, Sep 23, 2024
🧵 1/8

The U.S. continues to see an estimated 1.1 million daily COVID infections with 2.2% of the population actively infectious as we descend from the peak of a 9th Covid wave.

Transmission will remain very high the rest of 2024.Main PMC figure showing Covid transmission over time. It shows 9 waves. The current wave peaked in August, and we're still seeing >1 million infections/day in the U.S.
PMC COVID-19 Forecasting Model, Sep 23, 2024
🧵 2/8

Looking at the year-over-year graph, note that we're in uncharted territory for this point in the fall. Expect a very high "lull" in early November before the winter surge sets in.

As we have noted previously, our current estimates are likely slight underestimates given elevated school-based transmission and the CDC data standardization process.

Kids: They are smaller, and make smaller "contributions" to wastewater. Basically, it takes more sick kids to produce the average amount of wastewater virus to equate to an average infection (mostly in adults). This issue evens out over time, but it means the model may underestimate during back-to-school periods.

CDC: They describe the details of their process for standardizing data over time. It's very strong, much better than what most localized wastewater orgs or WWS do. It's a bit Dunning-Kruger to question basic wastewater scientists in doing the most fundamental components of their jobs, and the data continue to correlate >.90 with other metrics like Biobot. In comparing with other data, I take their estimates as spot on, but could also see arguments that they may underestimate transmission by 0-5%. It's something we always keep an eye on. Trust, but verify.

Transmission is magnitudes higher than much of the public realizes, so we focus on the big-picture view rather than quibbling over such issues that tend to balance out over time.

I hear @jlerollblues is considering weighting a model based on estimates of the proportion of infections in children. That's actually tougher to estimate than it sounds at first glance. You should key an eye on his models too and the work he and others are doing with the WHN.Estimating a "lull" the 1st week of November, but at an alarming 850k daily infections in the U.S.
PMC COVID-19 Forecasting Model, Sep 23, 2024
🧵 3/8

Zooming in from the big picture, here's the past year of the pandemic.

🔹1.1 million daily infections
🔹Bimodal peak (Aug 10 & 24) of 1.3 million daily infections
🔹50-60% of transmission happens on the back end of waves

Continue to educate family, friends, and co-workers. Look at how the wave descends much more gradually than is arose. Many infections to come, and to try to prevent! Also, most people are not monitoring wastewater. They keep track of the cumulative "anecdata" of people they know sick or diagnosed with Covid recently. In their mind, the peak will feel like late October, when the cumulative count has really built up. You may find people more open to listening during the next month.Annual graph. Shows transmission much higher than a year ago at 1.1 million daily infections today, but nowhere near the 1.9 million daily infections of last winter's peak.   The wave is descending slower than it rose, which is a reminder than much transmission happens on the back end of waves.
PMC COVID-19 Forecasting Model, Sep 23, 2024
🧵 4/8

These statistics document the ongoing toll of the pandemic.

🔥Expect about 29 million infections in the U.S. over the next month if the model holds.

🔥In a classroom of 30-35 people, there's about a 50% chance at least one person is infectious if weak/no isolation policies.

🔥Transmission is higher than during 80% of the pandemic.Current Levels for Sep 23, 2024 % of the Population Infectious 2.2% (1 in 45) New Daily Infections 1,059,000  New Weekly Infections 7,413,000  Resulting Weekly Long COVID Cases 371,000 to 1,483,000  Monthly Forecast Average % of the Population Infectious 2.0% (1 in 49) Average New Daily Infections 969,467 New Infections During the Next Month 29,084,000 Resulting Monthly Long COVID Cases 1,454,000 to 5,817,000  Running Totals Infections Nationwide in 2024 214,525,000 Average Number of Infections Per Person All-Time, U.S. 3.42  How Does Risk Increase with More Social Contacts? Number of peopl...
PMC COVID-19 Forecasting Model, Sep 23, 2024
🧵 5/8

Three states stand out.

Estimated percentage of populations actively infectious:

Oklahoma: 8.9%
Oregon: 5.3%
New Hampshire: 5.3%

Note, estimates get less precise when focusing on smaller geographic units, and sometimes high estimates are revised in hindsight.

Also, while these figures may seem high, keep in mind that as one focuses on narrower units, the peak is more targeted, so local peaks see higher percentages than state peaks, which are higher than regional peaks, which are higher than national peaks. Smaller units have more leptokurtic transmission.CDC heat map. Very high transmission across most of the U.S.
PMC COVID-19 Forecasting Model, Sep 23, 2024
🧵 6/8

These are the present regional estimates in the U.S.

The West is coming down from a second peak this wave but still with approximately 2.8% of the region actively infectious.

The Northeast region saw atypically low transmission this wave, relative to other regions. That area may see a different pattern of transmission than the rest of the U.S. the next several months. For example, within the northeast region, the winter peak could be larger than other areas. However, expect to also see more localized units where instead of 2 big waves (late summer and winter), there is 1 big wave in late Nov / early December, or a bumpy wave in the months ahead, like the west just saw. Last winter, we often posted examples of the "weird" transmission patterns in some areas.

I'd keep a closer eye on local data if in the Northeast region.Regional graph of transmission from the CDC.  Table from PMC  Estimated Percentage Actively Infectious National	2.2% (1 in 45) Northeast	1.2% (1 in 85) Midwest	2.4% (1 in 42) South	2.2% (1 in 45) West	2.8% (1 in 36)
PMC COVID-19 Forecasting Model, Sep 23, 2024
🧵 7/8

Come join our team! I am accepting applicants for the Health Psychology PhD program at Tulane! 🎉

I'd love to work with someone passionate about research, cancer, & Covid safety. Should have a psych/similar background. 😷🧠Tulane University - Health Psychology PhD  Seeking applicants to our PhD program who Understand and are cautious about COVID, Have a background in psychology or a closely-related undergraduate or Master’s degree program, Plan to pursue a research-intensive career spanning multiple scientific disciplines, and Have a desire to help people with serious health conditions like cancer. Learn more: HealthPsychPhD.com or mhoerger@tulane.edu  Small images of a Tulane logo, a cancer ribbon, and a VFlex N95 mask
PMC COVID-19 Forecasting Model, Sep 23, 2024
🧵 8/8

Current state of the COVID-19 pandemic in the U.S.

🔹1.1 million daily COVID infections
🔹1 in 45 actively infectious
🔹High "lull" coming early November
🔹Winter surge to follow

Full dashboard: pmc19.com/dataDashboard has 6 sections, summarized in Tweets 1-6

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More from @michael_hoerger

Feb 26
1) Mardi Gras 2020 was 5 years ago today. ⚜️

It was before the pandemic declaration, before the federal government recommended masking.

COVlD spread quickly through New Orleans, leading to one of the highest mortality rates per capita in the U.S.... Timeline showing Mardi Gras 2020 just 4 days before the first known reported death of C19 in the U.S.  Note. "Peak" diagnoses refers to the peak of the 1st wave.
2) New Orleans service workers were disproportionately hit by the early pandemic. Many died. Many developed #LongCOVID at the time or have now through repeat infections. Many have switched to other sectors....

3) The sad fact is that many service workers are continuing to get #LongCOVID through repeat infections today because the pandemic is ongoing and many restaurants have high occupant density and horrendous air quality....

Read 4 tweets
Feb 17
1) PMC COVlD Dashboard, Feb 17, 2025 (U.S.)

🔥1 in 72 actively infectious
🔥Sustained high transmission
🔥30 states in high/very high transmission (CDC)
🔥3x the transmission of Feb 2021
🔥668,000 daily infections
🔥Only 1 in 28 cases reportedGraph shows 10 waves of the pandemic.  Tables summarized partially in post. Additionally, transmission is higher than during 59% of the pandemic.  How Does Risk Increase with More Social Contacts? Number of People | Chances anyone is infectious 1	1.4% 2	2.8% 3	4.1% 4	5.5% 5	6.8% 6	8.1% 7	9.4% 8	10.6% 9	11.9% 10	13.1% 15	19.0% 20	24.5% 25	29.7% 30	34.4% 35	38.9% 40	43.0% 50	50.5% 75	65.2% 100	75.5% 300	98.5%
2) PMC COVlD Dashboard, Feb 17, 2025 (U.S.)

This is a mid-sized wave, meaning substantial transmission. Notice that transmission remains steady at high rates.

Expect steady or slightly declining transmission, unless the real-time data are retroactively corrected.Two graphs, showing year-over-year transmission and the forecast, summarized in the post.
3) PMC COVlD Dashboard, Feb 17, 2025 (U.S.)

Notice that 30 states remain in high/very high transmission, per CDC categories.

This is the same as last week. Transmission is 3x higher than in Feb 2021, when people were taking more precautions around masking and testing.Transmission heat map and CDC line graph of regional variation in transmission.
Read 5 tweets
Feb 11
1) A lot of high-risk/aware patients I talk to -- mostly getting cancer treatment -- tend to protect themselves from infection by staying home more.

In the work we do, we help patients to understand that a well-fitting high-quality mask can allow them to attend events safely.
2) These are some tips for finding a well-fitting mask among common options in the U.S. and Canada.

3) Here's a more comprehensive diagram of masks that fit most. Aside from #5, these are widely available.

*#5 (Aegle) was the first N95 widely available during the ongoing pandemic for <$1. Hard to find these days, but I gave some to students.
Read 7 tweets
Jan 28
1) PMC COVID Dashboard for the Week of Jan 27, 2025 (U.S.)

🔹1 in 108 actively infectious
🔹3.1 million weekly infections
🔹>150,000 weekly resulting Long Covid conditions Current Levels for Jan 27, 2025 % of the Population Infectious 0.9% (1 in 108) New Daily Infections 443,000  New Weekly Infections 3,101,000  Resulting Weekly Long COVID Cases 155,000 to 620,000  Monthly Forecast Average % of the Population Infectious 0.9% (1 in 106) Average New Daily Infections 452,933 New Infections During the Next Month 13,588,000 Resulting Monthly Long COVID Cases 679,000 to 2,718,000  Running Totals Infections Nationwide in 2025 18,779,000 Average Number of Infections Per Person All-Time, U.S. 3.60  There is more COVID-19 transmission today than during 41.9% of the pan...
2) We predicted the wave peak would be 0.8 to 1.3 million across various forecasts. We presently have it at 0.9-1.0 million, though retroactive corrections can change that. The WHN also runs an excellent model, with a peak estimated at 1.3 million.
whn.global/estimation-of-…
3) Approx 1 million daily infections is quite serious. This is a far cry from the various #nothingburger predictions, and the Monday morning quarterbacks who in hindsight minimize U.S. infections, Long Covid, & disability.

Perhaps they have social media revenue COIs. I don't.
Read 9 tweets
Jan 20
1) PMC COVID-19 Forecast for Jan 20, 2025 (U.S.)

If we are lucky, the 10th wave has peaked, likely in the 0.9-1.1 million daily infections range, barring significant retroactive corrections.

Over the next month, we should still see about 14 million infections, resulting in 700K to 2.8 million new conditions and enduring symptoms under the umbrella of #LongCOVID. This is simply your reminder than transmission remains high on the back on of a wave.

Regarding the peak, there were huge retroactive downward corrections, especially in Oregon. The CDC data originally showed one of the largest waves there all-time, and then corrected it to say a complete lull the whole time. Once the Biobot data get updated, we may see the peak date change by a week, or jump a bit higher than what you see in the main figure.

What you see in the far end of the forecast is unlikely to be a "high lull," but rather an average between a low lull versus a sustained post-peak haunch of lingering transmission. So, keep an eye on the data. If you're putting off a non-urgent medical appointment, we could get into relatively lower transmission in the next 4-8 weeks. What has me concerned is a sneak-peek of @jlerollblues's long-term forecast indicating a clear possibility of an earlier "mid-year" wave than usual, perhaps even in April. We're still getting pretty lucky on the viral evolution front, but the longer that persists, in absent of major policy change, the bigger the wave we could get. It's a very important time to stay tuned.

Caveats: No data from Biobot in weeks (20% model weight). The California wildfires and pending severe storms in the Deep South are wildcards for transmission. School-based transmission could pick up, but to get a higher peak, transmission would need to pick up much faster in the South and West than in the Midwest and North (unlikely).

In the report, I note that PMC will persist even if the CDC drops or scales back their surveillance program. Also, the most two recent "odd" waves have helped clarify how to handle historical data, and a minor update to the model should help with future atypical waves. If time permits, we will fine-tune those changes further, but there are always more battles on the Covid front than we're able to fight. We also provide a link and light commentary on our recent pre-print showing what our current case estimation model for estimating present/prior daily infections has performed well, and why a lot of other models (BNO, JP, CDC) are underestimates.

Info for new readers:

For those unfamiliar with the PMC model, find full weekly reports for the past 1.5 years at pmc19.com/data

The models combine data from IHME, Biobot, and CDC to use wastewater to estimate case levels (r = .93 to .96) and forecast levels the next month based on typical levels for that date and recent patterns of changes in transmission the past 4 weeks.

Our work has been cited in top scientific journals and media outlets, which are fully sourced in a detailed technical appendix at pmc19.com/data/PMC_COVID…

Examples include JAMA Onc, JAMA-NO, BMC Public Health, Time, People, TODAY, the Washington Post, the Institute for New Economic Thinking, Salon, Forbes, the New Republic, Fox, CBS, NBC, and CNN. See pgs 11-13 at the above link.

#MaskUp #VaxUp #CleanTheAir #RapidTestCurrent Levels for Jan 20, 2025 % of the Population Infectious 1.1% (1 in 87) New Daily Infections 547,000  New Weekly Infections 3,829,000  Resulting Weekly Long COVID Cases 191,000 to 766,000  Monthly Forecast Average % of the Population Infectious 1.0% (1 in 102) Average New Daily Infections 466,700 New Infections During the Next Month 14,001,000 Resulting Monthly Long COVID Cases 700,000 to 2,800,000  Running Totals Infections Nationwide in 2025 15,281,000 Average Number of Infections Per Person All-Time, U.S. 3.59  How Does Risk Increase with More Social Contacts? Number of People | Ch...
2) Here is the issue of Oregon I noted, with the "disappearing surge" in the CDC data. By that, I don't mean a surge that declined quickly. I mean, the CDC saying there was a huge surge in OR and then saying it was a lull the whole time. Baffling.

3) It's an important time to reflect that we have never had a federal Covid response commensurate with the magnitude of this $14-billion problem in the U.S.

3/11/20-1/19/21 = 290K infections/day (91 million total)

1/20/21-1/19/25 = 759K infections/day (1.1 billion total)

10 waves and >1 billion estimated infections in 5 years.

We have never had a well-conceived multi-layered mitigation strategy, and the strategy we have had has often underachieved due to insufficient operational management.

This places society at greater systemic risk from repeat-infection Long COVID. The approach is unreasonable to people with primary immunodeficiencies, cancer, organ transplants, kidney disease, type 1 and 2 diabetes, Long COVID, pregnancy, and many other conditions. Upwards of 2 million older adults in the U.S. are in early retirement, with the labor participation rate still well below pre-pandemic levels, and older adults almost wholly accounting for that presently. The children that were pretended to be magically shielded from Covid are not doing well on the cumulative infection front either.

I do not see that changing. I hope the many scientists and public health officials biting their tongues the past 4 years now feel liberated to speak up on Covid. Note that state and regional organizations and individuals were a big reason why transmission was better under control in year 1 of the pandemic.

Note that our statistics are estimated "true" cases based on the PMC model, not reported cases, which are vast undercounts (ascertainment bias). See the first Tweet for info on our model, including our website, which contains hundreds of pages of reports (pmc19.com/data), or read our recent pre-print showing the high accuracy of our case estimation model, to the extent that is ascertainable (researchsquare.com/article/rs-578…). To believe the true infection estimates are lower than these figures, one would have to suspend cognitive reasoning and merely assume transmission happens at vastly lower rates in the U.S. than those documented through the most-rigorous testing-based program in Europe.figure showing the 10 Covid waves (U.S.)
Read 5 tweets
Jan 6
1) PMC COVID-19 Dashboard, Jan 6, 2025 (U.S.)

📈1 in 49 people actively infectious
🔥Nearly 1 million daily infections
🎲About a 50-50 chance someone has COVID in a large class if typical risk and no testing/isolating
🏥300,000+ new Long Covid conditions per week

The infections are likely minor underestimates. AZ and OR did not report this week. They were surging, so the lack of data brings down the average. As well, the model gives 80% weight to CDC wastewater data and 20% weight to Biobot, but Biobot took the week off, so this is dependent on observed changes in the CDC data.

It would be wise to add multiple imputation into the model to account for all the non-random missingness during surges, but I won't likely get to that anytime soon.

The peak is looking more and more like 1.4 million daily infections, but I wouldn't be surprised if it's earlier than shown and more like 1.3 million, based on the pattern of retroactive data corrections last winter. If the real-time data really stink, it could come in closer to 1.0-1.1 million. To top 1.6 million, we would probably need some serious immune escape that at present I just don't see happening. However, in past winters, transmission was declining nationally in early/mid January, and back-to-school is a wild card.

Info for new readers:

For those unfamiliar with the PMC model, find full weekly reports for the past 1.5 years at pmc19.com/data

The models combine data from IHME, Biobot, and CDC to use wastewater to estimate case levels (r = .93 to .96) and forecast levels the next month based on typical levels for that date and recent patterns of changes in transmission the past 4 weeks. Our work has been cited in top scientific journals and media outlets, which are fully sourced in a detailed technical appendix at pmc19.com/data/PMC_COVID…

Examples include JAMA Onc, JAMA-NO, BMC Public Health, Time, People, TODAY, the Washington Post, the Institute for New Economic Thinking, Salon, Forbes, the New Republic, Fox, CBS, NBC, and CNN. See pgs 11-13 at the above link.

We will have a pre-print out in the next week or so documenting very compelling evidence for the validity of using wastewater to estimate case rates. Forecasting is challenging in the context of the current viral evolution, but the real-time estimates of cases are impressively accurate to the best we can evaluate it.

#MaskUp #VaxUp #CleanTheAir #RapidTestCurrent Levels for Jan 6, 2025 % of the Population Infectious 2.1% (1 in 49) New Daily Infections 980,000  New Weekly Infections 6,860,000  Resulting Weekly Long COVID Cases 343,000 to 1,372,000  Monthly Forecast Average % of the Population Infectious 2.7% (1 in 38) Average New Daily Infections 1,272,833 New Infections During the Next Month 38,185,000 Resulting Monthly Long COVID Cases 1,909,000 to 7,637,000  Running Totals Infections Nationwide in 2025 5,468,000 Average Number of Infections Per Person All-Time, U.S. 3.55  How Does Risk Increase with More Social Contacts? Number of people |...
2) PMC COVID-19 Dashboard, Jan 6, 2025 (U.S.)

We're in the 10th wave of the pandemic (1st graph), and transmission this year has picked up atypically late, while coming on strong (2nd graph).Two graphs, summarized in tweet
3) PMC COVID-19 Dashboard, Jan 6, 2025 (U.S.)

Note that sputtering in the West's rise is likely an aberration, as surging OR and AZ did not provide data this week.

Read 5 tweets

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