Chester County Case Count

(for those wondering why this is on a martial arts website – here’s what I do in my other job)

I’ve been waiting for weeks to write this both because of time (we were near the end of the semester at Penn State), but also because we just didn’t have enough information yet about the newest COVID variant. While it is probably prudent to be safe rather than sorry, many of us have put our lives on hold for the better part of a year and a half, and are not looking forward to returning to our hermitages.

Winter is Coming

As I write this, the rate of COVID infections in Chester County are as high as they have ever been. The seven-day county transmission level has been rated as very high, and we know that the Omicron variant is out there. In fact, the case rate per 100k is as high as it has been in the pandemic thus far.

Right now, most of the high spread here is due to Delta since the Omicron variant was only first detected in PA on December 3rd, but the rate of Omicron infections is rising quickly. Whereas the doubling rate for infections for Delta is approximately two weeks, the Omicron doubling time for infections is estimated to be between two and three days.

The difference in case numbers in these scenarios, which all start from a single infected individual, is substantial. For three day transmission, after 14 days, there are on average two Delta cases (red), about 25 Omicron cases (3 day doubling time), and about 128 Omicron cases (2 day doubling time). Some sources estimate that the doubling time for Omicron is 1.5 days, which if true, only pushes the number of infections higher.

Note that these estimates are based on real world data tracking infections, not hypotheticals or what if scenarios in models. That said, it’s possible that these are still underestimates for a number of reasons. Generally, if one is vaccinated, the chance of asymptomatic infection, or mild infection is relatively low compared to the non-vaccinated, and as such, not all those who have Omicron will get tested. That runny nose you have, which you usually have every winter, might actually be Omicron. But the difference this time, is that your runny nose could infect someone in your vicinity who, unlike you, is not going to get a mild case and may be hospitalized or who may die.

The jury is still out for the severity. The media have been cherry picking stories to try to convince people that Omicron is not that severe. Often these include the numbers from the hospitalizations in Gauteng Province, South Africa where Omicron was first identified. So based on the reduced rate of hospitalizations there (about 29%) many pundits have concluded it’s less severe. Let’s apply that math to our graphs from above. For Delta, the hospitalization rate in England in Spring of 2021 was 2.3% of patients. Thirty percent (rounded up from 29%) fewer hospitalizations means that 1.6% of our cases will be hospitalized. So let’s scale our case graphs by those numbers and see what happens.

Ooof! So if Omicron doubling times are every 2 days, by day 30, there will be many times the patients hospitalized than for Delta. If it’s a three day doubling time, it’s a bit better – but still not good – still up by a factor of 161 by the end of a month. Now to be clear, we started with a single infected person at day 0, so at the end of 30 days, there still isn’t yet a “full” patient for the Delta case. But this highlights just how much more severe the Omicron scenario could be.

That said, it’s really not yet clear that these lower hospitalization rates will hold and as they say, the night is still young. A study from Imperial College in London has indicated that there is NO evidence of reduced severity in Omicron cases.

Vaccinations help, right?

But wait! You’re vaccinated, so why worry? We already said that those who are vaccinated fare better than those who aren’t and will have a less severe reaction. There are two main reasons: first is because you come into contact with other more vulnerable individuals who might get it worse than you, and second, because your immunity is waning with time. The graph below shows increasing numbers of severe cases, the farther out one is from the second shot with Pfizer/BioNTech or Moderna, or the first shot with Janseen.

Of 371 patients admitted for SARS-COVID-2 infection between August 4th and October 12th, 2021 in New Haven, CT, 82 (or 22%) of them had breakthrough infections. The graph below shows the breakdown of treatments amongst this group. Those requiring only supplemental oxygen were the least severe. However, 25 of the 82 (30.4%) of those with breakthrough cases had more severe presentation.

What about Masking?

Considering these data, what’s to be done? Improved masking is certainly recommended. Whereas the typical cloth mask will mostly help protect others from the wearer, an N95 or equivalent mask can help protect YOU from others. This is because cloth and even surgical masks will often have gapping where particles can flow in via the path of least resistance (more on this below). When you breath or sneeze out with such a mask, most of your outgoing aerosols will be caught in the mask. However, when you wear an N95 equivalent, because such masks have a good seal if worn properly, both incoming and outgoing air is filtered to a greater extent. N95 masks have been found to have 95% efficiency for particles as small as 0.1-0.3 microns. The following graph from a recent study of mask filtration efficiency shows how well various masks work.

Source

For comparison, here is the graph published by the New York Time’s Wirecutter with data on common commercially available masks from Colorado State University’s Center for Energy Development and Health. For those of you who don’t do unit conversions as frequently, a micromenter (μm) or micron is 1000 nanometers (nm), so the 1 micron level on the graph below corresponds to the 1000 nm level on the graph above. For reference, the minimum size of a COVID-19 carrying particle in the air is thought to be about 4.7 microns.

Interestingly, a large number of the masks shown in the below graph filter fairly effectively at the 5 micron level. The key difference between these and an N95 is the facial seal. If you cannot get one of the commercial masks to fit your face well, you should go with the N95s or KN95s to prevent inflow due to gapping. But the other difference is reusability. The CDC only recommends reusing N95 masks up to 5 times. However, in terms of fit and seal, there is evidence that such masks may be reused up to 40 times. This is subject to the usual caveats of protecting the outer surface of the mask from contamination and letting the masks “rest” for 5 days in between uses. Considering that some of the effective cloth masks from below can be washed more than a hundred times without losing significant filtration ability, it is probably more cost effective and environmentally effective to go with cloth – IF you have a good fit, since the point of all this is not getting sick, or spreading virus if you are sick.

One last word on masks, and that has to do with fit. A poorly fitting mask may let many virus particles escape or enter, and this has recently gotten onto the CDC’s radar. They are now defining a leakage ratio as the ratio of particles that are incident on the mask compared to the number that make it through via any path. Therefore, the higher the leakage ratio, the more particles that are stopped, and the better the rating. Masks with a ratio of 5 and higher get an official “Workplace Performance” rating, and those with a ratio of 10 and higher get the “Workplace Performance Plus” rating. The performance of cloth type masks in this respect are largely unknown. However, there was a June 2021 paper from the University of California, Davis, that addressed this point with respect to surgical masks which demonstrated that most leakage in such masks, even when fitted, came out around the top. Their measurements suggest that the leakage ratio may be in the vicinity of 2, meaning as much as half of the air escapes around the top or sides. However, for some of the individuals measured, it seemed that the leakage ratio could be as high as 10. In short, it probably depended on facial structure as much as anything else. Masks such as the Enro models are in terms of fit, perhaps a little better than a well fitted surgical mask. I was curious if Enro had made any such measures, so I sent a query to Enro to ask about this, but at the time of writing had not heard back. In an attempt to prevent fogging of glasses, some medical professionals have started using surgical tape to tape their masks to their faces, and evaluations of this for the reduction of particle counts seem to suggest that this makes a significant difference. Such a strategy may also reduce the need to adjust ones mask, although I can’t speak for the comfort of doing this.

Face Shields?

Given the transmissibility of Omicron, one must also ask about wearing face shields as this may decrease the risk of picking up COVID via the eyes which are also mucus membranes. In the hospital where I do research, we are required to wear face shields if within 6 feet of a patient (in addition to masking). How well does this work? The idea is that the face shield provides a barrier to the direct flow of particulates and aerosols. For example, if someone were to sneeze or breathe in your direction, the particle flow is directional, the face shield serves as a wind break to deflect the particles. Some work on the efficacy of face shields has been done with one paper indicating that their usage reduces risk by a factor of three. Of course, their efficacy is situational. In aerosol tesing in rooms where a virus has had time to disperse, it was found that face shields were less effective and may only decrease risk by 23%. In a well ventilated room where people are maintaining social distancing, it’s not immediately clear how much more protection face shields will offer.

Moving Forward

Given all this, our strategy at OpenSource Wushu over the upcoming weeks will be to use enhanced masking (well fitting N95 or equivalent filtration), enhanced ventilation (keeping the door and windows open in addition to the HVAC system), and social distancing (staff applications rather than qin-na, push-hands, and hand to hand). Likewise, I would recommend that all participants who can get boosted do so. The University of Delaware is taking the Omicron variant seriously and requiring all students to be boosted to return in the Spring for either in person OR online classes as all students have campus access. It is possible that we may follow this trend in January and mandate boosting for those eligible for in class attendance.

I hope all of you stay safe over the holidays, and wish you the best!
Sifu Tim Niiler

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