The State of COVID-19 in the District

While this is a D.C.-focused post, there are some general issues about COVID-19 that can be gleaned from digging into how D.C. is doing regarding COVID-19 (and it never hurts to look at data!). The good news–very good news–is that, as of Sunday, D.C. had four straight days with no deaths from COVID-19, the longest stretch since mid-March. Hopefully, that trend continues.

The bad news is that D.C.’s prevalence is still too high. As I’ve discussed here, the two-week prevalence of COVID-19 cases (the number of new cases in a two-week period divided by the population of the area you’re interested in) is a reasonable estimate of prevalence, provided there is adequate testing*. For D.C., here’s the two week prevalence by ward and for the whole city:

Ward 1: 0.087%
Ward 2: 0.066%
Ward 3: 0.040%
Ward 4: 0.097%
Ward 5: 0.069%
Ward 6: 0.081%
Ward 7: 0.109%
Ward 8: 0.114%
D.C.: 0.084%

You’ll note that only Ward 3 is below 0.05% percent, and no ward is at 0.01%, which is a low enough prevalence to allow moderately risky activity. Here’s what the two-week prevalence looks like over time–note that the estimates for pre-June data are probably much higher, based on the percent positive rates (likely two-fold or more, especially in March and April):

Picture1

One thing you’ll note is that D.C. on the whole was doing better a couple of weeks ago. The other thing to note is that, compared to June 17, other than the really hard hit wards, which have declined, there hasn’t been much change. Ward 2 has seen an increase in prevalence.

We also can use the ‘German threshold’ of 0.05% prevalence over a week–this is the threshold at which Germany throws the emergency break for a given region:

Picture2

A couple of weeks ago, the entire city, including each ward, was in the clear (if barely). Now the city has edged over the 0.05% threshold and Wards 4, 7, and 8–heavily Black wards–are over the threshold too. Again, this is when Germany starts smashing the big red emergency button, yet all I can detect is complacency.

D.C., which did an amazing job massively slashing prevalence probably from greater than one percent to 0.08% (as mentioned above, in the first figure, the high values should probably be doubled at the least), seems to have eased off. If we want to lower the prevalence such that it would be very unlikely for a school outbreak to occur, then we have to lower prevalence further, probably to 0.01%. Unfortunately, D.C. is trending in the wrong direction.

To return to national patterns, there’s a lot of this going around–we’re releasing too early and not finishing the job, in no small part because of economic considerations and the role of schools as daycare.

Clearly, Arizona and Texas won’t be ready in September, but, even if things level off in D.C., I don’t think we’re there yet either.

*This is also a statistic the European CDC uses, and, in the U.S., when I’m able to find data like surveys of non-COVID-19 patients to hospitals, seems to match up reasonably well.

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2 Responses to The State of COVID-19 in the District

  1. ElHongo says:

    Unfortunately, Germany *doesn’t* start smashing the big red emergency button. Our Conservatives are as abject as yours, and the one thing they don’t run out of is excuses for why they can avoid anti-infection measures.

    The 0.05%/week regulation actually is regulated on State, not Federal level, and many States (especially those with Conservative gov’t) have introduced a cop-out clause.
    Thuringia doesn’t; they mandate an evaluation whether further restrictions are necessary at 0.035%/week already, and require further restrictions at the 0.05% threshold.
    NRW, where the latest superspreading happened, has such a clause, stating that in localized outbreaks, restrictions may be applied to the sources only. That, of course, is entirely useless to prevent superspreading events from taking hold in the general population (given that German testing practice is still so haphazard that usually, we know who got infected only 2 weeks after the infection occurred, and up to a week after they started to infect others). As I write, half of NRW has a worrying rate of new infections (still only ~0.01%/week, but rising, and spread over a large area including most of the major cities). And regardless, the Conservative-Liberal State government is permitting private indoor events of up to 150 people, and public indoor events of up to 300 people, starting this Wednesday. Most risky, the requirement to provide basic hygiene measures if you want to host a public event has also been shelved. So every disco can re-open, provided they don’t let more than 300 people inside at any time, and label it as a special event, and do a token effort that everyone wears a mask and keeps a distance.

    You may wanna look at the system they have in Berlin tho – it takes a 3-factor approach (R value, 7-day prevalence, EMC beds). For all I can say, Berlin – though it has a good share of cases – has so far gotten off lightly, despite being a metropolis of 5 million, having a large population of sans papiers and transients and non-German speakers, having cramped living conditions, and having a vigorous pro-virus community who love to protest MAGA style without regard for their or other peoples’ safety. Remarkably, Berlin has hitherto largely prevented the virus from spreading to the poorer neighborhoods. As of now, Berlin’s 7-day incidence is 0.008%/100K, and already the administration is getting ready to act, because the value, as well as the R value, are on the rise.
    The Berlin State govt (which includes neither Liberals nor Conservatives nor neofascists) argues – correctly, as far as this biologist is concerned – that a “prevalence per n inhabitants” rule is insufficient: it does not take into account the fact that a pathogen’s spread is more dependent on host *density* than on *overall* host population *per administrative division* (pathogens don’t respect administrative boundaries after all). So they do well to include both a second semi-independent measure of infection spread (the R value), as well as a measure of the consequences (EMC load). Oh, and their incidence cutoff value is 0.03%/week, with the alert phase starting at 0.02%/wk already. And they mandate further restrictions if 2 of the 3 indicators are above the critical threshold, with measures to be prepared as soon as 2 indicators go above the warning threshold.
    Unfortunately, they do not seem to provide these rules in English; the German data of today, with the tresholds, is here: https://www.berlin.de/sen/gpg/service/presse/2020/pressemitteilung.948468.php, and the time-series data are here: https://www.berlin.de/sen/gpg/_assets/service/pressestelle/2020/juni/sengpg-pandemieindikatoren-20200621.pdf
    Note the usefulness of the R value as an indicator; it’s the first warning sign, and when this indicator turns critical, the public is warned and apparently most people have so far heeded these warnings.
    (Note that the R value is above the critical threshold today, but only since yesterday – the alert gets triggered only after 3 successive days of R>1 to avoid the weekend effect)
    It seemed a bit complicated at first, but seeing what happened in Paris, Madrid, Milan, NYC, etc etc etc, it worked quite smoothly so far; one hopes it will continue to do so. At present, one can only conclude that any metropolis in the world is not ill-advised by any means to install a similar multi-indicator system rather than relying on mere 7-day incidence alone. Because that value may, at high population densities, only turn critical when it is already too late.

  2. ElHongo says:

    Addendum: it is not quite clear why exactly the NRW incidence has risen markedly. It may be related to the superspreading at Gütersloh, but AFAICT it already started earlier (slowly and almost imperceptibly at first, but one does develop an eye for population dynamics in this line of work).
    In some places, it probably was the pro-virus protests (we call them “hyena demos”, as a pun on “hygiene”) that kicked it off. Elsewhere, it was almost certainly partygoers who assembled in the cramped inner cities by the 100s, sometimes 1000s.

    This is worrying, because it suggests (in line of the Wisconsin MAGA demo superspreading) that outdoor locations may not be as safe as commonly assumed. The outdoors may be safe enough IF the location is exposed to sun and wind, and IF there actually is wind. But if it is hemmed in between buildings, it may effectively be almost as unsafe as a badly ventilated room.

    Stay safe.

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