Coronavirus, Covid Tracking Project, Covid-19, IHME Model, Institute for Health Metrics and Evaluation, Italy Covid, Johns Hopkins Dashboard, Missouri Covid, New York Covid, Private Testing, South Korea Covid, Testing and Tracing
One big change in recent national Covid trends has to do with testing. In the past week, the number of daily tests has increased by an average of over 50%. That’s shown in the first chart below. Regardless of whether the individuals being tested meet the earlier testing criteria, there are still plenty of people who either want to get tested or are being tested for occupational reasons. Nonetheless, there are reports of unused testing capacity at private labs and universities. Further increases in testing are in the offing, especially if those desiring tests are made aware of their availability.
Increased testing has been accompanied by further declines in the percentage of positive tests. That’s certainly a good thing, but it’s not clear how much of the decline can be attributed to declining transmissions, as opposed to broadened testing criteria.
Coronavirus deaths in the U.S. have also begun to taper. The black line below plots cumulative Covid-attributed deaths the U.S. up through April 28. The red line is the IHME model projection from April 2nd, with upper and lower confidence bounds shown by the blue and green lines, respectively. Despite the notorious broadening of the definition of a Covid death a few weeks ago, the cumulative death toll has remained below the mean IMHE projection.
More bad news is that the number of confirmed coronavirus cases continues to mount. Of course, that is a consequence of broader testing and possibly some arbitrary classifications as well. My previous coronavirus “framing” posts (#1 from March 18th is here, #4 is here ) usually featured a chart like the one below, which shows the number of cumulative confirmed cases of Covid-19 in the U.S. Day 1 in the chart was March 4th, so tonight, April 28th, we’re 55 days in. The blue and green lines are what I originally called “pretty bad” and “very good” outcomes, based on multiples of Italy and South Korea as of March 18th, as a share of their respective populations. Italy’s case count kept climbing after that, but its growth has now slowed considerably.
The U.S. case count has increased dramatically, now exceeding the original “very bad” case curve I plotted in mid-March. Has the U.S. fared as poorly as that seems to suggest? As of April 28, the U.S. has performed about three times as many tests as Italy, and it has identified about 10% fewer cases per capita. If we excluded the state of New York, which accounts for 5.7% of U.S. population but fully 30% of U.S. Covid cases through April 28th, U.S. Covid incidence would be well below Italy’s. However, Italy is still perhaps two weeks ahead of us.
The next chart examines New York’s experience relative to all other states. The blue line is the number of daily confirmed cases in the U.S., and the red line is the U.S. excluding New York state. The vertical gap between the two lines is the daily case count for New York. The fluctuating, slight downward trend in the U.S since about April 10th is largely attributable to improvement in New York. The rest of the country, while not as serious as New York in terms of incidence, is still on a plateau.
The next chart shows daily Covid-attributed deaths for the U.S. (blue), the U.S excluding New York state (red), and New York state (green). The source of this data is the Covid Tracking Project, which reports numbers as of 4 p.m. each day, so it differs from the daily numbers reported by the Johns Hopkins Dashboard. There are a few interesting things to note here. First, New York has accounted for a major share of daily deaths, though its share is diminishing. The decline in New York Covid deaths has been a major positive development over the past few weeks. The pattern of deaths for the U.S. is kind of fascinating: It shows a distinct weekly frequency, with declines over weekends and spikes early in each week. I suspect this is based on the data elements used by the Tracking Project, perhaps based on reporting dates rather than actual times of death. New York does not show that kind of pattern, but I’ve heard that the reporting system there is highly efficient. We might have seen a favorable turn in U.S. daily fatalities over the past week. After the peak early this week, the daily count is likely to decline again over the next few days. We can hope the weekly spikes and valleys reach lower levels as we get into May.
Finally, a couple of charts updating the status of the pandemic in Missouri, my home state. Despite some volatility, new cases continue to taper.
Missouri Covid fatalities are extremely volatile. It’s hard to see the kind of “weekend” phenomenon so apparent in the U.S. aggregate shown earlier. With a couple of recent spikes, it’s difficult to say anything conclusive about the course of daily fatalities based on the chart below. However, as fewer new cases are diagnosed in Missouri, the number of fatalities will follow.
So, what’s the new “framing”? I expect U.S. case counts to continue to climb with more extensive testing. If the most vulnerable individuals remain quarantined or at least carefully distanced, then individuals presenting symptoms will continue to fall, so the rate of new positive will decline. Additions to the case count will come increasingly from the asymptomatic who happen to be tested for occupational reasons, for travel abroad, and ultimately for testing and tracing efforts. Improved light and humidity is likely to cut into the rising case count as June approaches. With any luck it will become negligible along with fatalities. We’ll continue to learn as well. The hope is that a few treatments or even a vaccine will prove out. Test results for a few of the latter might be available as early as September.