This is the second post comparing Massachusetts’ Covid statistics to other states, but with a focus on cases. I’m using the daily historical data from the Covid Tracking Project (CTP) to perform calculations, but used the New York Times and Worldometers databases to check figures from the CTP.
|Table 1: Largest Case Discrepancies Among Data Aggregators|
|Data through October 28, 2020|
|2nd Largest||New York||4.6%||Wyoming||10.0%||Wyoming||10.0%|
Table 1 summarizes the discrepancies between the three data aggregators for case data through October 28th. The entries in the tables are the percentage difference in the case totals to date for each pair of aggregators. As with deaths, the best agreement was between the New York Times and Worldometers, and the CTP differed more from the other two aggregators.
In the first post in this series, I defined three phases to the pandemic (Spring – ending May 28th, Summer – ending September 12th, and Fall – ongoing) based on peaks and troughs in national case data from the New York Times. Table 2 shows the case rates and rank for Massachusetts as well as the top-ranked and bottom-ranked states (including Washington D.C.) for each phase of the pandemic. (The W in the Massachusetts rankings stands for Worst).
|Table 2: Case Rates per 100000 and Rank By Pandemic Phase|
|March 1 through October 28, 2020|
|MA||34th W||2,184||4th W||1,377||46th W||430||40th W||378|
Table 2 clearly shows how the geographic concentration of the pandemic has shifted over time. The Northeast had the most per capita cases in the spring; the Southeast and Southwest in the summer; and parts of the Upper Midwest, Rocky Mountain, and Great Plains states in the fall. In fact, the Northeastern states generally had the lowest case rates in the summer and fall – only Hawaii in the fall broke the Northeast’s monopoly on the lowest five case rates. Massachusetts fits this pattern as well, even if its case rate is not among the five best.
The table also indicates how per capita case rates have increased after the spring, even though death rates were much higher in that period. The spring 7 day average national peak was almost 32,000 cases per day, compared to almost 67,000 cases in the summer and 78,000 cases now. Some of this increase is because more testing is being done now than in the spring, resulting in more cases being diagnosed.
In Massachusetts, for example, the average daily number of tests more than doubled from the spring (starting on March 15th) to the summer, and then almost tripled from the summer into fall. However, much of that summer to fall increase has been driven by higher education testing, which now accounts for about half of all testing in the state. Nonetheless, the increase is significant.
These statistics, when compared to the death rate findings in the prior post, point out one of the central puzzles with covid in Massachusetts. Massachusetts is among the states with the lowest number of per capita cases, especially after the spring, but among the states with the highest number of per capita deaths overall, and higher than one would expect in either the summer or fall.
Why? The obvious answer is the case fatality rate (CFR) – the percentage of cases that lead to death. To look at CFRs across states, I compared case rates through the end of the spring and summer phases to deaths rates through the end of the corresponding trough in deaths. For example, I looked at case totals through May 28th in each state, and compared them with deaths through July 5th (from Table 1 in the prior post that defines the phases). Implicitly, I’m assuming about a five week time lag between diagnosis and death. Since the fall phase is still underway, I only performed this analysis for the spring and summer.
Because I’m using about a five week time lag, I may be overstating the CFR for the two phases. Nonetheless, this exercise does provide insight into the Massachusetts conundrum. Table 3 summarizes the results. Death data is only through October 16, as that is the trough in deaths from the summer phase.
|Table 3: Case Fatality Rates and Rank By Pandemic Phase|
|March 1 through October 16, 2020|
|MA||3rd W|| 7.8%
||7th W||8.6%||1st W||5.1%|
The use of a five week lag in deaths does seem to jumble some of the reporting. For example, Arizona has the second highest CFR during the spring. This is almost certainly because some deaths from the summer phase are paired with cases from the spring phase when Arizona had a relatively low case rate.
The table shows the dramatic reduction in CFRs from the spring to the summer. Outside of the Massachusetts outlier, the worst CFRs in the summer aren’t much higher than the best CFRs from the spring. There are likely several reasons for this. As noted before, increased testing has presumably led to the identification of less ill patients. Second, the average age of people diagnosed with Covid has decreased. Finally treatment protocols have gotten better (https://www.nytimes.com/2020/10/29/health/Covid-survival-rates.html)
However, a very surprising result is the out-sized Massachusetts’ CFR in the summer, significantly higher than any other state. Not all of this can be explained by the death lag improperly assigning cases and deaths to the wrong phase. Even as Massachusetts’ relative case rate has come down, its death rate has stayed relatively high. Is this the long-term care issue again?
To check this, I performed the same hypothetical as in the prior post. What if the percentage of deaths from long-term care facilities in Massachusetts were 40% instead of 70%? In that case, Massachusetts’ overall CFR for the spring and summer would have dropped to 4.6%, ranking it 8th highest overall instead of 3rd. Similarly, the state would have improved only to the 5th worst CFR in the summer period. Some improvement, but the state is still a laggard. There is something else going on.