In the last two weeks (ending November 7), US COVID stats have been driven by a major outbreak in the north central part of the country, especially in the upper Mississippi River watershed. Wisconsin and Illinois have been hardest hit. In most of the rest of the country, there has been a modest increase in the spread of the infection. These are New York Times maps of the outbreak nationally near the beginning and the end of this two-week period. They show the degree to which the outbreak is concentrated along the upper Mississippi River watershed and how it has spread over the last two weeks.
The number of COVID patients hospitalized in the US increased during the last two weeks by over 30%, ending the two-week period above 55,000, and appears to be set to challenge the two previous peaks of 60,000 in April and July. ICU bed and ventilator usage also increased by approximately 30%.
Average daily fatalities also increased, moving from 750 in the previous two-week period to 867 over the last two weeks. However, fatalities were more rapidly accelerating toward the end of the two weeks.
The 30-day lagging fatality rate continues to hover around 2%. The key question is whether that ratio holds in the face of the large surge in new cases or begins to decline again. Clearly, the IHME model believes the ratio will hold. IHME slightly raised its year-end fatality estimate to 326,000, which would require the current daily fatalities to double over the next seven weeks. I continue to be skeptical and think it is more likely that we will begin to see a decline in the case fatality rate as we are seeing clear signs of a divergence of the increase in positive testing results and serious disease outcomes. But either way, we will know soon enough.
US testing continued to increase, averaging approximately 1.25 million tests per day for the last two weeks, a 20% increase. But the number of new positive cases jumped by even more, 61,000→91,000 (+49%). The ratio of tests coming back with a positive result moved up from 5.8% to 7.3%. So, while perhaps about 40% of the new positive results can be explained by increased testing, about 60% is likely due to a more rapid spread of the virus.
Many are referring to the current outbreak as the third wave of the pandemic in the US. Certainly, looking at the country as a whole, that is true. But what actually has occurred is that three different regions of the country have gone through one surge at different times. The first was the northeast in the spring and the second was the sunbelt over the summer. Now it is the north central.
The first two peaks left residual level infection in those communities which has grown modestly as restrictions have been eased. If the current outbreak follows the pattern of the first two, we should see it begin to ease over the next few weeks. At that time almost the entire country will have seen a large surge in infection. The question is whether the pattern of a lower level of background infection continues or whether we start seeing new surges in areas that were previously hit. Let’s hope that the pattern of one surge holds.