Tracking the Spread of Active Covid-19 Cases Across the Country

COVID-19 Data Briefs

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We have discontinued our daily collection and analysis of state and county reported data related to the Covid-19 coronavirus. This information is still available from state and local health agencies, national and local media, and the CDC. This change will allow us more time to do what we do best: assisting our clients in solving complex problems with actionable insights that lead to growth. We will periodically present new Coronavirus briefs and reports that further validate scientific findings or when we discover new insights that require further exploration through advanced analytics.

We continue our analysis of Covid-19 data reported by state and local health agencies with a look at Active Cases: the number of cases reported by the state during the prior 14 days.

Active Cases per 100,000 Population

Thanks to the work of scientists around the world, we are learning more each day about the coronavirus. We now have reliable information about the typical length of a Covid-19 infection, which helps us estimate the current number of active cases per state. As we see each state's total of active cases ebb and flow over time, the darker the color of a state equates to a higher number of active cases. This helps us compare the severity of the disease in states in different regions of the country.

In the table below and its appendix, we ranked all 50 states and the District of Columbia by their ratio of active cases per 100,000 population. We also note their highest level (Max) and when that occurred. Eighteen states hit their highest level during the last week of June.

Leading the way was Arizona with 416 active cases rate per 100K population, nearly double the rate for second place (South Carolina). While these rates are severe, they don't come close to the highest rate of 712 active cases per population recorded by New York in mid-April.

Another troublesome example is Florida, currently experiencing a peak period with 196 active cases active per 100,000 people. The severity of this peak is magnified because of Florida's large population (3rd largest in U.S.) and that its population has the 5th oldest median age in the U.S., placing its residents in the above average group at risk for severe cases of Covid-19.

View the entire table of active cases per state's 100,000 population.

Tests per Cases Ratio

One of the striking characteristics of the recent rise in Covid-19 cases is how quickly the country's testing numbers have been outpaced by an increasing number of cases. To illustrate and evaluate current situations, we looked at each state's Tests per Cases (TpC) ratio, which illustrates the extent to which a state's testing program is capturing significant coverage of the state's coronavirus patients.

If a states' TpC ratio decreases even as it administers more tests each day, we know that the number of cases is increasing faster than the number of tests. A low TpC indicates that more tests are needed in order to better understand the spread of the disease with the state. As the TpC approaches 1, it is evident that more people need to be tested.

In the table below, we take a look at the TpC ratio across the U.S. during a recent 16-day period.

Tests per Cases Predicting Future Cases

Another insightful use of the Tests per Cases ratio is to see when the downturn in TpC occurs relative to the spike in reported cases. To illustrate, let's look at the results in two states: Arizona and Florida.

As you see above in the week of May 24, Arizona’s TpC drops significantly (6.75 points) from 25.10 to 18.35 with only a slight uptick in the number of active cases. The following week sees a massive jump in cases from 5,332 to 8,012, despite a similar drop (6.77 points) in the TpC. We see a similar example in Florida.

In Florida there is a precipitous drop of the TpC ratio between the weeks of May 17 and May 24, a decrease of 18.11 points with only a slight increase in active cases (562). The following week of May 31 produces 1,200 new cases and another drop in the TpC of 3.82 points. The last two weeks continue to show large drops in the state's TpC ratio and large increases of active cases.

The correlation between an abrupt drop in TpC and a sharp rise in active cases is shown in many states since the reopening of some states just after Memorial Day weekend. Recently, there have been headlines regarding regional health resources being overwhelmed.

The take-away from these tables is that the TpC ratio remains a significant predictor of future active Covid-19 cases, both in individual states and across the nation as a whole.


Active Cases per 100,00 Population

In the table below, we ranked all 50 states and the District of Columbia by their ratio of active cases per 100,000 population. We also note their highest level (Max) and when that occurred. Eighteen states hit their highest level during the last week of June.

Tests per Cases Ratio by State - Trailing 7 Days

In the table before, we compare the ratio of Tests per Cases during the seven days ending June 24, 2020. Note that the higher the number, the greater the coverage of testing for Covid-19 throughout the entire state. For this data set, we included the calculated ratio for the entire United States as well as the calculated ratio for all 50 states and the District of Columbia.

Stay safe during these times

These statistics reiterate the fact that individuals, especially with underlying health conditions, should continue to shelter at home whenever possible and take extra precautions when in large crowds. Wear a mask, wash your hands often, and continue to monitor the number of Covid-19 cases in your area.

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