Chesterton Tribune



Porter County C19 test positivity rate climbing

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Test-positivity has become a crucial datapoint in tracking a community’s success or failure in containing the COVID-19 pandemic.

Test-positivity is a simple enough ratio: the percentage of people who test positive for COVID-19, out of the total number of people tested. Simple as it is, though, test-positivity has proved to be a key measure of a community’s response to COVID-19, both in terms of the community’s testing infrastructure and its efforts to check the contagion.

Thus, in the early days of the pandemic, when testing supplies and facilities were limited to the point of being rationed, the national test-positivity rate was approximately 20 percent. That is, out of every five people tested for COVID-19, one tested positive. It certainly wasn’t the case, in March and April, that one out of every five people in the country was infected, but that only those with the highest probability of having been infected--the sickest, the most symptomatic--were even able to secure a doctor’s order for a test. Those presenting minor flu-like symptoms were typically sent away, in the hope that they only had the flu. Test-positivity, in other words, is an excellent indicator of the penetration and availability of testing within a community: the lower the rate, the more people a community is managing to test.

But also, over time: the lower the rate, the fewer sick people there are seeking testing, a strong indication that the overall number of new cases in a community is falling.

As a benchmark, the CDC’s guidance on re-opening, issued on May 14, recommended a test-positivity rate in a given community of under 10 percent among symptomatic, asymptomatic, and presymptomatic persons. The World Health Organization’s guidance, issued on May 12, recommended an even lower rate: 5 percent or less for at least 14 days.

Put those benchmarks in perspective. On May 5--the day after the State of Indiana officially began its phased-in re-opening--Porter County’s test-positivity rate was 14.9 percent, well above both WHO’s benchmark and the CDC’s, but well below Indiana’s rate (18 percent); Lake County’s (20.8 percent); and LaPorte County’s (17.2 percent).

Five weeks later, as of Tuesday, July 14, Porter County’s test-positivity rate has nearly halved, falling to 7.8 percent, well within the CDC’s guidance. Indiana’s, in the meantime, has fallen to 9.1 percent; Lake County’s to 12.2 percent; and LaPorte County’s to 7.4 percent, nearly half a point lower actually than Porter County’s.

However, a biweekly calculation of Porter County’s test-positivity rate since May 5 points to a disconcerting trend beginning in mid-June:

-- Between May 6-19, the test-positivity rate dropped to 11 percent from 14.9 percent.

-- Between May 22-June 2, the rate dropped to 8.1 percent.

-- Between June 3-16, the rate plunged to 3 percent.

-- Then, between June 17-30, the rate inched a full point higher, to 4 percent.

-- And, in the last two weeks, July 1-14, it’s more than doubled, to 9.2 percent.

That sharply upward trend in Porter County’s test-positivity rate coincides with a surge in new cases since mid-June, over the course of which in just four weeks a 10-week low of 25 new cases (the week ending June 13) swelled to an all-time high of 99 new cases (the week ending July 11), with a total of 254 new cases over that time.

There is one thing, on the other hand, which the upward trend in the test-positivity rate does not coincide with: an increasing number of tests conducted over those four weeks.

In fact, just the opposite:

-- In the seven-day period June 17-23, the Health Department reported 1,369 tests, an average of 196 per day.

-- In the period June 24-30: 1,382 tests, an average of 197 per day.

-- In the period July 1-7: 1,055 tests, an average of 151 per day.

-- In the period July 8-14: 1,043 tests, an average of 149 per day.

In other words, over the same four-week period in which each week saw a higher number of new cases than the previous one--35, 51, 69, and 99--the average number of tests conducted per day in the first half of the period, June 17-30, plummeted by 24 percent in the second half, July 1-14: from 196.5 to 150.

Those 254 new cases are not, accordingly, an artifact of increased testing but in fact evidence of a resurgence of COVID-19 in Porter County, as the spike in the test-positivity rate indicates.

As the Chesterton Tribune has been making consistent note of, those 254 new cases since June 13 have been accompanied neither by an increase in hospitalizations nor by an uptick in deaths. Since June 16 no more than four patients have been hospitalized on any given day in Porter County (compared to a high of 28 hospitalizations on May 20); and only two deaths have been recorded since June 22 (compared to a one-week high of six in the week ending June 6).

The demographics of these new cases suggest why: the overwhelming majority of the newly infected are young people under 50, most of them under 40. These people are less likely to be hospitalized with COVID-19, less likely to become gravely ill, and far less likely to succumb to their sickness.

But hospitalizations and deaths tend to lag behind new cases by two to four weeks. If, by August, hospitalizations remain low here and no or few additional deaths have been reported, it will mean that Porter County’s most vulnerable population--older folks with pre-existing conditions and co-morbidity factors--have managed to avoid being infected by their children and grandchildren.



Posted 7/16/2020




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