What we’ve learned, six months in
CORONAVIRUS IN MARYLAND
About six months ago, the first two Marylanders succumbed to the coronavirus. The state’s virus-related death toll has mounted since to nearly 4,000.
More than 120,000 residents have been infected with COVID-19, the illness caused by the virus, with 15,000 of them requiring a hospitalization. Some of them never walked out.
After spending half of 2020 facing a pandemic, here’s what we’ve learned.
New cases
From the first three cases confirmed March 5 to the 613 reported Saturday, the state has averaged about 600 new known infections daily.
Over the past two weeks, the average count of daily cases has been around that mark, and the same was true in mid-April.
But 600 daily cases in April and the 600 daily cases in September don’t necessarily represent the same thing. Both the number of tests performed and the percentage of tests that return a positive result have shifted significantly over that time.
Many more tests are being performed — screening more of the population— and the rate of infection has plummeted.
Percentage of positive tests to total tests performed, first two weeks of the month:
April: 22.0% of 44,261 May: 19.7% of 78,456
June: 7.0% of 143,434
July: 4.5% of 193,268
August: 3.6% of 345,205 September: 3.6% of 292,949
Positivity rates
The past six months have brought the term “positivity rate” to the forefront. It measures the percentage of virus tests that return a positive result. Or does it represent the percentage of people who get tested and are confirmed to have the virus? Or is it tracking something else entirely?
It depends on who you’re asking and what state you’re in. As Dr. Jennifer Nuzzo, lead epidemiologist for the Testing Insights Initiative at John Hopkins University’s coronavirus resource center, explained, there’s no federal standard for measuring positivity rate in terms of calculating it by tests or by people, or even what types of tests should be included.
Maryland calculates its seven-day positivity rates as the percentage of all diagnostic tests performed that come back positive. Hopkins, in determining rates for Maryland, the other 49 states, Washington D.C. and Puerto Rico, looks at the rate at which people tested for the first time have a confirmed infection.
Often, people get tested multiple times, possibly to ensure they still don’t have the virus, to confirm a positive diagnosis or to see whether they’ve recovered from an infection. As long as those repeat tests don’t occur at the same place at the same time, they get included in Maryland’s calculation. Hopkins includes only the first test, unless a person who previously tested negative then tests positive.
The difference in methodology results in a wide gap. For example, when Maryland reported a positivity rate Sept. 15 of 3.42%, Hopkins had the state at 6.40%. The World Health Organization’s recommendation for easing virusrelated restrictions is two straight weeks with a positivity rate below 5%. On Thursday, the Hopkins-calculated rate joined Maryland’s under 5%.
But even though both Hopkins and the state refer to what they’re calculating as positivity rate, they’re measuring different things.
For example, say you get tested five times in a week, and all five of your tests come back negative. Your coworker also got tested five times, but one of his tests came back positive. Of the 10 tests taken, 10% came back positive; that’s how the state gets its positivity rate. But of the two of you, 50% got at least one positive result, and that’s how Hopkins’ positivity rate is determined. Same situation, different use of data; same term, different result.
States have used positivity rate as a benchmark to determine whether visitors from other states are required to quarantine upon arrival, a practice Nuzzo cautioned against as a misuse of the datepoint.
If it takes a 5% or lower positivity rate to avoid travel restrictions, and a state says it meets that but Hopkins doesn’t, what’s the proper judgment? Six months in, and the answer remains unclear.
Impact varies
When Maryland first began identifying the dead and infected by race in early April, Black residents accounted for about half of both the caseload and death toll, among those whose race was known. On the same day, those older than 60 represented 30% of the infections but more than 80% of the fatalities.
Those percentages have shifted over time, but the point remains true: The virus disproportionately affects Maryland’s older and Black residents.
About 23% of Maryland’s residents are 60 or older, according to U.S. census data, but 87% of the virus’ victims in the state have been in that age range.
Nearly 57% of all the deaths have been among nursing home residents and staff.
Black residents account for 41% of the people killed by the virus whose race was known even though they make up 31% of Maryland’s population.
In recent months, older residents have represented a significantly smaller proportion of the cases but nearly as large a proportion of deaths.
The percentage of the caseload represented by Black residents has increased while their share in the death toll has declined slightly, but both remain above their representation in Maryland’s overall population.