The decision to impose school and business closures, travel restrictions and stay-at-home orders to contain Covid-19 is often based on the percentage of tests for the coronavirus that come back positive. But in the U.S., there are no standards for how states report the figure; it’s sometimes calculated using duplicative or irrelevant data; and the meaning of the result is often misconstrued. “It is not a measure of the percentage of the population that is infected or even a measure of the incidence of new cases,” said Jennifer Nuzzo, an associate professor at the Johns Hopkins Bloomberg School of Public Health. “It’s a measure of whether we’re doing enough testing.”A high percentage of positive results suggests other cases remain undiagnosed and additional tests should be conducted to find and isolate infected individuals before they spread the disease further, according to Dr. Nuzzo and other public-health experts. A low percentage is a sign that enough tests have been administered to ensure most infections have been detected and contained, interrupting the chain of transmission.

Source: Wall Street Journal September 04, 2020 09:22 UTC