As Coronavirus Cases Fall, Countries Struggle to Measure When It’s Safe to Reopen

In Europe, as the rate of new coronavirus infections slows, governments are reconsidering how best to measure disease progress and guide their decisions to ease their confinement. Germany, France, Spain, Italy and other hard-hit countries have seen new cases drop to about 1,000 a day and are starting to reopen their economies. Some scientists expect that number to stabilize around that level, allowing hospitals to cope with an influx of patients for the foreseeable future.

When the German states ordered a nationwide lockdown, chancellor Angela Merkel pointed to the remarkable reproduction figure, or R, which measures how many people on average are infected with the disease by a person infected with the coronavirus. As long as the R value remains above one (the average infected person will infect more than one), the disease will grow exponentially, threatening the ability of the country's health care system to cope with severe cases. However, if it falls below 1, it will fail.

R is calculated differently in different countries/regions. In Germany, it was established by dividing the number of infections in the first four days by the number of infections in the previous four days. The index was 0.81 on Wednesday, according to the Robert Koch Institute, which tracks the course of the pandemic in the country. The Italian government has been making regional and national estimates of R, and its stated goal is to keep the value of R below 1. French authorities downplay the total number of confirmed cases because testing focuses on people with symptoms, and France does not have the capacity to test large Numbers of asymptomatic people. Smaller countries such as Belgium, the Netherlands and Luxembourg have not yet used R for disease control, focusing instead on a number of daily indicators, such as the number of new infections, the occupation of intensive care units, deaths and hospitalizations. The UK has put R at the center of its relaxed locking strategy, but it also relies on monitoring the number of people infected.

Source: https://www.wsj.com/articles/as-coronavirus-cases-fall-countries-struggle-to-measure-when-its-safe-to-reopen-11589403732?mod=hp_lead_pos9