Confirmed Cases Is an ‘Almost Meaningless’ Metric

It doesn’t matter that the United States surpassed China this week in reported Covid-19 cases because those numbers (83,507 and 81,782 respectively as of March 26) don’t tell us how many people actually became infected in either country. Nor do they tell us how fast the disease is spreading, since only a tiny portion of the population in the United States has been tested.

“The numbers are almost meaningless,” says Steve Goodman, a professor of epidemiology at Stanford University. There’s a huge reservoir of people who have mild cases, and would not likely seek testing, he says. The rate of increase in positive results reflect a mixed-up combination of increased testing rates and spread of the virus.

What should we be watching instead? One possibility is hospitalizations. That idea was put forward by statisticians Jacob Steinhardt, an assistant professor from UC Berkeley, and Steve Yadlowsky, a graduate student at Stanford who specializes in analyzing health care data. They argue that rate of increase in hospitalizations could reflect the growth of the disease without being distorted by changes in the testing rate.

More