Everyone is wading through swamps of virus data

CHICAGO — The latest count of new coronavirus cases was jarring: Some 1,500 virus cases were identified three consecutive days last week in Illinois, and fears of a resurgence in the state even led the Chicago mayor to shut down bars all over town Friday.

But at the same moment, there were other, hopeful data points that seemed to tell a different story entirely. Deaths from the virus statewide are one-tenth what they were at their peak in May. And the positivity rate of new coronavirus tests in Illinois is about half that of neighboring states.

“There are so many numbers flying around,” said Dr. Allison Arwady, commissioner of the Chicago health department. “It’s hard for people to know what’s the most important thing to follow.”

Six months since the first cases were detected in the United States, more people have been infected by far than in any other country, and the daily rundown of national numbers Friday was a reminder of a mounting emergency: more than 73,500 new cases, 1,100 deaths and 939,838 tests, as well as 59,670 people currently hospitalized for the virus.

Americans now have access to an expanding set of data to help them interpret the pandemic, including the percentage of positive tests, the number of people hospitalized and the weekly change in cases. Sophisticated datagathering operations by newspapers, research universities and volunteers have sprung up in response to the pandemic, monitoring and collecting coronavirus metrics around the clock.

For many Americans, the numbers are a way to make sense of the pandemic — which is spreading in the South, West and much of the Midwest but calming in the Northeast — and to gauge whether things are better or worse in their own cities.

They often begin with the case count. That is the daily tally of individuals whose coronavirus infections were confirmed by laboratory tests, a data point that is frequently quoted, misused and debated.

Those numbers are jaw-dropping. In the U.S., the cumulative count of people infected with the coronavirus has surpassed 4 million. New daily records tied to the case count have been alarmingly frequent in recent weeks: On Friday, more than 73,000 new cases were identified across the country, the second highest day of the pandemic.

There are several ways to parse the case count number.

President Donald Trump and other officials have frequently questioned the legitimacy of coronavirus case counts, falsely suggesting that a rise in testing availability is solely responsible for the increase in confirmed infections. More testing can cause an uptick in new reports of infections, but data shows that the rise in cases far outpaces the growth in testing.

Experts suggested that the daily case count is better viewed as a rough measure of whether an outbreak is slowing, expanding or stabilizing.

Another frequently cited number is the positivity rate: the percentage of coronavirus tests that have returned with a positive result.

“The positivity number is one of the first places I go to,” said Ohio Gov. Mike Dewine, who wakes up each morning to a fresh Powerpoint presentation from his staff. “That’s what I zero in on.”

A rising positivity rate can point to an uncontrolled outbreak; it can also indicate that not enough testing is occurring.

Dewine’s daily Powerpoint presentation started small in the early days of the pandemic; it’s now at least 31 slides of numbers, charts and graphs.

He said he also focuses closely on the number of Ohioans who have been hospitalized for the coronavirus, a data point that is difficult to spin or misinterpret. Last week, the pandemic approached an alarming milestone: About as many people in the U.S. are now hospitalized with the coronavirus as at any other time in the pandemic.

“Hospitalization is a hard number,” Dewine said. “There’s no fudge on it.”