Officials often use similar words when describing the pandemic, but they are not always talking about the same thing, making global comparisons less useful.
Making sense of the coronavirus pandemic requires getting up to speed on semantics as much as epidemiology.
Government officials and health care professionals toss off mentions of mortality rates, flattening the curve and lockdowns, assuming that we know what they mean. But the terms mean different things from country to country, state to state, even city to city and person to person.
Officials use the same phrases about mass testing, caseloads and deaths to describe very different situations. That makes it hard to give clear answers to vital questions: How bad are things? Where are they headed?
People search for insight by comparing their countries to those that are further along in the epidemic. But if the terms are misleading or used in differing ways, the comparisons are flawed. Also, the statistics and vocabulary offer a false sense of precision while in reality, the information we have shows only a fraction of what’s going on.
“The new cases or deaths each day are given as exact numbers, and we’re trained to take that at face value,” said Mark N. Lurie, an epidemiologist at Brown University’s School of Public Health. “But those are far from exact, they’re deeply flawed, and their meaning varies from place to place and from time period to time period.”
The United States recently hit an attention-getting milestone, passing China as the country with the most reported infections. But there is deep uncertainty about whether there really are more American cases, and about how well the figures reflect reality.
Countries vary wildly in testing for the virus and how they report the numbers, and experts say most infections are going undetected. So the publicized national tallies are rough, incomplete pictures that may not be all that comparable.
And that’s if countries are forthcoming about their data.
Officials in the United States say that China, which has reported more than 82,000 infections, has understated its epidemic. Until this week, the Chinese government excluded those patients who tested positive for the virus but had no symptoms.