During the early stages of the pandemic, the big story in the United States was testing: The federal government’s initial failure to produce a working test and scale up its production meant that the country struggled for months to keep up with the virus’s spread. In May, the Harvard Global Health Institute estimated that the U.S. needed to perform 1 million tests a day to contain the outbreak by identifying cases before they spread, a mark we didn’t surpass until late September. After that, testing finally picked up speed: By late November, the seven-day daily-testing average had jumped to more than 1.8 million.
But lately, daily tests have plateaued. After nearly breaking the 2 million mark in mid-January, daily tests today remain stuck at about 1.8 million. The stall-out is a mix of good and bad news: Although more testing would give us a clearer view of the outbreak, lower testing numbers reflect a pandemic in retreat, as demand for testing tends to rise with the spread of the virus.
Much of the data we have about the pandemic are messy, but that is especially true with testing. The numbers of tests that are used, and the results of those tests, are disrupted by weekends and holidays, and the results of many rapid tests aren’t reported at all. Even though the testing information is jittery, we can still see how it fluctuates with the coronavirus’s spread by comparing it with the number of COVID-19 hospitalizations, which is the most reliable pandemic metric we have. U.S. hospitalizations peaked three times, corresponding with the pandemic’s three surges. Nationwide testing trends paint a somewhat different picture—hospitalizations peaked in April but testing didn’t, because the U.S. was struggling with its testing—but there is still a clear pattern. Here’s what the two metrics look like plotted together.
Around Thanksgiving, there was a major dip in testing, which was likely a combination of a bump in demand before the holiday, a drop-off in demand right after, and a lag in states’ reporting their data. A similar pattern occurred around Christmas. But taken as a whole, the numbers suggest that when pandemic conditions have worsened, the demand for testing has increased.
It’s a fairly rational response. “In the beginning [of a surge], people are starting to get tested because they're getting sick more often,” Emily Landon, an infectious-disease expert at the University of Chicago, says. “Then people are seeing that other people are sick more often, and they're like, ‘Maybe I'm getting COVID too, and I need to get tested.’ And there’s this general awareness in the community, as you start seeing more news reports that people are getting tested.”
The pattern between tests and hospitalizations holds at the regional level as well. Here’s the South, for example:
The spread of the virus is obviously not the sole driver of testing. For instance, all regions saw a steady rise in testing in September, even though conditions were dramatically worsening only in the Midwest, because supply increased throughout late summer and early fall. At other moments, particularly in the spring, many people who wanted a test could not get one, because of supply-chain limitations. When the American Society for Microbiology started surveying laboratories about testing capacity and supply shortages in September, the organization found that more than 80 percent of labs reported testing-kit shortages. That number now hovers just under 60 percent.
Apart from the ebb and flow of hospitalization numbers, another data point also supports the idea that testing is highly related to the state of the pandemic: The demand for tests seems to closely track Americans’ sense of how at risk they are at a certain point in time. Since mid-March 2020, the University of Southern California Dornsife has been maintaining a robust COVID-19 poll, which includes a question about risk perception:
In early June, respondents estimated that they had about a 20 percent chance of getting COVID-19. That reached a summer peak of nearly 25 percent in late July, which corresponded to the summer surge’s daily-testing peak on July 29. The poll’s next apex came on November 18, when respondents perceived a 26 percent chance of being infected, and the first fall testing peak came on November 25.
The current testing plateau likely reflects what’s clear from the decline in hospitalizations: lower prevalence of the virus. But that doesn’t mean that more testing shouldn’t be done. Landon, for instance, envisions a scenario in which you’d get a rapid test before eating in a restaurant, which would catch at least some cases and help contain the pandemic as certain restrictions lift across the country. “I would have thought, just under a year ago, when we were embarking on testing, we would be in a better place than we are now,” says Melissa Miller, a microbiologist at the University of North Carolina and the chair of the American Society of Microbiology’s clinical and public-health committee. “And we are in a better place than we were a year ago or nine months ago, but we’re still dealing with the same issues that we’ve been talking about for months and months.”
The other problem is that as testing stagnates, it can weaken our best tool for understanding how the virus is circulating. That’s a particular concern with the new, seemingly more infectious variants that are already popping up across the country. If testing drops off too much in response to the current encouraging trends, cases will be missed, putting the country at risk for another surge before vaccines can snuff out the pandemic.