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As Coronavirus Surges, How Much Testing Does Your State Need To Subdue The Virus?

A sign alerts residents to a mobile COVID-19 testing site in Chicago, Illinois. Policy makers continue to urge greatly expanding coronavirus testing as a means of detecting and containing emerging outbreaks.
Scott Olson
Getty Images
A sign alerts residents to a mobile COVID-19 testing site in Chicago, Illinois. Policy makers continue to urge greatly expanding coronavirus testing as a means of detecting and containing emerging outbreaks.

The coronavirus keeps spreading around the United States. New hot spots are emerging and heating up by the day. The death toll keeps mounting. So how can the U.S. beat back the relentless onslaught of this deadly virus?

Public health experts agree on one powerful weapon that's gotten a lot of attention but apparently still needs a lot more: testing.

A new analysis that researchers at Harvard conducted for NPR finds that more states have begun to do enough testing to keep their outbreaks from getting worse, but most are still falling short.

And perhaps more importantly, a consortium of public health researchers, including Harvard, finds that only a handful are doing enough testing to effectively suppress the virus, that is, to bring new cases down to a low enough level to allow everyday life to return to some semblance of normalcy.

"That's what we all want — to get our lives back. But right now we're losing to the virus," saysAshish Jha, who runs the Harvard Global Health Institute.

When NPR and Harvard firstanalyzed testing on a state-by-state basis May 7, the nation was conducting about 250,000 tests every day, and according to the analysis, only nine states were doing enough testing to keep their outbreaks under control.


Now, daily testing has doubled to about 500,000 nationally, and 18 states plus Washington, D.C., are currently testing enough to keep their outbreaks from getting out of control. But the national totals are far below what the Harvard group says is needed to contain the current outbreaks — 1 million tests daily — and yet farther from a level that could truly beat back the pandemic in this country.

"I see that as progress that we now have more states that are able to manage and mitigate the virus," Jha says. But he adds, "what we all really want is to suppress the virus — to get the virus level so low that we don't have large numbers of people getting sick and dying and that we can open up our economy."

Moving from mitigation to suppression

In the analysis presented here, states' current testing levels are compared to two testing targets. The less ambitious target is intended to achieve what public health experts call "mitigation." This means keeping the size of current outbreaks from growing; this approach requires enough testing to get to 10% or fewer positive tests.

Thirty-two states currently aren't doing enough testing to achieve mitigation. That's probably one significant reason why alarming spikes in infections are erupting in hot spot states across the South and West.

"The surges we're seeing in large parts of the country are due in part because those states opened up too quickly and they relaxed way too much given how much virus they had in their community — and they lacked testing," Jha says. "These two things really go hand in hand."


The second, more ambitious set of targets is intended to achieve suppression, a strategy many public health leaders are now calling for. Suppression means greatly reducing new infections and keeping them low enough to safely open public life again.

Both of these strategies require communities to have other crucial measures in place. For testing to be effective, communities must have enough health workers to trace contacts,following up with people who test positive and their contacts and helping them quarantine so they don't spread the infection. Widespread mask use, social distancing and hand-washing also are important.

The main difference between the two strategies is that suppression calls for much more aggressive and consistent testing of high-risk individuals to allow communities to clamp down on emerging case clusters faster.

To achieve suppression, states and institutions need to take a proactive approach to testing and "cast a much wider net," Jha says.

How to achieve suppression

So how much testing would be needed to go beyond mitigation and actually achieve suppression?

For that, the Harvard Global Health group developed a new metric in collaboration with other academic groups across the country: They estimate that communities need to test widely enough so that the number of people testing positive for the virus is 3% or lower. That's the positivity rate that other countries, such as Italy and South Korea, achieved to control their epidemics.

According to the new analysis, the U.S. overall would need 4.3 million tests per day, with the amount of testing in each state varying depending on the current size of their outbreaks, to achieve that goal. (This analysis assumes the true size of each state's outbreak to be three to five times larger than what's captured in confirmed case numbers.)

It's worth noting that these figures are based on projections of each state's expected outbreak size by July 6. These testing estimates reflect a snapshot in time and could shrink or grow depending on how facts on the ground change.

The goal of this more ambitious level of testing is to free states up from the constant fear of hidden outbreaks bubbling up. It could bring communities to the point "where people will have confidence going out to restaurants and bars and opening up schools without having large outbreaks and without having to shut down again," Jha says.


Increasing testing is not simply a matter of ensuring an adequate supply of tests to existing testing sites. Jha's group recommends that communities test much more strategically.

For example, frequent, regular testing could be targeted at people in high-risk settings such as nursing homes, meat-packing factories and prisons. Universities, when they reopen, could test students weekly; schools could test teachers regularly, and hospitals could provide testing not only to employees, but to their families. This approach would also spot many more asymptomatic or presymptomatic cases, people who are infected and could still be spreading the virus even though they haven't developed symptoms.

Challenges ahead

According to the new analysis, only four states are doing enough testing for suppression: Alaska, Hawaii, Montana and Vermont — all relatively small populations with small outbreaks. West Virginia is close to its target.

Among states with large outbreaks, New Jersey is close to being in a position to suppress the virus, showing that even a larger outbreak can be brought under control.

"I do think it's possible. It's not going to be easy. But it requires leadership and it requires a commitment from our country that says, 'We actually want to open up our country safely and we want to get our lives back,'" Jha says.

Others agree that the need to ramp up testing is urgently needed, but argue that it remains a daunting goal.

"It's disappointing and it's frustrating that we don't have the capacity to get this under control," says Dr.Marcus Plescia, chief medical director for the Association of State and Territorial Health Officials. "This is particularly concerning now that we're seeing surges in cases. We clearly need to be able test more people."

Plescia says the main bottleneck to getting enough testing continues to be chronic shortages of the test kits themselves as well as the supplies needed to perform the tests.

"This is the real challenge across the world," Plescia says. "Everyone is competing for these tests."

Jennifer Nuzzo, an epidemiologist at Johns Hopkins tracking testing who is not involved in the Harvard analysis, questions the usefulness of projecting specific numbers of tests needed to control the virus. Instead, Nuzzo says her group has long advocated focusing on the percentage of people testing positive as a more reliable metric. The lower the percentage, the greater the chance testing is catching enough new infections to control the virus, Nuzzo says.

"There are some visions that we're going to be testing everyone. I don't envision that we are ever going to be testing so broadly," she says. "I'm much more interested in figuring out who is likely to be infected and bring the tests to them rather than testing an entire state."

Jha recognizes these are ambitious — some would say unattainable — targets. But, he says, the key is to start moving in the right direction, to make progress in expanding testing, in order to "avoid a roller-coaster of openings and closings."

"If we don't start working toward this goal now, it will be a very difficult fall and winter," he says.

Copyright 2023 NPR. To see more, visit https://www.npr.org.


Rob Stein is a correspondent and senior editor on NPR's science desk.