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## What Testing Capacity Do We Need?

While there is near total agreement that the United States is not carrying out enough SARS-CoV-2 testing to enable it to safely relax social distancing measures, there is no agreed upon benchmark for how much testing we need to do to get there. Rather, several national-level estimates have been put forward based on different assumptions and targets. Here, we briefly review these estimates and compare them to current national and state testing levels. What we find is that while the national estimates vary wildly, the U.S. is still well off the mark no matter which benchmark you use. This is also true for most states, if the benchmark is applied to the state-level.

Existing Benchmarks

We looked at several national estimates, or potential benchmarks, that have been put forward:

1. A group from Harvard has looked at three scenarios for estimating daily testing capacity:
1. Using the standard susceptible-infected-recovered model (SEIR)
2. Using an “equilibrium model”, calibrated to protect hospital capacity
3. Using the experiences of Taiwan and South Korea, two countries that have had success in controlling spread, to calculate a “best case scenario”
2. Scott Gottlieb and colleagues at AEI have talked about a roughly 1% of population estimate to derive the number of tests needed on a weekly basis (though have also suggested 750,000 as a minimum threshold once community transmission has been sufficiently reduced)
3. Paul Romer has estimated that a random selection of 7% of the population should be tested each day.

We summarize these in the table below and also include the share of the U.S. population that would need to be tested under each model (in a given week). As the table indicates, the models vary in their weekly testing target from 3 million to 160 million, accounting for 0.9% of the population for the lowest bound estimate to half of the population in the highest.

 Model Daily Equivalent Weekly Equivalent Weekly Equivalent as Share of U.S. Population Harvard SIER 1-10 million 7-70 million 2.1%-21.3% Harvard Equilibrium 4 million 28 million 8.5% Harvard Taiwan/SK 3 million 21 million 6.4% Gottlieb 430,000 3 million 0.9% Romer 23 million 161 million 50.0%

Another approach could be to estimate the amount of testing needed to identify all infections, based on reported cases. Currently, there are approximately 25,000 newly reported cases per day in the U.S. (the number reported on April 13, for example). We know that is an underestimate – maybe by a factor of 10, as some have suggested – which would mean that there could be 250,000 new infections per day. If we assume that about 20% of people tested are positive (according to the latest data from the COVID Tracking Project), that would mean conducting 1.25 million tests per day or 8.75 million per week, which is about 2.7% of the U.S. population being tested weekly.

(Note that none of these approaches includes any variation by region or state, positivity rate, doubling rate, or other variables, and is applied uniformly to the U.S. Obviously, these factors are quite important.)

Current Testing Levels Compared to Benchmarks

Now, comparing these ranges to current testing shows that the U.S. tested an additional 1 million people in the last week (April 6 to April 13). This is far below all of the estimated targets above and a smaller share of the population (0.3%) than even the lowest target (0.9%). Applying the population share targets to state testing capacity, we find that this is also the case in all states except one – Rhode Island, which tested 1.1%; Louisiana and New York each had tested 0.8% of their populations in the past week, just below the minimum benchmark. Because testing resources have been limited, the focus has been on people who are sick and hospitalized and frontline health care workers, so it is not surprising that Louisiana and New York have higher rates given the scale of infection in those communities.

 Table: Total and Change in Coronavirus Tests from April 6 to April 13, 2020 by State State Number of Tests as of April 6 Number of Tests as of April 13 Change in Number of Tests from April 6-13 Tests in Past Week as Share of State Population US 1,925,000 2,935,000 1,010,000 0.3% Alabama 15,000 29,000 14,000 0.3% Alaska 7,000 8,000 1,000 0.1% Arizona 33,000 43,000 11,000 0.1% Arkansas 13,000 21,000 8,000 0.3% California 117,000 191,000 73,000 0.2% Colorado 26,000 38,000 12,000 0.2% Connecticut 27,000 44,000 18,000 0.5% Delaware 7,000 12,000 5,000 0.5% District of Columbia 7,000 11,000 3,000 0.5% Florida 123,000 196,000 73,000 0.3% Georgia 31,000 57,000 26,000 0.2% Hawaii 14,000 19,000 5,000 0.4% Idaho 11,000 15,000 4,000 0.2% Illinois 63,000 106,000 43,000 0.3% Indiana 26,000 45,000 18,000 0.3% Iowa 12,000 19,000 7,000 0.2% Kansas 9,000 14,000 5,000 0.2% Kentucky 19,000 26,000 7,000 0.2% Louisiana 69,000 108,000 39,000 0.8% Maine 7,000 12,000 6,000 0.4% Maryland 30,000 52,000 22,000 0.4% Massachusetts 76,000 122,000 46,000 0.7% Michigan 62,000 83,000 21,000 0.2% Minnesota 28,000 38,000 10,000 0.2% Mississippi 20,000 31,000 11,000 0.4% Missouri 30,000 45,000 16,000 0.3% Montana 7,000 9,000 2,000 0.2% Nebraska 7,000 11,000 4,000 0.2% Nevada 18,000 25,000 8,000 0.3% New Hampshire 8,000 11,000 3,000 0.2% New Jersey 89,000 129,000 40,000 0.5% New Mexico 19,000 31,000 11,000 0.5% New York 321,000 478,000 158,000 0.8% North Carolina 41,000 63,000 23,000 0.2% North Dakota 7,000 11,000 4,000 0.5% Ohio 48,000 65,000 17,000 0.1% Oklahoma 3,000 23,000 20,000 0.5% Oregon 22,000 31,000 9,000 0.2% Pennsylvania 84,000 130,000 46,000 0.4% Rhode Island 8,000 21,000 12,000 1.1% South Carolina 19,000 31,000 12,000 0.2% South Dakota 6,000 9,000 3,000 0.3% Tennessee 47,000 76,000 29,000 0.4% Texas 85,000 133,000 48,000 0.2% Utah 33,000 46,000 12,000 0.4% Vermont 7,000 10,000 4,000 0.6% Virginia 25,000 41,000 17,000 0.2% Washington 92,000 94,000 2,000 0.0% West Virginia 10,000 17,000 7,000 0.4% Wisconsin 29,000 40,000 11,000 0.2% Wyoming 4,000 6,000 2,000 0.4% SOURCE: KFF analysis of The COVID Tracking Project data reported April 6 – April 13, 2020. Population totals from the 2019 Population data from Annual Population Estimates by State, U.S. Census Bureau.

There is not yet consensus over what approach to testing is required for social distancing measures to be loosened, or exactly how much capacity is needed. But, by any measure, it is clear that we are far from being able to do enough tests to enable us to move to the next phase of responding to the pandemic in states across the country.

Updated on April 27, 2020