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

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