Covid Tests Conducted Per Confirmed Case

While the covid death rate has been declining in the US, the rate of newly diagnosed cases has remained plateaued. The rate of testing has increased, while the test-positive rate has decreased: does that mean that the case-rate plateau is merely a methodological artifact, and that new cases are on the decline?

As discussed in prior posts, the rate of new diagnoses underestimates, perhaps as much as ninefold, the number of new infections, so trends in this indicator aren’t very informative. At the state-by-state level, testing rate remains positively correlated with test-positive rate and death rate. These statistical interrelationships suggest strongly that testing in this country remains tied to clinical treatment of active cases, rather than having shifted to the population screening and contact tracing required for keeping the viral reproduction rate low and eventually extinguishing the epidemic.

Divide total tests by test-positives to get the ratio of tests conducted per confirmed case. The lower the ratio, the more active the contagion in the community; the higher the ratio, the more proactive the public health preventive measures. How does the US ratio compare with other countries on tests per confirmed case? Here are some results derived from an interactive map:

  • Mexico:   2
  • Argentina:   4
  • Sweden:   9
  • India:   13
  • US:   14
  • Russia:   35
  • Netherlands:   42
  • UK:   51
  • Czech:   58
  • Japan:   62
  • Canada:   93
  • Spain:   117
  • Germany:   132
  • Ireland:   165
  • Italy:   187
  • Switzerland:   240
  • Denmark:   329
  • Norway:  368
  • Australia:   3,244

While not a perfect correlation, countries with a higher ratio of tests per confirmed case also have more rapidly decreasing covid death rates — a strong indicator of successful control over the epidemic. The US has a long way to go.

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