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int comp stats
This figure shows the 7-day moving average of each country’s daily positivity and daily tests conducted per capita.
The U.S. has conducted more COVID-19 tests than any other country. However, there is no expert consensus on a recommended target for the raw number of tests or even the rate of tests per capita.
In order for governments to identify new cases and effectively respond to the pandemic through tracing and treatment, testing programs should be scaled to the size of their epidemic, not the size of the population. In this visualization, you’ll see that several countries effectively controlled the spread of the virus through testing programs that had a far lower number of tests per capita than the U.S. Meanwhile, despite having the highest rate of tests per capita, the U.S. faces the largest outbreak in the world and new cases continue to trend upwards in many states.
Another way of looking at the extent of testing relative to the scale of the outbreak is to ask: How many tests does a country do to find one COVID-19 case?
Countries that do very few tests per confirmed case are unlikely to be testing widely enough to find all cases. The WHO has suggested around 10 – 30 tests per confirmed case as a general benchmark of adequate testing.
Test per confimed case
This chart shows the number of daily tests per thousand people. Because the number of tests is often volatile from day to day, I show the figures as a seven-day rolling average.
What is counted as a test?
The number of tests does not refer to the same in each country – one difference is that some countries report the number of people tested, while others report the number of tests (which can be higher if the same person is tested more than once). And other countries report their testing data in a way that leaves it unclear what the test count refers to exactly. I indicate the differences in the chart
per 1000 ppl
Here I show the share of tests returning a positive result – known as the positive rate.
This metric offers us two key insights: firstly as a measure of how adequately countries are testing; and secondly to help us understand the spread of the virus, in conjunction with data on confirmed cases.
The positive rate is a good metric for how adequately countries are testing because it indicates the level of testing relative to the size of the outbreak. To be able to properly monitor and control the spread of the virus, countries with more widespread outbreaks need to do more testing.
share of positive covid
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