What has happened?
The cases and deaths can be deceiving for several reasons:
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The detected cases depend on the testing capacity of the country or region. A country unable to test will detect fewer cases and appear less serious. That’s why it’s important to track the number of tests performed and the percentage of positive tests, as well as the number and percentage of deaths.
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The detected cases reflect measures taken 2-3 weeks ago, considering that when there is a contagion, it takes an average of 5 days to show symptoms, which gives way to the person being tested, and from the time the test is performed until the results are publicly reported, the average time to publicly report the results is between 10 and 15 days, depending on the city. In other words, the fact that detected cases are on the rise does not mean that the overall situation has not improved in the last two weeks (see next section for better understanding).
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The deaths reflect measures and behaviors taken about a month ago, considering that the average between infection and death is 19 days, and there is an additional delay in reporting deaths of between 7 and 14 days, depending on the country and region. The fact that deaths are on the rise does not mean that the overall situation is not under control.
What can we expect in the coming days?
The trend in the daily percentage increase is important because it allows to immediately understand if the measures taken have worked and the situation is being controlled:
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When the cases are increasing, and the daily percentage increase is also growing, the situation is out of control; however, if the cases are increasing but the daily percentage increase is decreasing, it indicates that in a couple of weeks the curve should reach its peak and begin to decrease.
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When the curve begins to drop, the percentage increase must be negative for several days in order to make the measures more flexible and reopen the city.
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A negative percentage increase indicates that, on average, each person with the virus infects less than 1 person (metric known as R = reproductive rate), so the curve will continue to fall.
How well is the quarantine being enforced?
With the movement of cell phones, Apple and Google calculate how much the population of a region has stopped moving, compared to the usual behavior (before March, which is considered the base, or 0%). The regions that best comply with the quarantine reduce mobility by at least 50%, with some even approaching 80% on the most critical days.
