There's no doubt that a lot of our current attention goes to the COVID-19 infection cases, as media outlets publish updated numbers on-air or online every day. Time is a critical factor for us to grasp what's happening during the outbreak, but it also obscures some of the most vital information.
For instance, the spread of the novel coronavirus started at a different time in different countries. And the countries where the infection arrived later (say Italy and other parts of Europe) than others, witnessed a much faster spread. Therefore, if one wishes to compare the growth rate across multiple countries, plotting the new cases or cumulative cases against time won't provide much of an answer.
So how do we know if a certain part of the world is heading toward recovery? How do public health experts obtain definitive evidence that the quarantine in a region is working or not?
In a collaborative data visualization project, MinutePhysics Youtube channel showcased a graphic way to see the COVID-19 pandemic without taking consideration of time.
Other than plotting x- and y-axis linearly, their trajectory graph uses a logarithmic plot, meaning each tick on the axis represents a tenfold increase over the previous one. But the critical take-away point is that time is irrelevant when interrogating the exponential growth of infection. The chart plots the growth rate against the cumulative cases, showing a "straight" line of growth where data from all countries line up with, no matter how many cases they have and when their patient zero appears. More importantly, those in recovery, or have their domestic curve flattened, shows a vertical drop below the growth line.
Source: MinutePhysics via Youtube