In the United States, the number of infected has been doubling every two days. With 20,000 infections and a population of 327 million, it will take 14 doublings before everyone has it:
20,000*2*2*2*2*2*2*2*2*2*2*2*2*2*2 = 327 million.
At the current rate, this will happen in 14 * 2 = 28 days, and occur around April 19.
To prevent this, we need to increase the time to double the infection count. This is why social distancing and shelter-in-place is important. Are they working?
Look for an increase in the days to double and a flattening of the slope of the infection curve. The slope of the United States infection line has held steady or become a bit steeper in the past two weeks. Compare this to the Iran line (which noticeably flattened since the beginning of March).
Put a ruler on an infection curve so it lines up with the past seven days, and extend the line to the right. Do the same for the past fourteen days. This, essentially, is how I made the dashed and dotted lines.
The dashed and dotted lines are an estimate of what the future brings if we continue at the same rate of growth. The difference between the dashed and dotted lines tells how the growth rate is changing.
For example, the Iran dashed line lies below the Iran dotted line. That suggests that Iran is increasing the number of days to double the infection count (from 7.23 days to 9.68 days). In contrast, the United States doubling time decreased (from 2.39 to 2.14) in the same period.
To predict the course of the pandemic, watch the slopes of the dashed and dotted lines. Look for the dashed lines to go below the dotted lines for each region. Look for the curves to flatten. Compare the progress of regions that have already flattened for an idea of what it might look like when your region starts to flatten.
Excellent New York Times Log Plots for Death Rates We can be more certain of death than infection, so curves based on death are more trustworthy. I’m planning to stick with plotting infection rates because this gives an earlier indication of the trends.