Local engineer explains the curve

Engineer Lynn Sebourn, who serves as Coffee County commissioner, explained the curve and how it could potentially change. He urged locals to take the situation seriously. 

"We are now up to 1,203 confirmed cases and six deaths," Sebourn said March 27. "Today's plot is a little different. The left hand axis is a logarithmic axis. This means that every line across the screen is 10 times greater than the previous line. This kinda 'squishes' the numbers together as you move up. Why plot it like this?"

These plots are useful for looking at exponential growth, said Sebourn. 

"On a log chart an exponential growth plots as a straight line," he said. "So you can see from the plot how long many days it takes to get 10 times larger. From the plot it took about eight days to get from 10 to 100. If the growth continued at the same rate in another eight days it would increase from 100 to 1000. I also plotted an orange line showing a forecast.

"The forecast line is based on the average growth over the past five days. Right now the daily growth over the last 5 days has averaged about 20%. Based on this we will get to 10,000 cases in about 12 days. If the growth continues like this we would reach 100,000 cases only 12 days later."

This growth rate is why health officials are so concerned.

"There are several things that could affect this line," he said. "First of all, there is a lot additional testing coming on line. Once we start to test a lot of people, the numbers will jump up more. But this is not bad news by itself. These people are already infected, we just don't know it yet. If our social distancing works, the increase in the line should come down. If you look at the chart, the line flattens some around March 23. Maybe our efforts are working. I hope so. Eventually if the epidemic continues, the spread will decrease naturally because enough people will have already had the virus that it can't pass from one person to another as easily."

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