Research Question:
Is the covid-19 virus getting worse?
Covid-19 Background
If you have not heard of the covid-19, or corona viurus, by now then you must be Amish or living in your mom’s basement. The most recent stories surrounding the virus has been on the rise in positive test throughout the US. The articles give a sense that the virus is worse than ever before. My first thought after reading the stories was that yes testing has increased, but is this rise in positive tests simply because we are testing more people now. That thought is what inspired me to write this blog. I test numerous measures of how infectious a virus is. The goal of this blog is to answer the question of whether the virus is more infectious now than ever before and what direction the virus is trending. All of the data used for this analysis is obtained from the Our World is Data website.
Positive Tests vs Positive Rate
Most of the news articles reporting on the virus use the daily number of positive tests as a measure of how infectious the virus is. The issue with using the daily number of positive tests is that it could increase due to an increase in testing, not an increase in the spread of the virus. Figure 1 below shows the positive rate and cummulative positive rate of tests to measure how much the virus is spreading. The positive rate of tests is simply the daily number of new positive covid-19 cases divided by the daily number of tests. The cummulative postive rate is the total number of positive tests divided by the total number of tests performed. The cummulative positive rate smooths out a lot of noise in the data.
Figure 1
As you can clearly see the positive rate tests for the virus has declined since the first outbreak and has leveled off in the past month or so. There has been a large increase in the number of tests given. Figure 2 illustrates the growth and Trump’s twitter account will keep you updated on it as well.
Figure 2
Figure 2 leads me to think that the increase in positive cases is due to the increase in testing. Figure 3 visualizes the change in daily positive tests. There is clearly a large jump in positive cases since mide June. Looking back to figure 2, it does not show a sharp jump in the number of tests given. This lead me to question whether the postive rate of tests is a good measure of the spread of the virus.
Figure 3
Number of Tests per Positive Test
The large numbers of tests and positive tests leads to small percent changes in the positive test rate when there is an increase in the number of postive tests. Figure 4 shows a new measure I thought to try, which is the number of tests per positive tests. This measure represents the total number of tests that is given before a positive test is found. The measure is calculated by taking the daily number of positive tests by the daily number of tests performed. The measure moves in the opposite direction of the previous measures. The difference means that the higher the measure is the less the virus is spreading, so the line moving up is good. This measure does a much better job at captureing the recent jump in positive cases since mid-June.
Figure 4
Conclusion
The conclusion of this is that both the total number of positive tests or the positive rate can be misleading when determing how much a virus is spreading. The number of tests per positive test does a much better job at visualizing the change in the spread of a virus. The measure is a little counter-intuitive with a higher number being meaning the virus is spreading less and a lower number meaning the virus is spreading more. Overall I would recommend using number of tests per positive test to measure the spread of the virus versus the other two options.
The spread of the virus is clearly growing since mid-June, so there is some merit behind the articles claiming that the virus is getting worse, but I would not say that the virus is the worse it has ever been. Storylines saying that the highest daily total number of positive tests has been recorded makes a person believe that the virus is worse than it has ever been before. Instead I would say that the virus has clearly taken a turn for the worse and that we are trending towards the virus being worse than it ever has before.