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Tracking the Speed of Spread of COVID-19 in West Virginia

I am getting asked more frequently about our approach in tracking the speed of spread of the novel coronavirus in West Virginia. Specifically, does the fewer number of people tested in West Virginia, than some other states, impact our ability to understand where we are with spread of COVID-19?

I believe the answer is we can determine the rate of spread at the rate we are testing.

Here's why.  

Many point out that we need to expand testing in West Virginia, and I agree. While we work with federal agencies and private vendors to have the supplies and reagents needed to increase testing, we can still analyze the data that is coming from those who are tested, to gain insight into the rate of spread of virus to the state. 

As testing increases, we will identify more COVID-19 positive people. The percent of people that are positive will either be proportional (no change in rate of spread) or not proportional (change in rate of spread) to the increased number of people tested.

Note, that by expressing the people with positive tests as a percentage of those tested, we correct for differences in number of people tested.

Then, we can compare West Virginia to other states and countries.  

An important caveat is that we have not changed the criteria for testing. We are only testing people in our state that we consider to either have a high clinical likelihood of being positive, or they are contacts of known COVID-19 positive people, in epidemiological testing.

Thus, we are actually biasing our approach to a higher percentage of COVID-19 positive people than states or countries doing more global testing. 

This way of looking at our testing data allows us to compare our percentage of positive tests to other states. In this comparison, we do well, as the average state rate of COVID-19 positivity is 8-10%. West Virginia is 4%.

However, the greatest utility in these data is to compare the rates on a daily basis. We expect the percentage of positive tests to increase, as the virus is spreading faster in West Virginia.

To date, we are hovering around 4% of tests being positive.

Staying steady for the last four days is good news WV and it suggests that we as a state are making a big difference.

As always, a refresher. If you need to get out, stay away from groups and stay at least 6 feet away from others outside of the people you live with. Wash hands with alcohol content of 70% or higher, or with soap and water vigorously for 20 seconds or more. Get some exercise as a family unit, but stay away from others. Enjoy some sunshine in your back yard.

Great job, West Virginia. Let's keep it up.