COVID-19: What is an incidence rate?

Mary Beth Sallee

Reporter, Hart County News-Herald

 

As the COVID-19 pandemic continues on, much discussion has revolved around what an incidence rate is and how it affects local decisions.

According to information received from the Barren River District Health Department (BRDHD), an incidence rate is used to gain a better understanding of the spread of COVID-19 within counties and communities.

An incidence rate is calculated by comparing the number of positive tests in a county by the total population of that county and then multiplying it by 100,000 to have incidence rates in the same format for each county across Kentucky.

In using Barren and Hart Counties as an example, if Barren County has 423 total positive COVID-19 tests within one week (7 days), then 423 is divided by 7. Therefore, 423 divided by 7 equals an average of 60 new positive tests a day. Those 60 new tests are then divided by Barren County’s 2019 population estimate of 44,249 people. That total is then multiplied by 100,000. Therefore, based on the numbers stated above, Barren County’s incidence rate would be 135.6 per 100,000 people.

If Hart County, for example, has a total of 133 positive tests within one week (7 days), then 133 is divided by 7 for a total of 19. Those 19 new tests are then divided by Hart County’s 2019 population estimate of 19,035 people. That total is then multiplied by 100,000. Based on the numbers stated above, Hart County’s incidence rate would be 99.8 per 100,000 people.

The State, as well as the Center for Disease Control and Prevention (CDC), not only use the incidence rate to compare how fast COVID-19 is spreading in a population or county, but also to determine the severity of COVID-19. Counties are designated into severity zones such as green (low severity), orange (accelerated or medium severity) and red (critical or high severity). These “zones” have often been used to determine local decisions such as what events should or should not be held or if masks should be required for students in school.

As of October 1, every county in the BRDHD area – Barren, Butler, Edmonson, Hart, Logan, Metcalfe, Simpson, and Warren Counties – were all designated red zone counties based on incidence rates.

It should be noted that an incidence rate does not show how sick infected individuals are. BRDHD states that the best ways to help lower incidence rates include wearing a mask, washing hands, social distancing, and getting vaccinated.

For additional local information regarding COVID-19, visit the BRDHD website at www.barrenriverhealth.org or follow BRDHD on Facebook, Twitter, and Instagram. The BRDHD district office can also be reached by calling 270-781-8039.