EXPLAINER: Why SC changed the way it calculates percent positive of COVID-19 cases

SOUTH CAROLINA — South Carolina has reported a percent positive rate of COVID-19 cases over 20% for weeks. It was even as high as 31% only five days ago.

But on Tuesday, it was at 8.8%.

The South Carolina Department of Health and Environmental Control is changing the way the rate is calculated. The agency said the change will put the state more in line with other states, and the CDC.

Health officials said the old way was based on people testing positive compared against overall tests.

DHEC decided to use this method early in the pandemic because the focus was on identifying new people who were testing positive. That becomes harder to do when much of the population has been tested.

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The new method compares tests to tests.

Percent positive is now calculated by dividing all positive COVID-19 tests by the total number of COVID-19 tests -- positive and negative -- then multiplying the result by 100 to get a percent.

DHEC said the percent positive number will drop dramatically, but that doesn’t mean the spread of the virus is any less.

“It is important that people understand that while percent positive appears as a smaller number under the new way of calculating the rate, COVID-19 continues to spread at an elevated level in our state,” state epidemiologist Dr. Linda Bell said. “That smaller number is solely based on the change in the way we calculate the rate.”

South Carolina plans to use this method moving forward, and it will go back and recalculate the percent positive for the entire time the virus has been tracked in South Carolina.