Metrics for COVID-19 Spread

For Greenville County Schools

Emily Gill
June 26, 2020 - 1:21 pm
Students with Masks - Getty Images

Released by Greenville County Schools.

On Thursday, DHEC released to superintendents the system it has established for determining Low, Medium and High spread of COVID-19 and a current rating for each county using three data points: Two-week cumulative incidence rate, Trend in incidence rate, and Two-week percent positive rate.

Low, Medium and High spread ratings match language in the AccelerateED task force’s recommendations for determining the appropriateness of in-person activities at schools. 

“We are most appreciative to now have direction and definition for the degrees of impact established by the medical and public health experts at DHEC,” said W. Burke Royster, Superintendent of Greenville County Schools. “These levels of impact will help guide us in applying recommendations made by the AccelerateED Task Force.

Using a two-week look back at data, DHEC will average the three categories to establish the overall rating for each county.

In the examples given in its memo, ratings of two mediums and one high equate to a medium rating, two highs and one medium result in a high rating, and one low, one medium, and one high equates to a medium rating.

The DHEC memo is available here.

Included below is a breakdown of the metrics and categories, as well as a brief descriptor of the action that should be taken, following the AccelerateED Task Force Recommendations. Greenville County is currently rated as High in all three categories, resulting in an overall rating of High.

Metrics and Categorizations

Two-week cumulative incidence rate: The number of new cases in the prior two weeks per 100,000 people. This metric provides the recent incidence of COVID-19 infections in that county. Categorization (# cases/100,000 people):
o Low: 0 – 50

o Medium: 51 – 200

o High: ≥ 201

Trend in incidence rate: Whether the two-week incidence rate is increasing, decreasing, or stable compared to the previous two weeks. For purposes of this assessment, consider the trends to be equivalent to:
o Decreasing = Low

o Stable = Medium

o Increasing = High

Two-week percent positive rate: the percentage of individuals who tested positive out of the number of individuals tested with a molecular (swab, or PCR) test in the last two weeks for each county. The metric takes into consideration the number of tests performed in the county in the prior two weeks. Categorization:
o Low: ≤ 5.0%

o Medium: 5.1 – 9.9%

o High: ≥ 10.0%

Recommended Action for School Districts Based on Overall Spread Rating

Low: Modified Traditional Scheduling – Students and staff may return to school buildings with modifications to their scheduling and instructional practices to mitigate continued risks related to COVID-19.
Medium: Hybrid Scheduling – Only a portion of staff and students can report to a physical school building due to a combination of health requirements and facility/space limitations.
High: Full Distance Learning – No students and only essential staff report to school locations.


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