South Florida

Prevalence of Virus Leveling Off in State, South Florida

Rather than react to one-day changes in positivity rates, experts advise longer time frames are more meaningful.

NBCUniversal Media, LLC

Each day, the Florida Department of Health releases hundreds of pages of data on coronavirus cases across the state.

One of the most-closely watched metrics is the percentage of tests that come back positive.

Because that can be a fickle figure -- fluctuating day to day for various reasons -- epidemiologists say it's more valuable when examined over longer time periods.

NBC 6 has been keeping seven-day weighted averages for the state and Miami-Dade and Broward counties.

Those trends show the prevalence of the virus has largely levelled off in recent weeks, though Miami-Dade has seen a very slight uptick of late.

Statewide, for the week ending Sept. 1, the positivity rate for all tests was 7.8% (the state also tracks positivity for new cases, but these numbers are for all test results received). Over the next seven days, the rate dropped to 7.4%, then down to 6%, 6.1%, 5.8% and, finally, 5.6% for the week ending Tuesday.

In Miami-Dade, the positivity rate for new cases fell from 7% for the week ending Sept. 1, to 6%, 4.7% and 4.2% in subsequent weeks. But it then increased to 4.9% for the weeks ending Sept. 29 and Tuesday.

Broward has done better. Its new case rate dropped from 4.6% for the week ending Sept. 1, to 3.8% the following week and has hovered around 3% for the seven days ending on Tuesdays ever since: 2.9%, 3.1%, 2.9% and 3.1%.

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