People with multiple negative coronavirus tests are diluting positivity rate in Florida

ORLANDO, Fla. — Some schools are waiting for communities in Central Florida to get down to a 5% positivity rate in COVID-19 cases before opening.

But that's complicated.

Many people who test positive for COVID-19 need multiple negative tests before returning to work.

Read: 229 more deaths in Florida linked to coronavirus, 6K new cases

The state is counting every time someone tests negative, which is diluting the positivity rate.

Adding the new number of positive and negative cases each day will calculate the total number of tests.

Then we divide the positive cases by the total to get the positivity rate.

For Friday, 6,148 divided by 39,467, will gave a sate of 0.1557. And then you move the decimal over two places, the positivity rate is 15.6%

((THREAD)) Most of you know, I calculate the statewide positivity rate on my own each day. (15.6% today) I do this because the state positivity rate (seen below) counts every negative test, which dilutes the rate. Especially when the NBA is testing hundreds a day. (1/3) pic.twitter.com/z1M3k1VT9z
— Lauren Seabrook (@LSeabrookWFTV) August 14, 2020

These numbers all come directly from the Florida Department of Health's daily COVID-19 report.

But if you scroll to the bottom of the second page, where the state discusses positivity rate, you see a different number, 8.08%.

"It's nothing wrong. It's how you decide to do it," Orange County health officer Dr. Raul Pino said.

The state is not counting double positives into its numbers, but it is counting double negatives.

For example, a woman said she has been tested seven times. She tested positive three times and negative four times.

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Which means she counted in the system as one positive case and four negatives. And when you count multiple negatives, it dilutes the positivity rate.

That is why the state said the positivity rate is about 8%, but the numbers added up to more than 15%.

“It’s super safe to assume that the positivity rate in our community is higher than what we have,” Pino said.

As the pandemic evolved, public health researchers realized there were new ways to collect and present the information, he explained.

“We didn’t envision probably that people would be testing multiple days,” Pino said. “We didn’t envision at the beginning that the NBA would be here, and we’d be testing everyone every day.”