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COVID-19 data: What the numbers mean and how to tell if the coronavirus is spreading

Ryan Blethen, The Seattle Times on

Published in Health & Fitness

In mid-June, the agency revealed it had been reporting incorrect COVID-19 testing numbers for eight weeks by overcounting the number of people who tested negative. The state COVID-19 dashboard was mistakenly including negative antibody tests with negative molecular tests, showing 13% more people testing negative than actually had. This miscalculation made it appear as though a smaller proportion of the state's population was infected.

How many tests vs. how many positive

The positive test rate or% positive shows how many of all tests administered have come back positive for infection. Watching changes to this number can help us understand whether the virus is spreading more rapidly.

But there are caveats. An extremely high positivity rate could indicate that a county, state or nation is only testing the sickest people, or those who are receiving medical attention. The more people get tested, the more accurate the positivity rate is for a population.

Look at bed capacity

The number of COVID-19 patients sick enough to require hospitalization has been a key indicator for understanding the severity of this disease and the pandemic's impacts on the health care system.

 

Lots of people may contract the illness, resulting in soaring daily case counts. But for hospitals managing finite resources of staff, beds and equipment such as ventilators, the big concern is the number of people who require their care.

The state Department of Health and the Washington State Hospital Association track the number of hospitalizations here. But overall statewide numbers don't tell the whole story. As case counts and hospitalizations soar in one area, patients might be transported from an overburdened hospital to one that has more resources.

Spreading the virus

The basic reproduction number, expressed as R0 ("R-naught"), shows how much an infected person is spreading the virus. If each infected person gives the virus to more than one other person, that can indicate that an outbreak is getting worse.

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