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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

How to compare areas

Places with bigger populations are likely to have more cases, simply because more people live there. So to compare one place to another, get the rate by looking at the number of cases per 100,000 residents rather than looking only at totals.

This number is important because it's one of the ways Washington state determines whether counties are ready to move forward in Gov. Jay Inslee's four-phase Safe Start reopening plan. When Secretary of Health John Wiesman decides whether a county can move to the next phase, he generally wants the county to have had 25 or fewer new infections per 100,000 residents over the past two weeks. (The magic number was originally 10 cases per 100,000, as recommended by the U.S. Centers for Disease Control and Prevention, but was later relaxed to 25.)

2 kinds of tests

There are two types of tests involving COVID-19: molecular (viral) tests and antibody (serology) tests.

A molecular test is used to diagnose whether a person has an active infection. It's typically administered with a long swab, which takes a sample that is then processed at a lab. The results are reported to local and state health departments.

 

An antibody test, which is done with a blood sample, detects whether someone has been infected in the past and developed antibodies to the virus.

While antibodies might provide some immunity, it isn't yet known how long COVID-19 antibodies last in the body or how effective they are at preventing another infection from this coronavirus.

Washington state's Department of Health has struggled to share accurate test information with the public.

At the end of March, DOH's disease reporting system was flooded with case data, which temporarily stopped the state from publicly reporting the number of new COVID-19 cases.

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