Which Covid-19 Numbers Really Matter

This is what to pay attention to, according to an epidemiologist

Anna Maltby
Elemental
Published in
4 min readOct 14, 2020

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Photo: Brian McGowan/Unsplash

For a layperson, national, state, and local Covid-19 data pages seem pretty straightforward (high numbers are bad! low numbers are good!) — until you really start thinking about what this data means for your health and your behaviors. Which numbers are actually important? How do you interpret an increase or decrease in Covid-19 cases or test positivity rates? And how should the data inform what actions you should — or shouldn’t — be taking? To get some clear guidance on how to parse it all, Elemental spoke to Eleanor Murray, ScD, assistant professor of epidemiology and co-director of the Epidemiology Covid-19 Response Corps at the Boston University School of Public Health.

This interview has been edited and condensed for clarity.

Elemental: Where is the best place to find Covid-19 data for your area? And how local should you be going?

Eleanor Murray: For most places, your state health department is a good first stop, but many states are so large that this won’t be specific enough. Local data from your city (or from your metropolitan area in larger cities like New York) will be more useful in those states. Your local health department may have a website that provides these numbers, or your state health department website might provide local numbers as well.

Aside from just generally staying up to date about what’s happening in your area, when is it useful to look at local Covid-19 data?

Local Covid-19 data is most useful when you are making decisions about whether to engage in higher risk activities, such as indoor dining, attending religious services in person, or visiting friends or family in their homes. When Covid-19 rates are low in your area, these may be reasonable to do (potentially with some safety precautions such as masks), whereas during a surge they should be avoided.

What are the most important numbers to look at? What’s the first number you check for your area every day?

I look at a couple of numbers: What are the per capita new case counts and — most importantly — how do they seem to have been changing over the past few days, and what are the test positivity…

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Anna Maltby
Elemental

Editor and writer. Past: Elemental, Real Simple, Refinery29, SELF. Certified personal trainer; prenatal and postnatal exercise specialist. Cat & person mom.