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Mapping the Virus

The study of Geography and the use of its most prominent tool – mapping — has been invaluable in the research into epidemics. Dr. John Snow’s map of the 1854 cholera outbreak in London is widely credited with making the first inroads for germ theory. (

In the current corona virus pandemic, there are data available to the public about testing, infections, and deaths. While the Centers for Disease Control (CDC) has data about positive tests at the state level (, other credible sources such as the New York Times have county-level data that include numbers of deaths ( The COVID Tracking Project ( has data on total tests administered as well as the number of positive tests.

I have used these data along with information from the US Census Bureau ( to map various aspects of the corona virus. I have used Microsoft Excel to process the data and a simple on-line mapping program ( to visualize it.

I will make an effort to post a new or different map every few days.  Data change daily. Because of this, categories will most likely change as well and so comparison to past maps may not be fruitful.

Map of poeple testing positive for corona virus in Wisconsin counties as a percentage of population


  1. slbenson slbenson March 29, 2020

    Seems the infected counties are mostly along the major highways and interstates!

    • Anita Peterson Anita Peterson Post author | March 30, 2020

      Good eye. That’s certainly the case. Of course, it’s a chicken-and-egg issue: Our most populated places are along the major roads and the major roads were put in to connect the populated places. But, yes, as this is a map that is corrected for population (being a percent positive of total county population) there is certainly something to it – people spread it to people and transmission is greater in more densely populated areas.

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