Caselaw Visualizations

Epidemiology Through Caselaw – Learning From Yellow Fever

The COVID-19 global pandemic has already left its legal footprint quickly making its way to the United States Supreme Court. Law firms, too, are wasting no time in preparing for the onslaught of client questions and legal cases related to the pandemic that is sure to come.

The profound impact of the measures being taken to contain the spread of the novel coronavirus (“COVID-19”) is creating a host of … legal concerns relate[d] to corporate governance, disclosure, contracts, financing, strategic transactions, employment and others.

White & Case; see also Sidley

Christopher Tung, of K&L Gates LLP, has even released a helpful flow chart mapping how COVID-19 may or may not trigger Force Majeure clauses in contracts (for businesses operating in Mainland China and Hong Kong).

The Legal Consequences of COVID-19 on Your Contracts: Force Majeure in Different Jurisdictions and Industries, and Some Practical Guidance

Not only has such disruption led to the legal questions above, it has already led to over 1,000 cases that contain the term “COVID-19” (as of April 20, 2020 on WestLaw; cases refers to legal cases not epidemiological cases). This is not the first time, however, that epidemics and pandemics have left lasting legal footprints. In this post and over the next few weeks, I plan to release a number of visualizations raising thought-provoking questions and potential lessons to learn from the impact of historical pandemics have had on the American caselaw.

Let’s begin with Yellow Fever as it offers a clear picture into how caselaw can be used to visualize the timeline, geography, and magnitude of disease-related disruptions to our daily lives.


Instructions: Explore the interactive data visualizations on this site by clicking on the data points you wish to learn more about. On wider screens, depending on the type of visualization, you may see the option to display only the states you wish to learn more about on certain types of charts.

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Nowadays, “Yellow Fever can be prevented through vaccination and mosquito control” and the “vaccine is safe and affordable, and a single dose provides life-long immunity against the disease.” But that was not always the case; in 1699, Thomas Story journaled:

In this distemper had died 6, 7, and sometimes 8 in a day, for several weeks, there being few houses, if any, free of the sickness. Great was the fear that fell on all flesh! [He] saw no lofty or airy countenances nor heard any vain jesting to move men to laughter…But every face gathered paleness, and many hearts were humbled, and countenances fallen and sunk, as such that waited every moment to be summoned to the bar and numbered to the grave.

Thomas Story, A Quaker Diarist, Quoted in John Duffy, Epidemics in Colonial America, Baton Rouge: Louisiana State University Press, 1953.

The last yellow fever epidemic on the North American continent occurred in New Orleans, Louisiana” in 1905. The geographic concentration of this disease in the American South can be seen in the following map of US cases:

The first case of yellow fever to strike Louisiana occurred in 1769, but the first epidemic transpired in 1796 when 638 people (out of a population of 8,756) died from the disease, translating into a mortality rate of 72.86 per thousand. In the 100-year period between 1800 and 1900, yellow fever assaulted New Orleans for sixty-seven summers. Its main victims were immigrants and newcomers to the city, and for this reason it was also referred to as the “stranger’s disease.” The worst epidemic years coincided with some of the highest levels of Irish and German immigration into the city: 1847, 1853, 1854, 1855, and 1858.

Laura D. Kelley, 64 Parishes

Regarding the city’s valiant response in the 1905 epidemic, Rupert Boyce noted:

In one respect New Orleans has set an example for all the world in the fight against yellow fever. The first impression was the complete organization of the citizens and the rational and reasonable way in which the fight has been conducted by them. With a tangible enemy in view, the army of defense could begin to fight rationally and scientifically. The… spirit in which the citizens of New Orleans sallied forth to win this fight strikes one who has been witness to the profound gloom, distress, and woe that cloud every other epidemic city.

Rupert Boyce, Dean of Liverpool School of Tropical Diseases, 1905

But is was not just New Orleans that faced the heavy realities of Yellow Fever in the 20th century. Tennessee, Mississippi, Louisiana, and to some extent Kentucky all have disproportionately more cases about Yellow Fever than the rest of the United States.

Interestingly, it is possible to see in the caselaw the invention of Yellow Fever Vaccine in 1938. After 1938, the peak of cases about Yellow Fever crashed:


Word frequency for each state is determined by dividing the number of times “yellow fever” appears over the total number of words each state’s corpus (the total combined body of caselaw).

Word Frequency =(Word Count of "Yellow Fever")/(Total Word Count)

Case frequency for each state is determined by dividing the number of cases that contain “yellow fever” over the total number of cases in each state.

Case Frequency =(Cases that Contain "Yellow Fever")/(Total Number of Cases)


Do you have any guesses or explanations about the findings shown above? Do you have any additional visualizations concerning epidemiology and law? Let me know @JoaoMarinotti on Twitter. This post is part of the Caselaw Visualizer Project. For a description of the dataset and the processes used to generate these visualizations, click here. The data was made available by the Harvard Law School Library’s Case Access Project (found at Case.Law). For information about me, click here.

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