Droplets from coughs or sneezes from an infected person can be left on surfaces and then touched by uninfected people. If those people do not wash their hands thoroughly before touching their eyes, nose or mouth, they can become infected with a virus and then go on to infect others.

Respiratory viruses include influenza as well as those that can cause influenza-like illnesses, such as upper respiratory infections (the common cold), viral sinusitis, viral bronchitis and viral ear infections. Every year, they infect millions and kill thousands of Americans; health officials closely track cases by the week.

How we conducted the experiment

To test the hypothesis that these elections could lead to more viral infections, we used a large national insurance database focusing on the years 2007 to 2016. This database included more than 14.5 million patients over 40, an age group we chose to study because they are more likely to vote.

We calculated rates of influenza infection or influenza-like illness for the 21 days after federal elections, which fall on the first Tuesday of November. We chose a 21-day window to allow enough time for any newly infected patients to fall ill and seek medical care. In years without an election, we calculated infection rates for the 21 days after the first Tuesday of November — the day that would have been Election Day had there been a federal election.

We then grouped the data into years with a presidential election, years with a midterm election, and years with no election. Although state or local elections might have taken place in the years without a federal election, they would have drawn far fewer voters, and so these years made a good group for comparison.