I used to speak at conferences far more than I do now. Between speaking engagements, work travel and vacations I was probably on a plane more than a dozen times a year. Over the years I noticed that I was far more likely to come down with a cold or the flu a few days after a flight than times when I had not traveled. One time I spoke on Obamacare for the Denver Federalist Society with plans to stay over and ski Arapahoe Basin. Two days later I had a severe cold. I could have been the unwitting vector who helped spread a virus from far flung places to Dallas.
I never complained about mask mandates on airplanes. Being couped up in an aluminum tube with 200 other people made me happy to wear a mask. Air travel allows contagious diseases to spread like wildfire. What was confined to China or Europe last week can easily take hold in Kansas by next week.
I learned in history class that hundreds of years before covid, ships spread diseases from one region to the next. Diseases supposedly leaped from the Old World to the New World with devastating results, and New World Diseases made their way back to the Old World. Supposedly, Alexander the Great brought back dysentery from India to Europe with his soldiers. Europeans spread Smallpox to the Americans, making conquest possible. Syphilis may have come from the New World to plague the Old. While we’re talking about plague, the Bubonic Plague spread from seaports inland. This from The New York Times:
[S]hips could be hotbeds of disease, Ms. Blackmore said. Contemporaneous reports of conditions on ships in past centuries were horrific — they were suffocatingly crowded and lacked sanitation.
Yet, a new study claims ships were not what often what spread viruses, however. Mathematical modeling suggests it was rare.
A new report, published last week in The Proceedings of the National Academy of Sciences, uses mathematical models to show how viruses had to beat very long odds to be transmitted across the sea. Most often, the study found, infectious diseases burned themselves out on board before ships ever docked.
When did travel become so swift that diseases easily spread by travelers? That was the mystery researchers set out to discover.
Elizabeth Blackmore, a doctoral student at Yale, and James O. Lloyd-Smith, an ecologist at the University of California, Los Angeles, set out to find the moment when viral transmission started to change.They learned that the first reports of smallpox outbreaks of smallpox in California were not until 1806 and 1838. And smallpox was first reported much later elsewhere in the Pacific.
What accounts for the late response to smallpox in the Pacific when it is thought to have infected the New World 300 years earlier?
She noted that the only way a disease could be transmitted after a ship docked was if there was a chain of infections on board that lasted at least as long as the ship’s journey. Often in the days of sailing ships and even with many steamboats, that simply could not happen. The usual situation was that by the time a ship reached its destination, everyone susceptible to a disease on board had been infected and had either recovered or died.
The researchers modeled influenza, measles and smallpox. Flu is infectious for only three days, while measles is infectious for nine and smallpox for 20.
They calculated that if one person had the flu while sailing on the Santa Maria in 1492, there would have been a less than 0.1 percent chance that the disease would be transmitted to the New World. If one person had measles, the chance would have been 24 percent. For smallpox, 33 percent. The Santa Maria trip, with 41 people on board, took 35 days, so the limited number on board and the length of the trip contributed to the small chance of disease spread.
What changed? When steam power replaced sails, ships became faster, reducing the time it took to reach their destination. In addition, steamships were larger with more people aboard. For an infectious disease to reach a destination, the length of the trip either had to be short, or the number of potential victims large enough to keep the virus alive until the ship docked.