 reason Wuerth believes the two plagues are different is because there is an immunity to the medieval plague and there isn’t to the modern plague. In the multiple outbreaks that occurred in the medieval plague, Wuerth said child mortality decrease with each outbreak in Sienna and Pisa, suggesting immunity to the Black Death.
Matteo Villani was a Florence chronicler at the time of the Black Death. He said the disease “struck most vigorously those areas such as Brabant and Bohemia that had not been affected the first time around.” This observation suggests there was perhaps an immunity to the medieval plague, unlike the modern plague, which humans have no immunity to.
The fifth and final point Wuerth made as to why the medieval plague might not be the modern plague is that the seasonality of the two are quite different.
The medieval plague struck the worst during the dry and hot months of July and June. Giovanni Morelli, a Florentine doctor during the medieval plague, said, “Deaths from the plague will mount in June and peak by the middle of July.”
The peak months of dryness, June and July, also coincided with the peak months of deaths caused by the plague during the medieval era. The pathogen, Yersinia pestis, of the modern plague performs best in warm and humid conditions.
In “The Black Death: The End of a Paradigm” Cohn says Yersinia pestis operates best at 78 degrees Fahrenheit and 50 percent humidity, but he said the peak July temperature of Florence, where plague ran rampant in the medieval era, was 89 degrees.
Cohn said, “the combination of dryness and high temperature limits flea fertility, cuts short ‘the life of free-wandering fleas,’ and curtails its infectivity. By high temperatures … about 78 degrees Fahrenheit. Above this threshold, ‘plague does not maintain itself in epidemic form’ even with favorable levels of humidity.”
Essentially the pathogen that causes the disease of the modern plague isn’t able to spread at epidemic levels at the times when the medieval plague was the most epidemic.
Wuerth said because of the speed of epidemic, contagion, symptoms, immunity and seasonality, variations of the medieval and modern plague the two are possibly different diseases. The presentation was an enlightening look at the debate of the two plagues.
? The speed of the epidemic is different.
? The contagion, or what causes the plague, is different.
? The symptoms are different.
? There is immunity to the medieval plague, but not the modern plague.
? The seasonality to which the plague occurred is different.