That summer must have been terrifying: between May and October, one in three inhabitants of the area died of plague. Now the study of some papers from 200 years ago tells how the last great plague epidemic in Europe was, the one that struck Mallorca in 1820. From the analysis of newly discovered daily reports of infected and deaths, researchers have been able to calculate its extreme lethality, or point out that the specific form was not bubonic, but pneumonic. But also how, in the absence of antibiotics to fight the disease (which would arrive a century later), confinement measures saved thousands of Mallorcans from death, confining the grim reaper to the eastern end of the island.
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The second plague pandemic, which began with the Black Death at the end of the Middle Ages, ravaged Europe for the next four centuries with periodic outbreaks. The implementation of public health measures, mainly hygiene, managed to expel Yersinia pestis, the causative bacterium, from European territory by the 19th century. One of its last throes was suffered by several Mediterranean islands. In Spain, it was Mallorca’s turn. Legend has it that a shepherd, who picked up the shroud that served as a burial cloth for an infected sailor buried on the island, spread the disease. The real story is now known in full detail thanks to the discovery and analysis of the daily reports sent to the Superior Health Board. Their discoverers have published their results in the scientific journal PNAS.
“It was probably due to smuggling,” says Joana Maria Pujadas-Mora, from the Universitat Oberta de Catalunya (UOC) and co-author of the research. “There was an illegal unloading on a beach near Son Servera [at the eastern end of Mallorca] and the crew of this ship, believed to have come from Tangier, would have been infected,” adds Pujadas-Mora. “Then came the legend of the young shepherd boy as patient zero,” the researcher completes.
While she was already in her postdoctoral stage, her thesis director, Professor of Contemporary History Isabel Moll, from the University of the Balearic Islands, told Pujadas-Mora: “There is a series of deaths, you who work with numbers, look at them, see…” She discovered a treasure, some papers preserved in the archive of the Royal Academy of Medicine of the Balearic Islands that turned out to be a diary of the epidemic. Almost from its beginning, in May 1820, the affected towns had to send Palma a daily report with the number of infected and the number of deaths, both by sex and by age, as well as a situation report. Such was the fear that they disinfected the sheets with vinegar.
It all began, as the legend said, in Son Servera, at the beginning of May, but then spread to neighboring towns. Having the data on total population, number of affected, or number of deaths, with the tools of modern epidemiology, they were able to estimate the mortality rate (deaths over total population) and, more importantly, the fatality rate (deaths over total infected) and other indicators, such as the basic reproduction number, known as R0, unfortunately popularized during the covid pandemic.
“There are three mechanisms of plague transmission,” recalls Pedro Puig, from the Mathematical Research Center (CRM) and the Autonomous University of Barcelona and co-author of the study. “One is by flea or lice bites [vectors after biting a rodent or an infected human]. The development of the disease is slower, and this is when buboes, swollen lymph nodes, appear,” he details. The fatality rate for this type of transmission in the pre-antibiotic era ranged from 30% to 60%. In pneumonic plague, the transmission mechanism is by airborne particles. The third is septicemic [the infection circulates through the blood], which occurs through contact with open wounds or handling of corpses. “In these, the fatality rate is 100%, all die,” Puig completes.
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On average, in the four affected towns, Son Servera, Artà, San Llorenç, and Capdepera, the fatality rate was 78%. “Given such a high observed rate, we believe that both pneumonic and septicemic played a relevant role,” comments Puig. They do not deny the bubonic, but this form does not kill as much. Also, there is the historical detail: Son Servera has no port, so smugglers carried their goods to the coast in small boats from the ship, so it was unlikely that infected rats reached the beach.
The blow was harder where it all started, in Son Servera: of the 1,684 inhabitants the town had, 1,340 were infected. When the epidemic was declared over, in November, only 300 had recovered. Thanks to the vinegar-soaked papers, they were able to estimate an R0 of 1.3 there. It is not as high as the 2.5 estimated for the early days of the covid pandemic, but it was above 1. In nearby Capdepera, the R0 was below. That would explain why in this town, with 1,179 inhabitants in May 1820, only 146 were infected. But R0 is somewhat dynamic, it changes if measures are taken, and measures were taken in Mallorca.
“During covid, they sent us all home. In Mallorca, in 1820, they created a triple sanitary cordon,” recalls Pujadas-Mora. Although at first they did not know what disease it was or the transmitting agent (they even sacrificed all dogs and cats), doctors immediately suspected the plague. So they isolated each of the four affected towns from each other. And these from the rest of the island. Also, within the four towns, they separated the infected from the healthy. They completed it with “a naval blockade; in fact, the area was totally militarized,” points out Puig. The first sanitary cordon already isolated Son Servera on May 27. Inside, almost all died, but outside it was salvation.
Except for one case reported in Manacor, no more were detected outside the isolated area. That is, the other more than 40 towns in Mallorca avoided it. It is one of the lessons that, according to the authors, must be learned: “Although they did not know what they were fighting against, they put sanitary cordons,” highlights Pujadas-Mora. Seeing the dynamics of the epidemic, the researcher is convinced that “it would have reached the whole island and caused very high mortality, so the containment measures were really effective.”
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