The epidemic which struck Venice in 1575 was an outbreak of yersinia pestis — the Black Plague or the Bubonic Plague.
Yersinia pestis is a bacterium, and one of the most virulent diseases known.
It has caused three pandemics in known history. The first was the Justinian plague in the 500s, named after the Byzantine emperor at the time. We don’t have exact numbers, but most likely tens of millions died in and around the Byzantine Empire, and the Italian peninsula was particularly hard hit.
The second pandemic of the plague started in 1348 in Europe, and would over half a century kill half the population of the continent. The plague remained endemic in Europe until the late 1700s, with recurring outbreaks here and there. The epidemic in Venice in 1575–77 was one such outbreak.
Finally, the third and last plague pandemic struck in south-east Asia in the 1890s, and spread through much of South Asia and eastern Africa. Here, too, the victims were tens of millions.
The outbreak in Venice, which Benedetti recounts, is therefore just one of many in Europe over the three and a half centuries the plague haunted the continent.
Infection
The usual way of contracting yersinia pestis is through the blood, most commonly by insect bites. Fleas and mosquitoes were therefore the main carries of the contagion.
The infection has an incubation period of between a few days and a week.
Initially, the bacterium settles in the lymph nodes, in the armpits and in the groin. They swell, and can become the size of chicken eggs. These swollen lymph nodes were often called buboes or tumours.
This phase has given the disease the name Bubonic plague.
If the infected person’s immune system can overcome the infection, it happens at this point. The swelling subsides, the fever falls, and after a while the infection passes, leaving no other marks than the psychological scars.
In the unfortunate case, the infection spreads from the lymph nodes into the blood stream, leading to sepsis. With the infection present all over the body, if the disease doesn’t kill the victim, their own immune system will, as it goes into overdrive and eliminates cells at random.
During the last, fatal phase of the infection, necrosis often sets in. As the body struggles to contain the infection, it sacrifices the extremities, which suffer widespread cell death. Fingers, toes, and sometimes the nose and the lips, go black as necrosis sets in. Death usually follows shortly after.
This last phase has earned yersinia pestis the name Black plague.
The two names are therefore the same disease, but refer to two separate phases of the infection.
Pneumonic plague
It is also possible to contract the plague through the lungs. Infected droplets, from coughs or sneezes of an already infected person, can enter the lungs of another individual.
Pneumonic plague is very fast, and normally always fatal.
Fatality and survival
On average, in the absence of any efficient treatment, between forty and fifty percent of the infected die.
In comparison, untreated COVID-19 has a case fatality rate of one to two percent.
Being a bacterium, yersinia pestis can be treated with antibiotics, as long as it happens in an early stage.
The human body is incapable of developing lasting immunity to yersinia pestis, and it is therefore possible to get it several times. There is, however, some short-term protection, which might be how epidemics like the one in Venice in 1575–77 ran out of steam. Once the bacterium had touched almost everybody, if could no longer find new receptive victims.
Rats and other rodents
We tend to associate the plague with rats.
However, the real vectors of transmission are fleas and mosquitoes. By biting several individuals in term, whether human or animal, they can move minute quantities of blood between them, and with that also the bacterium.
The role of rats and other rodents in the spread of the disease was another.
While humans often die of the plague, many species of rodents don’t. They can live with the bacterium in their blood without getting sick.
It would take a bite of a rat to contract the disease directly from an infected, but otherwise healthy, animal, and such bites are not very common.
The populations of rats, however, served as a reservoir for the bacterium, where it could linger between outbreaks. When, like in Venice in 1577, the bacterium had burned though most of the population, and it failed to find new human victims, it could survive in the blood of the rats, and come back again much later.
Relevance to Benedetti’s account
In the 1500s, people knew none of all this. Their beliefs about the disease are covered in Appendix B.
Benedetti notes that persons returning from the Lazzaretto Vecchio after having survived the ordeal, were sent to clean the houses and belongings of others, who had got sick. They had, therefore, observed that individuals were unlikely to contract the infection again, immediately after having recovered.
Leave a Reply