As the COVID-19 pandemic closes in on a year for many populations around the world, (Gibraltar’s first case was recorded on March 4th, 2020) there has been renewed interest by the public in learning about pandemics of the past.
The 1918 influenza pandemic is considered to be the last ‘Great pandemic’ in our history, because up to fifty million people succumbed to the virus in less than a span of a year. One would speculate that Gibraltar was hard hit by the influenza pandemic over hundred years ago.
This was not the case, in fact epidemics caused by a different virus– yellow fever, resulted in the greatest toll of epidemic deaths of Gibraltarians.
In 1804, yellow fever struck the population with such great force, it is estimated that as many as 4864 or 2300 died. There was no census taken in 1804 but the civilian numbers probably did not exceed 10,000.
The number of deaths during an epidemic has never been observed since. According to Augustin, writing on the history of yellow fever in 1909, 19th century yellow fever epidemics killed more people in Gibraltar and Spain than the yellow fever deaths of all the countries in Europe combined!
The yellow fever epidemics were also unprecedented because the health officials implemented novel and innovative mitigation measures to combat the disease. The development of these measures did not occur overnight, however, but over a course of the four prior epidemics in 1804, 1810, 1813, and 1814.
The large-scale measure, coined the ‘Grand Measure’ by Chief Medical Officer of Health, Dr. John Hennen involved the reduction in the size of the population through the removal of ‘unnecessary’ foreigners, and the placement individuals who had not gone through ‘the fever’ to relocate to the Neutral Ground.
There was also the establishment of the marketplace in the space between the sanitary cordon lines of Gibraltar and Spain, the Pallenque, which was established in 1810 to allow for the safe transfer of goods (these measures are discussed in more detail in a subsequent publication).
Finally, there was certification of having passed through the fever via a fever ticket, which allowed for free movement in and out of the fortress.
Collectively, these strategies were forward thinking for the time because they predated the bacterial revolution of the 1860s, when knowledge about agents of disease began to emerge. Pre-revolution, the most common belief was that diseases were caused by bad air (vapors), known as miasma.
By 1828 in Gibraltar, a contagionist (contact) view for yellow fever transmission predominated; others argued for the influence of the hot weather or the consumption of over ripe fruit.
A Brief Overview of Yellow Fever
Today, we now know that yellow fever (colloquially known as black vomit fever, yellow jack, saffron scourge) is transmitted from human-to-human by means of the biting female mosquito, this intermediate transmitter of the virus is known as a vector.
The onset of symptoms (which can range from mild to severe) occurs within 24 hours. Telltale signs of yellow fever are high temperature, slow pulse, extreme pain, black vomit, and yellow skin.
About half the infected die within a two-week period, and those who survive the fever receive life-long immunity to the virus.
Immunity and the Fever Ticket
When yellow fever struck Gibraltar in the autumn of 1804, virtually all of the civilian population was susceptible, as the virgin soil population, (one with no herd immunity), the disease spread rapidly throughout overcrowded town.
Only with the arrival of the cold weather in December (lack of mosquitoes) and because of the absence of susceptibles, the epidemic finally ended.
When yellow fever reappeared in 1810, authorities were quick to act and immediately moved those who were ill to an encapment at the Neutral Ground. Fortunately, the epidemic claimed only 6 lives.
In 1813 and 1814, yellow fever appeared once again with 640 deaths. By then officials were prepared and implemented many mitigation strategies.
In 1828, yellow fever returned and made its final visit to Gibraltar; 1170 Gibraltarians died. During this epidemic, it was observed (as described in a letter to the editor of The Lancet), that once recovered from the fever the individual was not liable to second attack.
With this knowledge in hand, the health officials introduced the fever passport. Any individual who produced a certificate from an acknowledged medical man, stating that he or she had been infected with the disease in previous epidemic, was allowed by the laws of the garrison to continue to reside in the town, and travel in and out of the Town. Some used the ticket to go to work daily in the Town.
Others used the ticket to enter the Town once a week to retrieve personal belongings. Those who had not passed through the fever had to reside and remain in the encampment at the Neutral Ground.
The photographs of two surviving paper artifacts of immunity passports (with permission from the Gibraltar Museum) for two young individuals presumably from the same family were signed by a local physician. These passports were commonly used in Spain as well.
The Gibraltar immunity passports, however, may perhaps be the earliest surviving examples of its kind, as there is not any documentation of similar passports in the academic literature.
Other health passports originating in 15th century, certified an individual could travel freely because they came from a city free of the disease (Bubonic plague).
And in other contemporaneous locations where yellow fever epidemics were common, such as New Orleans, there was not a formal system for certifying infections.
After the the 1828 epidemic, the newly appointed Principal Medical Officer of Health for Gibraltar, Dr. Pym, noted that because of repeated exposure to yellow fever, Gibraltarians had acquired a high level of herd immunity.
In the Town, 95% had acquired immunity; whereas in the South, only 78% had immunity.
Over two hundred years later, Gibraltar has entered the last phases of the COVID-19 vaccination programme by vaccinating young adults, 20 to 30 years old.
Those who have been vaccinated have been issued cards, and there is discussion for implementation of digital vaccine passports to allow Gibraltarians, not only the freedom of movement in and out of the walls of Gibraltar, but for travel into the European Union and beyond.
About the authors:
Professor Larry Sawchuk is an anthropologist who has been teaching and doing research at the University of Toronto at Scarborough since the 1970s. Professor Sawchuk’s area of interest is population health and the interrelationships between disease, biology, demography, ecology and culture. His work covers the Gibraltar and the Maltese Islands from the 18th Century to present day.
Dr. Lianne Tripp is a biomedical anthropologist whose primary research area focuses on the demography and health of small-scale communities. Lianne’s research has examined inter and intra-population variation of the disease experience in the Maltese islands and Gibraltar. Working with local historians and medical researchers, she has gained considerable insight into the interplay of social and biological determinants of population health of Mediterranean communities. Dr. Tripp is an Assistant Professor at the University of Northern British Columbia.