Nils Chr. Stenseth has studied the plague bacterium and the Black Death for 20 years. It came in handy when the corona virus created a global pandemic.
In early December, the authorities in the French city of Marseille marked the 300th anniversary of a major Outbreak of bubonic plague in the city, and Professor Nils Chr. Stenseth of the University of Oslo was one of the speakers - the only non-French speaker. But he did not travel to Marseille; due to the corona pandemic, he instead sat in an office at Blindern and spoke to the French audience via digital transmission.
- In addition to the lectures, we attended a great theater play based on Albert Camus’ novel Bullying. «It was incredible to see that if you had replaced the word »plague« with »corona', this would still have been a relevant and credible story. The two diseases have a lot in common," says Stenseth.
Diseases with similarities
Albert Camus’ novel from 1947 has several levels, for example it has been read as an allegory of the fight against Nazism. But on a concrete level, the novel is about an outbreak of plague in a French colonial town in Algeria. One of the commonalities between the plague and the corona pandemic is that both diseases attack the lungs, and both can be fought with many of the same measures.
- The non-pharmaceutical measures recommended by the health authorities against the corona epidemic were actually «invented» and recommended as early as the Middle Ages as a cure for plague. I'm referring to social distancing, quarantine and stricter hygiene," says Stenseth.
But the plague and the corona are also two completely different diseases, partly because the plague is caused by a bacterium while the corona is caused by a virus - SARS-CoV-2. The plague also has a much higher mortality rate than the corona; so high that an estimated 75 million people died in Western Europe during The Black Death in the middle of the 14th century. The Black Death ravaged Norway in 1349 and 1350. Those infected by the corona virus often become immune to the disease afterwards, while the plague bacterium Yersinia pestis kills people so quickly that it is not possible to develop immunity.
Knowledge about plague and corona
The big one The plague in Marseille from 1720 to 1722 caused around 100,000 deaths and is considered the last major outbreak of bubonic plague in Europe. Professor Nils Chr. Stenseth was invited to speak because he is an internationally recognized researcher in the field, after 20 years of studying the plague and the plague bacterium.
When the virus that caused the ongoing corona pandemic began traveling around the world in February-March 2020, it quickly became clear that Stenseth's plague research was also highly relevant in this new area. It also helped that Stenseth had collaborated for 20 years with researchers in China, where the coronavirus originated.
That's why he's now researching both the plague and the corona, in addition to writing a number of op-eds in Norwegian newspapers in recent months. He is also a contributor to the book «Trust in the age of corona», which was recently published as a collection of lectures under the auspices of the Norwegian Academy of Science and Letters.
Strengthens the theory that the bacterium came to Europe several times
Stenseth's latest scientific article on plague was recently published in the prestigious journal of the American Academy of Sciences (PNAS). In it, he and his colleagues help to put to rest a discussion that has been going on for many years: Were the many outbreaks of plague after the Black Death itself due to the bacterium being present in Western Europe all the time, or did the plague bacterium instead come to Western Europe several times from outside?
- Many researchers have believed that the plague came here only once in recent times, when the Black Death started. They also believe that the bacterium was in some kind of reservoir somewhere in Europe and caused several later outbreaks in Marseille, Porto, Glasgow and Liverpool," says Stenseth.
Professor Stenseth also previously assumed that there must have been a reservoir in Europe. Several research groups had analyzed the genes of plague bacteria found in mass graves from the various outbreaks and found only minor differences. This suggests that all plague bacteria in Western Europe were «close relatives».
In the new PNAS article, Stenseth and colleagues have identified old Yersinia pestis-genome (ancient DNA) that had not previously been discovered. During the fall of 2020, as many as 15 such ancient plague genomes have been published, bringing the total number of known aDNA genomes to 70. A total of 499 different plague genomes are known from our own time.
- If you only look at the genetics, the most natural explanation for the repeated outbreaks in Europe is that the disease was latent in our own continent between the outbreaks. But then there's the question: Does the archaeological, historical and ecological information support that hypothesis? Then the answer is no! If we take an interdisciplinary approach and combine genetic knowledge with these other disciplines, it becomes far more likely that the plague bacterium entered Europe several times," says Stenseth.
Researchers at CEES have shown that the repeated outbreaks of plague in the Middle Ages in Western Europe coincide with the opening of new trade routes to Western Europe from areas east of the Black Sea. The researchers therefore believe that it was not only fur and leather and other useful goods that were transported from the east - but also probably plague and death.
The plague came from the east
The Justinian plague which struck the Eastern Roman Empire in 541-542 AD, is considered to have been the first pandemic caused by the bacterium Yersinia pestis. Between 40 and 50 percent of the population is believed to have lost their lives in the affected areas.
The Black Death in the 14th century is considered the second Western European plague pandemic. The interdisciplinary research shows that this pandemic came to Western Europe via Russia, from an area of origin in Central Asia.
The third Western European pandemic caused by Yersinia pestis started in the mid-19th century and ebbed in Europe around 1950, but is still going on in other parts of the world. "There is every reason to assume that this new infection came to Western Europe via the areas around Turkey and Georgia," says Stenseth.
The climate affects the risk of infection
The research has now shown that the plague bacterium normally lives in the intestines of fleas that feed on the blood of wild rodents on the steppes of Central Asia. At the beginning of 2015, Stenseth and his research colleagues found a link between the climate in this region and outbreaks of plague in humans.
The changeable climate in Central Asia can cause some summers to be hot and humid with increased plant growth, leading to an increase in the rodent population because the food supply is so good. It also leads to a much larger population of the fleas that feed on the rodents, and the same goes for Yersinia-bacteria that live in the fleas.
But after a couple of years, the climate may become cold and dry, and plant growth is reduced. This in turn leads to the rodents having less food, causing rodent populations to decline or collapse completely. This creates a «housing shortage» among the fleas, which start looking for other hosts to suck blood from - such as pets and humans. And once humans - and their livestock - in Central Asia have been infected, the bacteria can spread further.
- "We found no correlation between the climate in Western Europe and outbreaks of plague in our part of the world. But we did find a connection between the outbreaks of plague and the climate in Central Asia," summarizes Stenseth.
The corona virus from bats
In the Middle Ages, the plague bacterium spread along trade routes that brought animal fur from the East to Western Europe, but today it is mainly air travel and tourism that have caused the coronavirus to spread across large parts of the world. Professor Stenseth has had a large supply of data from Chinese colleagues since the outbreak of the corona pandemic, and he was one of the first to warn that we can expect more such pandemics in the future.
- It is now very clear that this virus originated in the Wuhan area of China, and that it was originally a virus that lived in bats. It is still unclear whether the virus was transmitted directly from bats to humans, or whether it was transmitted via another animal.
- There is no evidence to suggest that the infection was transmitted from animals to humans at these much-discussed wet markets; it is more likely that the transmission must have occurred in the wild. But there is good reason to assume that the wet markets functioned as these sports bars where people who were on skiing holidays in Austria were infected: There are a lot of people who are very close to each other, which makes it easy for the virus to spread from person to person," says Stenseth.
Immunity in Africa
At the start of the corona pandemic, many people were worried about what would happen when the virus came to Africa, with many poor countries and poorly developed healthcare systems. But now the figures show that The death rate in Africa is lower than in other parts of the world. Why is this the case?
- It turns out that there was an outbreak of a COVID-19-like virus in the continent a few years ago. This virus caused relatively mild symptoms, but it seems to have meant that large parts of the African population still have antibodies that partially protect some against the ongoing pandemic. This is at least one of the reasons why the virus has been much milder in Africa than in other parts of the world," says Stenseth.
- There are also several other factors that come into play. Among other things, Africa has a younger population than, for example, Western Europe and the United States, and the climate in large parts of Africa can be unfavorable for this virus. In addition, the authorities in many African countries were quick to introduce infection control measures," explains Stenseth.
Historical lessons can be applied today
When Professor Stenseth gave his lecture at the Academy of Science, he focused on the fact that studies of the medieval plague can teach us a lot about the corona pandemic.
- The most important lesson from the nineteenth-century plague epidemic that we can use to combat the corona pandemic is that the measures - such as entry bans and quarantines - must be introduced quickly. Everyone must practice good hygiene and use disinfectants. We must encourage people to follow the advice given by the authorities, and we must avoid major local or national differences. It's important to think globally and act locally," says Stenseth.
- "In the wake of the corona pandemic, we should bring together researchers and other partners for a conference, just as major plague conferences were held in Vienna in 1897 and in Manchuria in 1911. On that basis, we can establish an international, joint, knowledge-based pandemic strategy," he adds.
Professor Stenseth also finds it sad that the world's politicians did not listen to the warnings that came long before the corona pandemic broke out. One of those who warned was Gro Harlem Brundtland, former head of the World Health Organization (WHO), who in 2018 to 2019 led the work on a report documenting that what is now happening is a predicted disaster.
Take better care of nature
Stenseth also emphasizes that we should listen to the UN's Panel on Nature, which has warned that we are about to affect nature in a way that increases the risk of frequent and severe pandemics in the future.
- The transmission of the coronavirus from bats to humans almost certainly occurred in the wild. It is also the case that the people who fall ill with plague in Inner Mongolia today are infected in the wild. The violent fragmentation of nature that is going on today leads to the formation of wild nature cores near large crowds of people, which is why the risk of pandemics is increasing. We need to start taking better care of our nature," summarizes Stenseth.
