Fighting pandemics with One Health
The current Corona pandemic shows: Human health is related to animal health and the environment. Only by understanding this unity in terms of "One Health" we will be able to prevent future pandemics.
Josef Settele still remembers the controversy over the face masks clearly: Ten years ago, the biologist from the Helmholtz Center for Environmental Research (UFZ) had written an essay with colleagues on a pandemic scenario. "It was intended purely as a thought experiment, as a shock scenario," Settele says today. To illustrate the point he suggested a photo of people wearing masks. "The publisher tried to talk me out of the idea, saying it was far too bleak to assume that people all over the world were walking around in masks. Today I'm glad I insisted on that photo back then."
Josef Settele is a biodiversity specialist and has been involved in biodiversity conservation for many years. At readings, guest lectures and award ceremonies, or in front of the federal cabinet, he patiently explains time and again that species extinction, the climate crisis and the threat of pandemics are three catastrophes that fuel each other. "Most audiences are completely surprised when they hear about what links disease outbreaks to biodiversity." Settele then usually chooses a highly simplified three-step explanation to explain the connections: "When we destroy forests, we create fantastic conditions for a few species. These species reproduce strongly and diseases spread quickly in these dense populations. If humans then also interact with them, for example, as livestock farmers or as hunters, the diseases can jump to them." Rapidly, pathogens then continue to spread thanks to globalization, as was likely the case with Covid-19.
Scientists have known about the connections for some time: The realization that human health is causally linked to a healthy planet and healthy animals led to the creation of a branch of research called "One Health" several years ago.
"Everyone defines it a little differently, and some prefer to call it 'Planetary Health,'" says Fabian Leendertz, "but the core content is the same everywhere." Leendertz is a veterinarian and founding director of the Helmholtz Institute for One Health, which is currently being established in Greifswald, one of the first institutions ever to address this topic decidedly. "We want to become a hub to link expertise from very different research areas," he says.
Leendertz himself has specialized for decades in zoonoses; diseases that jump from animals to humans, or vice versa from humans to animals. "More than half of the known pathogens are zoonotic," says the veterinary medicine graduate. Measles, for example: According to the latest findings, they jumped from cattle to humans 500 years before Christ. Or corona viruses: They spread in animals long before the current pandemic and then became a human disease. The same applies to AIDS and Ebola. "The species barrier actually works very well," says Fabian Leendertz. "The hurdle for transmission is very high, even higher for viruses, which first have to dock with human cells, than for bacteria.
But momentous coincidences do occur time and again." This is where the climate crisis comes into play again: If a bat with dangerous viruses lives isolated in the deep jungle, the risk of transmission is initially low. However, the closer humans get to it, as forests are cut down or dry up, the greater the potential points of contact become. Another example: When people can no longer keep livestock because of animal diseases or unfavorable climatic conditions, they get the meat out of the forest by hunting, and in the process come close to fruit bats, bats and rodents that have lived largely unmolested by humans for centuries.
Claudia Traidl-Hoffmann has a completely different view of the connections. She heads the Institute of Environmental Medicine at Helmholtz Munich and serves as chief physician at the University Hospital in Augsburg. In her consultations, she sees what climate change is doing to people, even in our latitudes: There are patients who suffer from hay fever as early as January and are bitten by ticks in March because seasons are shifting more and more. There are more and more patients who are hospitalized with various diagnoses during and shortly after heat waves, or physician colleagues who notice increased symptoms of mental illness or many strokes during certain weather conditions. "Healthy people only exist on a healthy earth," says Claudia Traidl-Hoffmann, "but even so, environmental medicine is still a very new discipline that doesn't even exist at all university hospitals." With its 50 staff members, she conducts basic research in this field. The composition of the research group also illustrates how many aspects play into the One Health issue: "There are only three physicians in our team. The others are biochemists, meteorologists, nutritionists, aerobiologists and lawyers, for example." The consequences of climate change on human health are so complex that doctors have long since been unable to get anywhere in research on their own.
Was genau ist der One Health-Ansatz?
The major changes are also the subject of Annette Peters: The epidemiologist heads the Institute of Epidemiology at Helmholtz Munich and is also a specialist in large, long-term population studies. The NAKO health study, for example, is being conducted under her leadership: A study in which more than 200,000 subjects are repeatedly examined over many years. Environmental factors are also recorded, so their influence on human health can be studied over many years.
And the deeper the researchers delve into the web of side effects and interactions, the more connections they discover. It's like measuring the world all over again, says Annette Peters: "In our cohort studies, we always collect data very close to the individual. Now we're zooming away from the individual and taking a wide-angle look at the overall state of the planet. We're looking at the factors that influence human health and then shifting the focus back to the individual." The complex interrelationships are now also being increasingly taken up by policymakers, for example, through the limits on air pollutants set by the WHO, which often find their way into national legislation.
One can imagine the One Health researchers sitting in front of a huge puzzle, whose individual pieces they are gradually putting together. And each of them is working on a different end of the big picture that is emerging piece by piece. Fabian Leendertz, for example, a veterinarian and founding director of the Greifswald Institute, is working with his colleagues to organize One Health surveillance: Using samples of human and animal biomaterial, which they collect at regular intervals both in Mecklenburg-Vorpommern and in Africa and then archive, the aim is to enable long-term monitoring of pathogens and their spread. Fabian Leendertz explains that this study can be thought of as similar to a weather station for stored meteorological data. With his team, he is working with local partners in Africa to build up solid know-how on the ground so that colleagues there can respond more quickly to emerging zoonoses, for example. "Collaboration among researchers worldwide is more important than ever," Leendertz emphasizes.
And Josef Settele, the biodiversity expert from the UFZ, is also focusing on networking and education. "Just as the three major crises; species extinction, climate change, and pandemics fuel each other, they can also be combated together," Settele is convinced. "Everyone can make a contribution to this, from their personal mobility behavior to designing their garden as an insect paradise." The biologist has a level-headed view of the subject. He has no fears for nature, which always adapts well to new conditions, says Settele: "The only question is what role we humans will play in the future." To find a positive answer to this question, the One Health specialists are working together; joining forces in the search for solutions for people, animals and the climate.