The COVID-19 pandemic has shown that zoonotic diseases – infections that pass from animals to humans – can pose enormous threats to global health. More than 70% of new and re-emerging pathogens are derived from animals. It probably includes the SARS CoV-2 virus, which scientists largely believe originates from bats.
There are still questions about specifically where the SARS-CoV-2 virus originated. But experts across the globe agree that communities can take steps to reduce the risk of future contagions. One key is that veterinarians, doctors and scientists work together and recognize how closely human health is associated with animals and the habitats we share – an approach known as One Health.
To prevent new pandemics, researchers need to identify specific sites where viruses are most likely to jump from animals to humans. In turn, this requires an understanding of how human behavior – from deforestation to burning fossil fuels to conflict to cultural activities – contributes to contagious risks.
We focus on global One Health research and education and the epidemiology of infectious diseases, and we served in a scientific task force convened by the Harvard TH Chan School of Public Health and the Harvard Global Health Institute to evaluate current knowledge on how to prevent transmission. The Task Force’s report noted that a recent analysis estimates the cost of dealing with high-risk interfaces through One Health approaches and forest conservation at US $ 22 billion to $ 31 billion per year. These costs are overshadowed by the estimated global GDP loss of nearly $ 4 trillion in 2020 due to the COVID-19 pandemic.
In our view, coordinated investment based on a One Health approach is needed to initiate and maintain global prevention strategies and avoid the devastating costs of pandemic response.
Recognize risk zones
It is challenging to identify areas with a high risk of zoonotic infection. Humans and wildlife move around a lot, and exposure may not immediately lead to infection or cause symptoms that clearly reflect exposure to pathogens.
However, researchers can make predictions by combining data on human and livestock density with data on environmental conditions, such as deforestation and land use change, that could allow pathogens to spread from wildlife to humans. For example, there are areas in China, Indonesia, India and Bangladesh where development has fragmented forests and expanded animal husbandry and human communities near the natural habitat of the horseshoe bat. This group of bats, which includes more than 100 species, has been implicated as a reservoir for many coronaviruses.
It is not uncommon for bat-borne diseases to spread to humans. Sometimes it happens directly: for example, bats in Bangladesh have repeatedly transmitted the Nipah virus to humans. Or the pathogen can move indirectly via intermediate hosts. For example, bats in Australia in 1994 infected horses with the Hendra virus, a respiratory disease that then spread to humans.
In Brazil, yellow fever is endemic in the jungle, mainly spread between monkeys via mosquitoes. People in the country get it from time to time due to mosquito bites, and deforestation and land conversion to agriculture increase the risk of greater contagion. There is growing concern that the disease may be introduced in Brazil’s major cities, where Aedes aegypti mosquitoes are widespread and can transmit it on a large scale.
There is also specific human behavior that can further increase the risk of infection. They include work that puts people in direct contact with or near animals, such as harvesting bat guano (manure) for manure and buying and selling wild animals or animal parts.
Daily routines related to storing food and eating meat from wild animals can also create risks. For example, outbreaks of Ebola virus in Nigeria have been linked to the slaughter and eating of bushmeat.
People in high-risk areas of infection do not have to stop living their lives. However, they need to recognize that some actions are more risky than others and take appropriate safety precautions, such as wearing protective equipment and making sure the bushmeat is handled and cooked properly.
The importance of teamwork
In our view, it is essential for researchers and governments to understand and embrace the central concept that animal, human, and environmental health are closely linked, and factors that affect one can affect everyone. Ideally, problem-solving teams are formed that address prevention from community and district levels to the ranks of health, animal and environmental ministries.
Community members are most likely to know where humans are most at risk of coming into contact with animals that can carry infectious diseases. By listening to them, veterinary and health professionals, as well as foresters and land managers, can develop strategies that are more likely to reduce the risk of contagion.
Organizations such as the US Agency for International Development, Food and Agriculture Organization of the United Nations, national governments and civil society groups invest in One Health platforms across selected countries in Africa and Asia. These networks are typically anchored in ministries. They may also include non-governmental organizations and civil society groups committed to promoting health and well-being through a One Health framework.
For example, many countries have separate databases to track outbreaks of infectious diseases in humans and animals. Connecting these systems across ministries and agencies can improve the exchange of information between them and lead to a better understanding of contagious risks.
We believe that preparations for the next pandemic must include prevention at its source. Our best chance of success is to coordinate research and design of contagion interventions in recognition that the health of humans, animals and nature are intertwined.
New report from Harvard and global experts shows that investment in nature is needed to stop the next pandemic
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