What is One Health? A Frontline Defense Against Zoonotic Diseases

When the news broke that bats were the likely source of the virus that spawned the COVID-19 pandemic, a zoonotic disease event that so far has killed seven million people worldwide, many people were surprised. They shouldn’t have been, and public health officials certainly weren’t. That’s because they know that at least 70 percent of emerging infectious diseases that affect humans are zoonotic diseases, which can infect animals and spread to humans and vice versa. The prominence of zoonotic diseases has profound implications for preventing, detecting, and controlling global outbreaks, including the newly dubbed “Disease X” that the World Health Organization (WHO) wants the world to prepare for.

Non-zoonotic diseases are transmitted from human to human. This limited range of hosts for disease creates clear and discrete opportunities for transmission interruption, vaccination, and treatment. Indeed, we’ve been able to eliminate polio in much of the world and dramatically reduced leprosy and measles. Mass vaccination campaigns and surveillance played pivotal roles in the WHO–led global effort that led to a 1980 declaration of eradication of smallpox. It‘s one of the most remarkable successes in public health history.

Zoonotic diseases

Zoonotic diseases such as avian influenza, dengue, and nipah are significantly more challenging to detect and control.

• Complex transmission pathways: Zoonotic diseases are caused by pathogens (bacteria, viruses, and parasites) that can infect both animals and humans. The transmission paths can be complicated. They often involve vectors such as mosquitos or ticks.
• Variety of host species: Zoonotic diseases have a wide range of host species, including wildlife, domestic animals, and livestock, making spillover to humans hard to predict and prevent. This adds complexity to infection prevention control efforts and requires additional layers of surveillance.
• Emerging and Re-Emerging: Zoonotic diseases frequently emerge or re-emerge due to changes in human and animal ecosystems, urbanization, climate, and globalization. The unexpected appearance of the diseases means surveillance must be continuous.

Our solutions, therefore, have to encompass more systems, more variables, and more stakeholders.

One Health Approach

All of these considerations make a One Health approach an indispensable strategy for addressing the multifaceted challenges these diseases pose. What is One Health? It unites and guides the efforts of experts from diverse fields to collectively prevent, detect, and respond to emerging public health threats. It’s an interdisciplinary framework that includes human, animal, and environmental health—and recognizes the interconnectedness of our ecosystems.

One Health can help governments identify root causes of zoonotic disease outbreaks such as ecological imbalances, human-animal interactions, and increasing antimicrobial resistance. In a world where zoonotic diseases can swiftly cross borders and species, One Health strategies stand as a frontline defense, promoting global health security by proactively and comprehensively managing complex and dynamic threats that could lead to disease outbreaks.

Their success is dependent on a number of factors, including:

• Skilled and diverse workforces to surveille, diagnose, control, and recover from existing and currently unknown diseases
• Integrated and interoperable health information systems that make threats visible across ecosystems and enable collective action
• Sustainable health financing that maintains One Health operations
• Governance frameworks that overcome the lack of inherent incentives so that multiple line ministries and subnational actors collaborate in a unified effort

Abt’s portfolio of global health security programs includes a growing number of One Health strategies such as our recently launched partnerships with the Governments of Colombia, Jamaica, Nepal, Kazakhstan, Tajikistan, and Uzbekistan. Our bench of infectious disease experts and our whole-of-systems perspective—understanding how systems interact with each other—enable stakeholders to develop systems-level solutions. Our approach can help strengthen national and subnational human, animal, and environmental health systems—the critical elements for preventing, detecting, and responding to the growing threat of novel animal-human diseases.

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