Pandemic Prevention: Can One Health Reduce Spillover?

What does One Health add to pandemic prevention?

The WHO appeal for an international pandemic agreement cited in recent headline feeds was published on March 20, 2024. It should be understood as background rather than a new announcement. The World Health Assembly subsequently adopted the WHO Pandemic Agreement on May 20, 2025, incorporating One Health into its approach to prevention. That chronology matters when assessing what the original appeal represents. Sources: [WHO's original appeal](https://www.who.int/news/item/20-03-2024-call-for-urgent-agreement-on-international-deal-to-prepare-for-and-prevent-future-pandemics) and [FAO's explanation of the agreement](https://www.fao.org/one-health/highlights/who-pandemic-agreement/en).

The practical issue is how prevention reaches beyond hospitals. FAO explains that the agreement addresses disease drivers where people, animals and ecosystems interact, including environmental monitoring and coordination across health, agricultural and veterinary services. This creates a framework for investigating risks before they become widespread human illness. Its public health value will depend on translating those objectives into functioning services, trained personnel and sustained prevention activities. [FAO's One Health analysis](https://www.fao.org/one-health/highlights/who-pandemic-agreement/en).

How can animal and environmental health affect human infections?

Spillover occurs when a pathogen crosses from an animal into a human. WHO identifies animal trade, livestock farming, habitat fragmentation and encroachment into wild areas among the pressures that can increase opportunities for disease emergence. Its estimate that more than 60% of emerging infectious diseases originate in animals describes the origins of diseases, not the probability that an individual animal encounter will cause infection. WHO, FAO, the World Organisation for Animal Health and the United Nations Environment Programme jointly support the One Health approach. [WHO's One Health fact sheet](https://www.who.int/news-room/fact-sheets/detail/one-health).

The One Health High-Level Expert Panel argues that reducing spillover at its source deserves greater attention alongside outbreak detection and response. The distinction is practical: identifying an infection after someone becomes ill can trigger containment, while reducing hazardous exposure may prevent that initial infection. Prevention therefore requires understanding the particular pathogen, animal population and exposure route involved. The panel's publication is an expert position paper supporting this approach; it does not establish a universal percentage reduction in pandemic risk from any single intervention. [Expert paper on spillover prevention](https://www.who.int/publications/m/item/prevention-of-zoonotic-spillover).

Can new risk indicators predict the next pandemic?

A WHO technical report published on April 17, 2026 describes work with the PREZODE initiative to develop indicators of animal pathogen circulation and human exposure. Using expert-derived information, the researchers found that their indicators correlated with documented avian influenza and MERS coronavirus events. They also used simulations to examine how prevention strategies might change the indicators. This offers a way to investigate whether monitoring tools respond to changes in the underlying conditions for disease emergence. [WHO's technical report](https://www.who.int/southeastasia/publications/i/item/B09677).

Those findings require careful interpretation. Agreement with documented events and performance in simulations do not, by themselves, demonstrate reliable prediction of future outbreaks or prove that an intervention prevents human infections. The practical implication is that these indicators could support decisions about where to investigate risks and direct prevention resources. Demonstrating their real-world value would require prospective evaluation, including whether actions guided by them reduce exposure or illness. The report supports further development of prevention tools, rather than a claim that pandemic forecasting has been solved.