Preparing for Pathogen X: Understanding the drivers of emerging infectious diseases

Prof. David Hayman discusses the pathogens currently on the global risk radar, the drivers of zoonotic spillover and the preparedness gaps that could shape the next pandemic.

As concerns around emerging infectious diseases continue to grow, understanding the drivers of pathogen emergence and the gaps in global preparedness remains critical. From zoonotic spillover and environmental change to climate-driven shifts in disease transmission, a range of interconnected factors are shaping future epidemic and pandemic risks.

We spoke with Prof. David Hayman (Professor of Infectious Disease Ecology, Massey University, and Principal Investigator, Te Pūnaha Matatini, New Zealand), at ESCMID 2026, about the concept of “Pathogen X”, the infectious disease threats currently on the global radar and the practical steps needed to strengthen preparedness, surveillance and prevention efforts worldwide.

Presented at ESCMID 2026: How to prepare for pathogen X emergence: a practical approach. Munich, Germany 17 – 21 April 2026

When preparing for the emergence of “Pathogen X”, which pathogens of concern should currently be highest on the global risk radar, and how helpful is current WHO guidance in prioritizing these threats?

Currently, we should be concerned about Ebola virus disease. However, “Pathogen X” is a useful reminder that the next major epidemic may come from an unexpected source. Preparedness should focus on pathogen groups with known pandemic potential and transmission mechanisms. For example, we know respiratory viruses are a risk, as are vector-borne diseases where common reservoirs exist. That means novel influenza A viruses, including H5N1; coronaviruses related to SARS and MERS; henipaviruses such as Nipah; filoviruses such as Ebola and Marburg; arenaviruses such as Lassa; and arboviruses such as dengue, chikungunya, Rift Valley fever, Oropouche and West Nile virus.

WHO guidance is helpful for prioritizing research and preparedness, but these lists should not be treated as predictions. Their main value is in encouraging adaptable diagnostics, vaccines, surveillance and response platforms. We should be developing systems that are able to cope with and adapt to any type of infection.

How are land-use change, intensive agriculture and the fact that a large proportion of global mammal biomass is livestock influencing the risk of future spillover events?

Land-use change and intensive agriculture disrupt the ecology of infectious diseases. Deforestation, habitat fragmentation and agricultural expansion can bring wildlife, livestock and people into closer contact, creating new opportunities for spillover. Intensive farming may also create large, dense populations of susceptible animals, allowing some pathogens to amplify once introduced.

The fact that livestock represent such a large share of global mammal biomass matters because our food systems are now central to infectious disease ecology. This means livestock are part of “the problem”, although the level of risk depends on land-use planning, biosecurity, animal health surveillance and sustainable production systems.

How do wildlife use, habitat disruption and other forms of environmental change continue to drive zoonotic disease emergence?

Wildlife-associated emergence is rarely caused simply by wildlife being present. Risk increases when human activities change contact patterns between wildlife, livestock and people. Habitat disruption, hunting, trade, logging, mining, agricultural expansion and settlement can all increase risky interfaces.

Environmental change can also favor adaptable reservoir species while reducing biodiversity that may otherwise help regulate transmission. Responses should avoid simplistic blame or blanket bans that harm vulnerable communities. Instead, we need safer wildlife-use practices, stronger surveillance at high-risk interfaces, reduced illegal or high-risk trade and protection of intact ecosystems as part of pandemic prevention.

Climate change is reshaping the spread of vector-borne and infectious diseases. How can One Health approaches be translated into practical surveillance, prevention and response systems?

One Health becomes practical when human, animal, environmental and climate data are linked to action. For vector-borne diseases, this means integrating case surveillance with mosquito or tick surveillance, animal health data, land-use information, weather and climate data, and local knowledge.

Climate change can alter vector ranges, seasonality, pathogen replication and human exposure. Practical systems include climate-informed early warning, genomic surveillance where useful, urban planning that reduces breeding sites, better water and waste management, and clear thresholds for intervention. The key is collaboration before outbreaks occur, not only during emergency response. And, of course, we need to reduce our emissions to limit climate change as much as possible.

Looking ahead to the next pandemic, where are the biggest preparedness gaps today, and what critical risks or blind spots do you think the global community is still missing?

The biggest preparedness gap is implementation. We can do much better, but we continue to lack the support and political commitment needed to do so. Many countries still lack sustained surveillance, diagnostic capacity, genomic sequencing, veterinary public health infrastructure, trained personnel and integrated data systems.

We also remain too reactive, investing more in outbreak response than in prevention. Major blind spots include ecological drivers of emergence, such as land-use change, biodiversity loss, high-risk wildlife trade, livestock intensification and climate disruption. Equity is another critical gap: places where pathogens emerge often have the least access to diagnostics, vaccines and therapeutics.

Future preparedness must be flexible, locally grounded, multisectoral and better connected to upstream prevention.