Mpox, Ebola, Marburg virus disease, Rift Valley fever and avian influenza differ markedly in their reservoirs, transmission routes and clinical impact. Yet a new review identifies a common epidemiological pattern: viral emergence is increasingly shaped by the interaction between animal reservoirs, environmental change, human behaviour and viral adaptation. The authors argue that vaccination alone will not be sufficient and that future preparedness will depend on integrated animal, human and environmental surveillance.
A review published in Vaccines examines some of the major viral zoonoses that have challenged global health systems over the past two decades, including mpox, Ebola virus disease, Marburg virus disease, Rift Valley fever and avian influenza. Rather than treating these infections as separate problems, the authors analyse the ecological and epidemiological mechanisms they share and the preventive strategies that could reduce the risk of future spillover and epidemic amplification.
The review, conducted by researchers from the University of Łódź in Poland, draws on scientific literature published between January 2000 and February 2026. It focuses particularly on the interface between animal reservoirs, environmental pressures, cross-species transmission and vaccination strategies.
Animal reservoirs remain at the centre of viral emergence
One of the central points of the review is that emerging viral zoonoses cannot be understood through human epidemiology alone. The authors note that an estimated 60–75% of known human pathogens and nearly 75% of emerging infectious diseases originate from animal reservoirs. Viral pathogens are especially prone to cross-species transmission because of their capacity for mutation, recombination and rapid adaptation to new hosts.
The pathways leading from an animal reservoir to a human outbreak are nevertheless rarely simple. Spillover events emerge from interactions between wildlife, domestic animals, vectors, human populations and environmental conditions. Land-use change, agricultural intensification, deforestation, wildlife trade and increasing human encroachment into natural habitats all increase opportunities for contact between species that would otherwise interact less frequently.
This is why surveillance confined to human cases often detects an emerging zoonosis only after the virus has already crossed the species barrier.
Avian influenza illustrates the importance of animal surveillance
Highly pathogenic avian influenza provides one of the clearest contemporary examples. Influenza A viruses circulate naturally in wild birds, but their capacity to infect poultry and an increasing number of mammalian species has raised concern over viral adaptation beyond avian hosts.
The review places avian influenza alongside other major emerging zoonoses because its epidemiology demonstrates how rapidly a virus maintained in animals can change its geographical distribution and host range. The continuing global circulation of H5 viruses reinforces the need for surveillance not only in poultry but also in wild birds and mammals. Genomic monitoring becomes particularly important when infections occur in new host species, because it can identify mutations or reassortment events associated with adaptation.
In this context, animal-health surveillance is not simply an agricultural measure. It is part of pandemic preparedness.
Rift Valley fever remains both an animal and human health threat
Rift Valley fever represents a different model of zoonotic emergence. The virus primarily affects livestock, particularly sheep, goats and cattle, where infection can result in high abortion rates and mortality in young animals. Human infections generally arise after contact with infected animals or through mosquito bites.
The disease therefore sits directly at the interface between veterinary health, vector ecology and human exposure. The review highlights Rift Valley fever as an example of a pathogen for which controlling infection in animal populations could substantially reduce the risk to humans.
This distinction is important because vaccination strategies for some zoonoses may need to target the animal reservoir rather than humans alone.
Ebola and Marburg show the limits of reactive outbreak control
Ebola virus disease and Marburg virus disease are associated with very different transmission dynamics once spillover has occurred. Both are linked to animal reservoirs, particularly bats, but outbreaks can subsequently become dominated by person-to-person transmission.
Vaccination has transformed Ebola outbreak control. Ring vaccination (targeting contacts and contacts of contacts around confirmed cases) has become an important intervention during outbreaks where an appropriate vaccine is available. The review identifies targeted vaccination of high-risk populations and ring vaccination as particularly useful strategies for pathogens that produce geographically concentrated outbreaks rather than continuous population-wide transmission.
Marburg virus disease remains more difficult from a preventive perspective because vaccine candidates are still under development and no widely licensed vaccine is available for routine use.
These differences illustrate why a single vaccination strategy cannot be applied to all emerging zoonoses.
Mpox demonstrates how a zoonosis can change its transmission pattern
The global spread of mpox after 2022 provides another example of how zoonotic epidemiology can evolve. Historically, mpox was primarily associated with animal-to-human transmission in parts of Central and West Africa, with limited secondary human transmission. The 2022 multinational outbreak demonstrated that sustained human-to-human transmission could occur on a much larger geographical scale.
The review distinguishes the principal MPXV clades and emphasises the shift from a predominantly zoonotic infection to a situation in which sustained transmission between humans can drive international outbreaks.
Once spillover occurs, the epidemiological behaviour of a virus may no longer be determined solely by its original animal reservoir.
Vaccination needs to be pathogen-specific
A major theme of the paper is that vaccination against zoonoses is not a single intervention. Different epidemiological situations require different strategies.
For some diseases, ring vaccination may be appropriate. For others, vaccination of healthcare workers or other occupationally exposed populations may be more effective. In infections where animals play a central amplifying role, veterinary vaccination may provide the most efficient route to reducing human exposure.
The review highlights the importance of flexible vaccine platforms capable of being adapted rapidly to newly emerging viruses. This is particularly relevant for pathogens whose antigenic characteristics can change rapidly, such as influenza viruses.
The authors also identify equitable vaccine access as a major unresolved issue. Vaccines may exist technically but still fail to prevent outbreaks if they are unavailable where transmission is occurring.
Surveillance is becoming as important as vaccination
Vaccination occupies a central place in the review, but the authors repeatedly return to surveillance. They argue that effective preparedness requires the integration of:
epidemiological surveillance, veterinary surveillance, genomic sequencing and environmental monitoring. Genomic surveillance is particularly important because it allows researchers to reconstruct transmission chains, detect new variants and identify genetic changes potentially associated with altered host range or transmissibility. Digital surveillance systems could complement conventional reporting by accelerating detection of unusual disease patterns.
For animal health, this means that unexplained mortality, reproductive disorders, neurological syndromes or unusual infections in wildlife and domestic animals may provide the first detectable signal of an emerging zoonotic event.
Climate and environmental change alter the conditions for spillover
The review also places viral emergence within a broader environmental context. Climate change can influence vector distribution, wildlife movement and seasonal transmission patterns. Land-use change can alter contacts between wild animals, livestock and people. Agricultural intensification increases animal density and therefore the number of opportunities for viral amplification. These processes do not create zoonotic viruses, but they change the probability that a virus will encounter a new host.
The authors therefore argue that environmental surveillance should not remain separate from infectious-disease preparedness.
New approaches could target transmission before disease occurs
The review also discusses preventive strategies that go beyond conventional vaccination. Among them are transmission-blocking approaches designed to interrupt pathogen movement between hosts and interventions targeting the microbiota of disease vectors.
Research into vector-associated microbiota has expanded because bacteria and other microorganisms living within mosquitoes and other vectors can alter their susceptibility to infection and their capacity to transmit pathogens.
These strategies remain experimental for many zoonotic viruses, but they illustrate a broader shift in prevention: instead of waiting for infection to occur in humans, interventions could increasingly target the ecological mechanisms that allow transmission to happen.
A One Health problem before it becomes a human outbreak
The main message of the review is therefore not that one specific zoonotic virus poses the greatest future threat. It is that the conditions favouring emergence are shared across pathogens.
Animal reservoirs, ecological disruption, vector expansion, human behaviour, international travel and viral adaptation interact continuously. Once these factors align, an infection circulating quietly in animals can move into humans and, in some cases, acquire the capacity for sustained transmission.
The authors consequently place the One Health approach at the centre of future preparedness, integrating human medicine, veterinary medicine and environmental monitoring. For veterinary surveillance, the implication is particularly important. Detecting infection in livestock, wildlife or companion animals is not simply documenting animal disease. In some situations, it may represent the earliest observable stage of an emerging public-health event.
Future pandemic preparedness may therefore depend less on reacting rapidly after human cases appear and more on identifying changes in pathogens before spillover becomes sustained transmission.
Study: Dulska J., Fol M., Druszczynska M. Emerging Viral Zoonoses: Epidemiology, Vaccination Strategies, and Implications for Global Public Health. Vaccines. 2026;14(7):560. DOI: 10.3390/vaccines14070560.
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