Expecting the unexpected: the next outbreak will not necessarily look like the last

Two unusual outbreaks in the first half of 2026 have attracted the attention of public health authorities and media alike. Aboard the MV Hondius, a Dutch-flagged expedition vessel returning from South America, a strain of hantavirus produced a cluster of severe illness¹—a seemingly unusual presentation for a group of viruses not generally associated with outbreaks in cruise ship settings. In the Democratic Republic of the Congo (DRC), a rapidly evolving outbreak of Ebola virus disease caused by Bundibugyo virus crossed into Uganda and prompted the World Health Organization (WHO) to declare a public health emergency of international concern (PHEIC).²

Neither outbreak resembles COVID-19, nor should it. Yet both are concerning in their own right, and together they offer an opportunity to reflect on three enduring themes: the need for vigilance against infectious disease threats, the value of international co-operation and co-ordination, and the importance of continuing to strengthen preparedness and response capability.

The nature of emerging infectious disease threats

Much public discussion about emerging infections still tends to view new events through the lens of the last pandemic. The events of 2026 are a useful reminder that infectious disease threats often arise not because they repeat what has come before, but because they challenge existing assumptions.

When reports first emerged of a hantavirus outbreak on a cruise ship, one of our immediate reactions was that the diagnosis might still require confirmation. Hantaviruses are classically associated with exposure to infected rodents and their excreta in remote rural areas, not outbreaks aboard modern sailing vessels. Yet the diagnosis was correct. The virus involved was Andes virus, the one New World hantavirus for which human-to-human transmission, and even super-spreading, has been documented.³ The enclosed environment of the vessel, with prolonged close contact among passengers and crew, created conditions that allowed a known but rarely observed mode of transmission to occur, once an infected passenger had boarded. Nothing here contradicted existing scientific understanding; rather, it combined known facts in an unexpected way.

The Ebola outbreak in the DRC presents a different type of challenge. It is caused by Bundibugyo virus, one of the less commonly encountered Ebola virus species and one that has been responsible for only a small number of recognised human outbreaks since its discovery in Uganda in 2007.⁴ Unlike the more familiar Zaire ebolavirus, there are currently no approved vaccines or specific treatments for Bundibugyo virus infection. Public health authorities must therefore rely heavily on surveillance, contact tracing, infection prevention measures, supportive clinical care and community engagement.

At the same time, the outbreak highlights how much scientific capability has been developed since the 2014–2016 West African Ebola epidemic and the COVID-19 pandemic.^5,6 Genome sequencing, supported through established international co-operation, enabled rapid virus characterisation in both events. Efforts to develop vaccines and other countermeasures against Bundibugyo virus are already underway, drawing on advances in vaccine platforms, clinical trial networks, international collaboration and regulatory processes established during previous global emergencies. While these efforts may not immediately influence the current outbreak, they demonstrate how rapidly scientific responses can now be mobilised when gaps in preparedness are identified.

Together, these outbreaks illustrate an important feature of preparedness: readiness is not just about preparation for a list of known threats. Rather, it is the ability to rapidly recognise and respond when familiar pathogens present in unfamiliar ways, or when known threats expose vulnerabilities that had received relatively little attention. Both outbreaks therefore remind us that preparedness depends as much on adaptability as on anticipation.

The value of the international response system

If the first key theme of these outbreaks concerns the nature of emerging threats, the second concerns the importance of the global systems that exist to detect, assess and respond to emerging infectious diseases.

The outbreak aboard the MV Hondius was, by definition, an international public health event. Passengers and crew dispersed across multiple countries within days, requiring extensive cross-border co-ordination. More than 600 contacts were traced across approximately 32 countries.⁷ With WHO support, public health authorities shared information and resources, aligned case definitions and provided regular situation updates. The overall public health risk was assessed as low, and the event was managed without the need for formal emergency declarations. It provided an example of international public health mechanisms functioning as intended.

The Ebola outbreak presents a different but equally important illustration. Initial reports described a severe febrile illness with high mortality occurring in a remote and insecure region of the DRC where access to healthcare and laboratory services can be challenging, and where the differential diagnosis includes a wide range of infectious diseases with overlapping clinical presentations. Bundibugyo virus was identified by the national reference laboratory in Kinshasa within days of the outbreak being detected by health authorities. Subsequent international support and co-ordination were mobilised through established WHO mechanisms.

These developments highlight the continuing importance of international frameworks such as the International Health Regulations (2005),⁸ which enable countries to share information rapidly, assess risks collectively and co-ordinate responses to events that may transcend national borders. Central to these arrangements is the WHO, whose role in gathering and disseminating information, convening expertise and co-ordinating global responses remains indispensable. That role, however, depends on sustained commitment from member states through active engagement and adequate funding.

The International Health Regulations were amended in 2024 to incorporate lessons learned from the COVID-19 pandemic.⁸ New Zealand has yet to adopt these amendments, a decision that sits against the backdrop of a nation whose health security is linked to the effectiveness of the international system they are intended to strengthen.

At the same time, these outbreaks remind us that even well-functioning systems have limits. The response to the Ebola outbreak continues to unfold in a region affected by poverty, insecurity, population displacement and limited healthcare infrastructure. The first such Ebola outbreak to trigger a PHEIC declaration, in West Africa, lasted more than 2 years and drew considerable international resources in the global response, with the United States of America playing a pivotal role.⁹ Over a decade on, we are operating in the context of global fiscal constraints and major cuts to international aid. Considerable progress has been made, but significant challenges remain. International response mechanisms can mobilise available expertise, resources and attention, but cannot instantly overcome all geopolitical, scientific, logistical or operational constraints.

Acknowledging these challenges is important. The current response appears to have benefited from lessons learned during previous outbreaks, but there is no room for complacency. Emerging infectious disease threats continue to test public health systems in new ways, and ongoing vigilance remains essential.

Preparedness as an ongoing activity

For New Zealand, the implications are clear. Our awareness of distant outbreaks is built largely on information generated elsewhere and shared through international surveillance and reporting systems. Geographic isolation offers some protection, but it does not provide independence from global infectious disease threats.

New Zealand therefore has a strong interest in maintaining the capability to receive, interpret and act upon international signals quickly and effectively. This capability spans public health surveillance, laboratory science, epidemiology, clinical expertise, research, emergency planning and international engagement.

Important initiatives are underway. A national pandemic preparedness programme is being developed¹⁰ and New Zealand has established a national Infectious Diseases Research Platform, hosted by the New Zealand Institute for Public Health and Forensic Science (PHF Science), with a long-term mandate to strengthen infectious disease research capability, support preparedness and develop future scientific leadership.¹¹ The health and research sectors continue to consider lessons from the COVID-19 pandemic, including those identified in the second phase of the Royal Commission of Inquiry into COVID-19 Lessons Learned.¹²

However, preparedness is not a destination that can be reached and set aside. It is necessarily an ongoing process of learning, adaptation, investment and capability development. Emerging infectious disease threats continue to evolve, and maintaining readiness requires sustained attention over time.

The outbreaks of 2026 provide a timely reminder of this reality. A hantavirus outbreak on a cruise ship and a burgeoning Ebola outbreak caused by a virus species lacking licensed vaccines and therapeutics were not scenarios that featured prominently in most preparedness discussions. Yet both demonstrate the same underlying principle: infectious diseases continue to surprise us.

The challenge for all countries, including New Zealand, is therefore not to predict precisely which pathogen will emerge next. Rather, it is to maintain the scientific capability, public health infrastructure, international connections and adaptive capacity needed to recognise and respond effectively when the unexpected occurs. The next outbreak will not necessarily resemble the last. The task, for New Zealand as for every country, is to remain ready for whatever form it takes.