Public health in action: from detection to response – how International Health Regulations (2005) guided response to hantavirus outbreak
In a world where people can cross borders in minutes, an infectious disease event – such as the cluster of hantavirus cases on the MV Hondius cruise ship – can quickly become a multi-country challenge.
The International Health Regulations (2005) (IHR) are the legally binding global framework that obligates countries to prevent, prepare for, detect, report and respond to public health threats that cross borders.
When the United Kingdom notified WHO on 2 May 2026 of a cluster of severe respiratory illness cases aboard a Netherlands-flagged cruise ship in the Atlantic, passengers from 23 countries were on board. Within days, cases of hantavirus (Andes strain) had been confirmed in the Netherlands, South Africa and Switzerland. The ship was still at sea.
What followed was one of the most complex multi-country outbreak responses in recent years – and a direct test of the IHR.
WHO staff deployed to the response view the MV Hondius on the horizon. WHO, partners and authorities supported and coordinated operations in the Port of Granadilla, Tenerife, Spain, on 10 May 2026.
Preparedness
Under the IHR, countries are legally obligated to designate points of entry, including international airports and ports, and to develop, strengthen and maintain specific core public health capacities to prevent, detect and respond to health threats. This selection is based on risk assessments, traffic volume, and the need to manage the health risks associated with international travel and trade. Preparedness is key.
The complexities of the hantavirus cluster detected on a cruise ship demonstrate why the IHR are the backbone of international outbreak coordination and response, underlining the importance of global cooperation and solidarity in tackling health threats that know no borders.
A WHO team of international health experts analyse information on the cluster of hantavirus cases.
24/7 surveillance, detection and notification
From the moment that WHO is notified of a public health threat, IHR National Focal Points (IHR NFPs) and WHO engage in rapid, structured cross-border information exchange. This allows countries to share information quickly and work with WHO to ensure established procedures are followed.
In 2025 alone, the regional WHO team screened 224 000 pieces of information from both official sources, including the IHR, and media articles, resulting in 116 major public health events identified, of which 70 required immediate WHO operational response and follow-up.
Speed matters: on a ship where passengers live in close quarters and then disperse to different countries, every hour of delay adds to the contact tracing challenges.
On 2 May 2026, the United Kingdom’s IHR NFP notified WHO of a cluster of undiagnosed severe acute respiratory illness cases, on board the HV Hondius.
“The IHR provides clear rules and processes for reporting and managing health risks, so everyone knows what to do during a crisis, and encourages and supports countries to strengthen their own health systems, so they are better able to detect and respond to outbreaks,” said Demi Reurings, IHR NFP for the Netherlands.
Spanish authorities view the disembarkation of people from the MV Hondius.
Risk assessment, guidance and recommendations
While the ship was still anchored off Cabo Verde, a WHO health emergency officer from the Regional Office for Africa boarded and was joined by 2 doctors from the Netherlands and an expert from the European Centre for Disease Prevention and Control (ECDC). They conducted a rapid epidemiological investigation, assessed everyone on board, and confined passengers to their cabins while symptomatic individuals were immediately isolated.
Meanwhile WHO initiated outbreak investigations and developed guidance documents for the disembarkation and onward management of passengers, and the management of contacts ahead of their arrival in Tenerife, Spain.
These were promptly shared with IHR NFPs. “During acute public health events, Member States need timely, practical, evidence-based guidance. We work closely with ECDC and national authorities to translate the latest scientific evidence and past experiences into actionable advice, and then rapidly share information through established IHR channels,” said Kareena Hundal, WHO IHR Contact Point, European Region.
Passengers being evacuated from the MV Hondius as part of the emergency response operation.
Medical evacuations
When patients need care that is not available locally, countries can coordinate time-sensitive medical evacuation and safe clinical reception.
WHO engaged with the shipping company and national authorities to facilitate 2 medical evacuation flights to the Netherlands, transferring 2 confirmed cases directly to specialist hospitals in the Netherlands; 1 high-risk contact was transported on to Germany. This is a practical demonstration of what the IHR makes possible: time-sensitive patient transfer across borders while reducing onward exposure.
In parallel, WHO facilitated repatriation flights with the European Union and ensured a critical patient transfer service provider was on standby in case any passenger or crew member developed symptoms and required urgent medical evacuation.
Passengers and crew being evacuated from the MV Hondius as part of the emergency response operation. Port of Granadilla, Tenerife, Spain, 11 May 2026.
Contact tracing
During travel-related outbreaks, WHO and countries support international contact tracing through IHR coordination, linking clinical detection to public health follow-up across borders. During the hantavirus response, the IHR NFP for the Netherlands and the conveyance operator informed 12 countries whose nationals had disembarked earlier at Saint Helena, as well as the public through the WHO Disease Outbreak News portal. That notification led directly to the identification of a case in Zurich on 6 May.
Contact tracing documents exposure, enables timely care and helps contain spread.
“People on the cruise ship came from all over the world, and they returned to countries from all over the world. So, following them has been a massive multi-national cooperation feat. The ability of all the governments to come together and follow up on those contacts to make sure that nobody else gets sick has actually been amazing,” said Boris Pavlin, WHO epidemiologist.
WHO, partners and Spanish authorities support the coordination and response operations in Port of Granadilla, Tenerife, Spain, on 10 May 2026.
Coordination
Laboratory testing in South Africa confirmed hantavirus infection in a critically ill patient who was on the boat days before.
WHO coordinated a rapid, multi-country effort involving laboratories across several nations to sequence and analyse Andes virus genomes from the cruise ship cluster. By standardizing sequencing methods, comparing results and distinguishing real mutations from technical noise, scientists established how the cluster originated and spread on the ship.
“This analysis – published on 10 May – turns multi-country laboratory data into actionable public health intelligence to guide quarantine protocols, medical evacuations and international contact tracing. This coordinated response exemplifies Article 44 of the IHR (2005), which encourages State Parties to collaborate in detecting, assessing and responding to public health events, with WHO facilitating technical cooperation and logistical support across regional networks and international bodies,” Karen Nahapetyan, Laboratory Specialist, WHO/Europe.
WHO Infection, Prevention and Control Officer, Dr Ana Paula Coutinho Rehse, Port of Granadilla, Tenerife, Spain, 10 May 2026.
Disembarkation in Tenerife
When a port is not equipped to apply necessary health measures, a ship may be directed to proceed to the nearest suitable port if needed. This helps ensure the ship can be managed where appropriate capacities exist, while protecting port communities.
Before the ship arrived in Tenerife on 10 May, WHO provided Spanish authorities with step-by-step operational guidance for the safe disembarkation and onward management of all passengers and crew – covering infection prevention, screening advice and risk communication.
“The guidance contained advice on public health measures – including for application on board, as well as during disembarkation or medical evacuation, and risk communication messaging and screening advice for passengers and crew members,” said Ana Paula Coutinho Rehse.
Twenty-three countries were involved in the operation. All passengers have since returned home and are under 42-day monitoring, according to WHO recommendations.
WHO also supported authorities and the conveyance operator in coordinating public health measures for crew members remaining on board after passenger disembarkation, including isolation arrangements, health monitoring, collaboration with health personnel on board and safe continuation of essential ship operations.
WHO Director-General Dr Tedros Adhanom Ghebreyesus and Minister of Health of Spain Mónica García Gómez attend a press conference to share updates on ongoing hantavirus operations.
“Solidarity is our best immunity”
Regular information updates to the public as the situation evolved, targeted risk communication and real-time social listening sought to address people’s concerns, counter false information, and ensure that individuals and communities had accurate, timely advice needed to make informed decisions about protecting their health.
“Twenty-three countries have been involved in the evacuation of people from the boat. We are in coordination with other international sanitary authorities to do this with all possible security and the greatest safety guarantees for the population and for public health,” commented Minister Gómez, at the disembarkation of passengers in Tenerife.
“This outbreak reminds us that health security is not built during a crisis – it’s built before one,” said Dr Hans Henri P. Kluge, WHO Regional Director for Europe. “The IHR gave us the framework. Collective action gave us the response.”
“While this is a serious incident, WHO assesses the public health risk as low. It also shows why the International Health Regulations exist, and how they work,” said Dr Tedros. “I think we should be strong believers in solidarity because that’s our best immunity. It’s only when we support each other that we can respond effectively to viruses or outbreaks like this.”
The hantavirus cluster on the MV Hondius is the first documented outbreak of this virus on a ship. It is unlikely to be the last time that a pathogen tests the international health architecture at sea.
The response demonstrated that when countries notify quickly, share data openly and act in solidarity, the system holds and lives are saved.