From the Diamond Princess to the MV Hondius: International Law Still Lacks Clear Rules for Public Health Emergencies on Cruise Ships

Despite the lessons of COVID-19, the treatment of cruise ships during public health emergencies remains governed by fragmented and incomplete rules under international law. Recent treaty reform efforts failed to resolve the structural gaps exposed both in 2020 and now again in 2026.

In April and May 2026, the expedition cruise vessel MV Hondius became the site of a hantavirus outbreak that has grabbed media headlines across the world. The ship departed Ushuaia, Argentina, on 1 April 2026, carrying around 150 passengers and crew representing 23 nationalities. Passengers were primarily from Spain, France, the United Kingdom, and the United States, while most crew members were from the Philippines.

The outbreak unfolded with tragic consequences. On 11 April, a passenger died on board. His body was taken ashore in Saint Helena on 24 April, where his wife disembarked before dying two days later in a Johannesburg hospital. A third passenger later died on board, and another was evacuated to South Africa in a critical but stable condition.

On 3 May, the vessel docked at Praia, Cabo Verde, but disembarkation was refused due to limited local capacity to manage the emergency. Despite local opposition, Spain eventually agreed to receive the ship in the Canary Islands. On 6 May, three passengers—including the ship’s doctor—were medically evacuated to the Netherlands. After arriving in Tenerife on 10 May, the remaining passengers disembarked and were repatriated, while infected individuals were hospitalised across several countries, including South Africa, the Netherlands, Germany, Saint Helena, Spain, France, and Switzerland.

For many, the events on the Hondius evoked strong memories of the early months of the COVID-19 pandemic. In 2020, cruise ships such as the Diamond Princess and the Ruby Princess became infamous early superspreaders. Many states responded with a mixture of caution and panic, often closing their ports to cruise vessels, leaving passengers and crew stranded at sea.

Recent events revive questions of international law: what responsibilities do port and flag states bear in the event of public health emergencies on cruise ships? When must ships be granted access to ports? How should obligations relating to quarantine, treatment, evacuation, and repatriation be allocated? And, importantly, did the experience of the COVID-19 pandemic provide an opportunity to bring considerations of humanity to the fore when dealing with public health emergencies on cruise ships?

A fragmented legal framework for a transnational problem

The international legal framework applicable to public health emergencies on cruise ships is comprised of a complex constellation of agreements and regimes, including the United Nations Convention on the Law of the Sea (UNCLOS), the International Health Regulations of 2005 (IHR 2005), the Convention on Facilitation of International Maritime Traffic (FAL Convention), the Maritime Labour Convention (MLC) and international human rights treaties.

This framework must account for the inherently transnational nature of cruise shipping and therefore involves overlapping jurisdictions and competing interests: those of flag states, port states, and states whose nationals are on board; those of international organisations such as the World Health Organization (WHO) and the International Maritime Organization (IMO); and those of commercial actors like cruise operators and even individuals such as ship captains.

Public health emergencies at sea expose the tensions inherent in this framework, particularly where capacities and priorities are not aligned.

Port access

One of the most contentious issues—both during COVID-19 and in the Hondius case—is access to ports. Cabo Verde’s refusal to permit disembarkation, as well as the political resistance in the Canary Islands, illustrate the reflex to close ports to ships dealing with the outbreak of disease.

Under UNCLOS, rights and duties concerning port access are largely ignored. As a matter of customary international law, states exercise sovereignty over their ports and may generally deny entry to foreign vessels. Exceptions exist in cases of distress or force majeure, but these are interpreted narrowly.

During the COVID-19 pandemic—and again in 2026—states invoked this sovereign authority to justify port closures and the denial of entry to cruise vessels. These measures were often framed as exercises of border control designed to protect domestic populations from infection.

However, port state sovereignty is not absolute. It is conditioned by other international obligations, notably under the IHR 2005 and the FAL Convention.

The IHR 2005 provide the most directly relevant framework. Article 28 establishes that states should not prevent ships from calling at ports for public health reasons or refuse free pratique, which is the right of ships to enter ports to embark and disembark goods. The FAL Convention extends this principle to cruise ships, providing that entry should not be refused where it would not result in the introduction or spread of disease (Annex, standard 3.20).

Yet these obligations still afford generous discretion to port states. Notably, states may deny entry if they lack the capacity to implement necessary health measures, such as quarantine or disinfection (Article 28(1) of the IHR 2005)—precisely the rationale invoked by Cape Verde. They may also impose inspections and require ships to undertake decontamination measures (Article 28(2)). These exceptions allow port states to prioritise domestic health considerations even at the expense of those on board.

Human rights at sea

Beyond port access, public health emergencies on cruise ships raise significant concerns under the Maritime Labour Convention (MLC) and international human rights law.

The MLC imposes obligations on flag states to ensure that seafarers, including the crew on cruise ships, have access to prompt and adequate medical care on board (Regulation 4.1.3), and requires port states to provide access to medical services ashore where available. It further mandates that onboard medical care should be comparable, as far as possible, to standards on land (Regulation 4.1.4). The COVID-19 pandemic revealed how frequently these standards were not met. Crew members were often stranded for extended periods, denied shore leave, and left without adequate care.

International human rights law adds another layer of protection. All individuals at sea enjoy rights, including the right to health, freedom of movement, and protection from discrimination.

Yet the exercise of public health powers—such as quarantine, movement restrictions, and port closures—can interfere with these rights. During COVID-19 and again in the Hondius case, states faced difficult trade-offs between protecting public health and safeguarding individual rights. The events aboard the Diamond Princess, Ruby Princess, and other vessels during the COVID-19 pandemic revealed structural weaknesses in the international legal framework. While the WHO provides technical guidance, it does not always address how to strike this balance, contributing to inconsistent and, at times, harmful outcomes.

Compounding these issues are enforcement gaps inherent in the law of the sea. Responsibility can be diffused between flag and port states, with each relying on the other to fulfil obligations—sometimes resulting in neither doing so effectively.

The multinational composition of cruise ships further complicates matters. In the Hondius case, many states became involved in evacuation and repatriation efforts of their nationals on board the ship. Diplomatic coordination was required not only to bring nationals home, but also to manage treatment across jurisdictions and conduct contact tracing after disembarkation.

While such efforts demonstrate international cooperation, they also underscore the absence of predefined coordination mechanisms. Much depends on ad hoc arrangements rather than established legal frameworks.

Incomplete reform: the neglect of cruise ships

In the aftermath of COVID-19, states undertook efforts to strengthen global health governance, including through amendments to the IHR 2005 and the adoption of the WHO Pandemic Agreement in 2025. Yet these reforms have largely overlooked the maritime dimension of pandemics—and cruise ships in particular.

This omission is striking and something we have previously warned of. Cruise ships are uniquely vulnerable environments during public health emergencies: contagious disease can spread quickly and ships traversing multiple jurisdiction and carrying people with various nationalities make them dependent on international cooperation between states and non-state actors.

While some changes to the IHR 2005 aim to better balance public health protection with the facilitation of international traffic, they do not adequately address the specific challenges posed by cruise ships. The emphasis remains on the powers of states, rather than on the rights and welfare of individuals on board.

If the lessons of both COVID-19 and the Hondius outbreak are to be taken seriously, more work is to be done.

First, states should develop more specific rules on the treatment of cruise ships during public health emergencies. These should address key issues such as quarantine, medical care, evacuation, and repatriation.

Second, responsibilities must be clearly allocated among relevant actors. This includes not only port and flag states, but also international organisations and private actors such as cruise operators and individuals. Effective responses require coordination, and coordination requires clarity about responsibilities.

Third, reforms should make human rights and humanitarian considerations guiding principles for any response. Public health measures may be essential to prevent further spread of disease, but they must not disproportionately burden those aboard ships. Passengers and crew should not bear all the costs.

Finally, any allocation of responsibilities must take into account the realities of the shipping industry, including the prevalence of flags of convenience. Expectations placed on flag states must be calibrated to align with their actual capacities.

A warning unheeded

The MV Hondius outbreak is not an isolated incident. It is another warning sign—one that echoes the early months of the COVID-19 pandemic.

It demonstrates, once again, the human costs of scrambled health responses at sea. Despite the experience of 2020, international law still lacks clear and coordinated rules for managing public health emergencies on cruise ships. Reform efforts have failed to learn the lessons from the past.

Until cruise ships are properly integrated into the international legal framework, similar incidents are likely to recur. We must learn from our mistakes and place human rights and humanitarian considerations at the centre of the response to outbreaks of disease at sea.

Image credit: fdesroches, CC BY-SA 4.0