London School of Hygiene & Tropical Medicine

The evolving outbreak

In early May 2026, the World Health Organization (WHO) confirmed an outbreak of hantavirus on an Atlantic cruise ship that was travelling from Argentina to Cabo Verde. The outbreak has continued to develop since, with the WHO confirming the type of hantavirus involved in the outbreak as the Andes virus. A WHO case update on the 13 May reported 11 cases in total, with three deaths. Eight of these cases were laboratory-confirmed for Andes virus infection, two are probable, and one case remains inconclusive and undergoing further testing.

LSHTM experts have been providing independent analysis and commentary on the outbreak from the beginning, with Roger Hewson, a Professor in Molecular Virology providing a rapid reaction as the outbreak unfolded on 4 May. Similarly, Professor Michael Marks outlined how the virus spread is different to that of COVID-19 or flu and Professor Damien Tully explained how rapid sequencing of virus strains provides valuable early clues to help with outbreak response.

The next pandemic

Has hantavirus ever been identified as a type of virus that could cause a future pandemic?

In its current form, the Andes hantavirus causing the 2026 outbreak is unlikely to cause a global pandemic as it does not spread easily between humans and requires close contact with the infected person.

However, the virus family (Hantaviridae) does feature on the 2024 World Health Organization’s Priority Pathogen list as a precaution, given other hantaviruses can cause serious illness and fatalities. As such, there is a risk that, following a change in hantavirus’ structure through genetic mutation, it could become more easily transmissible between humans and thus a pandemic risk. There is, however, no evidence of this from other previous hantavirus outbreaks, nor from this current outbreak.

Can we expect more frequent outbreaks of hantavirus and similar zoonotic diseases in the future? What factors could increase this risk?

For hantaviruses specifically, it remains unclear what contribution climate change is having or will have on potential future outbreaks. However, hantaviruses are known to be climate sensitive, so there is the potential for climate change to influence their epidemiology, including their distributions and impacts on people. There are several factors that will play a role in determining this; climate characteristics, habitat loss, land-use and the distribution of people.

Climate characteristics and climate change may directly influence the presence or abundance of hantavirus reservoir host species, which are typically rodents. For instance, a change in rainfall patterns due to climate change could influence rodent reproductive patterns which could in turn impact their population abundance and human exposure risk.

Habitat loss, destruction or degradation can both directly and indirectly influence disease transmission. In areas where animals that can carry diseases that spread to people (zoonotic hosts) are found, removal of vegetation or other destructive activities (e.g., road building) can mobilise infectious pathogens. Hantavirus infections for instance are often caused by people disturbing areas where rodents live. Since hantavirus is shed in their droppings and urine and can persist in the environment for some time, the disturbance can aerosolize the pathogen, exposing people in the vicinity who may breathe it in to become infected.

Another important aspect is how climate and habitat and their changes influence the distribution and behaviour of people, which in turn influences disease exposure patterns. For instance, zoonotic transmission requires contact or close association between people and animal hosts or vectors. Since climate can influence when, where and what people do in certain places, this can help shape exposure patterns. Similarly, land use activities (e.g., agriculture and infrastructure development) are associated with the presence and density of people in different landscapes where disease carrying species may also occur.

Outbreak response in action

There is now a constant trickle of people being asked to self-isolate, is this a sign of a wider outbreak or just the outbreak response system working as expected?

The system is working well and, as it should, the WHO and Africa CDC have already implemented precautionary containment measures.

As per the International Health Regulations, the WHO was first informed on 2^nd May 2026 of severe respiratory illness cases aboard MV Hondius, a cruise ship. This notification led to the global public health response system kicking into high gear, with the outbreak being managed through a coordinated international response, including in-depth epidemiological investigations, case isolation and clinical management, medical evacuations, laboratory testing and international contact tracing, quarantining and monitoring.

On the outside, it looks like cases keep cropping up but this is likely due to the fact that individuals infected with the virus, and those who have been in close contact with them, can develop symptoms anytime between one and eight weeks after exposure. Importantly however, the global public health system can cope with this as there is ongoing follow-up and contact tracing of direct cases and their close contacts by local health authorities in respective countries to prevent further disease spread.

Furthermore, the WHO is following best practice by regularly updating public health recommendations as “additional epidemiological and laboratory evidence, including genetic sequencing data, becomes available” so that both public health experts and the general public know the latest details as the outbreak changes.

Are there any previous examples of outbreaks on cruise ships? How were they managed?

Disease outbreaks on cruise ships are relatively common and are usually well contained without causing further spread or global pandemics. It is important to stress that cruise ships are safe and enjoyed regularly by many holidaymakers but, due to their enclosed physical spaces in cabins and regular close contact between passengers and crew, they can sometimes provide the right conditions for diseases like norovirus and flu to spread easily and quickly.

In the case of this hantavirus outbreak, based on currently available information, the WHO’s working hypothesis is that the index case first acquired the infection prior to boarding the cruise ship, through exposure on land while subsequent infections likely occurred among close contacts once aboard.

The pandemic preparedness landscape

Should we be using this as an example of why the Pandemic Agreement is so important and that there should be continued funding for pandemic preparedness?

This outbreak is a clear example of the benefits of global information sharing, with LSHTM’s  Dr Damien Tully of the MRC/UVRI & LSHTM Uganda Research Unit highlighting that the genome of the Andes hantavirus identified in this outbreak was publicly shared within days of the first widely reported case, providing a valuable early signal to help with managing the outbreak.

This type of data sharing is vital to ensure a smooth and orderly global public health response both during emergencies like a disease outbreak and in normal times. For example, genomic sequence sharing is common practice with flu viruses throughout the year, allowing public health professionals to determine what types of flu might come up in the next flu season to and design effective vaccines against those strains.

That’s why, from a scientific perspective, countries ratifying the WHO’s Pandemic Agreement, particularly the Pathogen Access and Benefit-Sharing (PABS) System clause, is vitally important to ensure effective global health responses. The hope is that PABS will enshrine a requirement that data sharing continues openly between signatory countries based on public health needs, thereby strengthening and expanding pandemic prevention, preparedness and response capacities globally.

How has the change to global public health funding, particularly the US’s role, affected how the World Health Organization has tackled this outbreak? What could it mean for future disease outbreaks?

There is no denying that the global public health funding landscape has changed, particularly with the US withdrawal from the WHO which has directly affected its funding. However, it is not a death knell for global public health, rather an opportunity for other WHO Member States to step up and contribute, not only monetarily but also through technical expertise and logistics to ensure the WHO can still effectively respond to public health emergencies.

Encouragingly, in the case of this hantavirus outbreak, this “stepping up” is already happening, with Spain’s Prime Minister allowing the cruise ship to dock and disembark passengers in Tenerife. This action was applauded by WHO Director-General Dr Tedros Ghebreyesus: “I thank Prime Minister Sánchez not only for meeting Spain’s legal duty under international law, but also for exercising his moral duty to show solidarity with, and compassion and kindness for the passengers on the ship.”

People are scared this is another COVID-19 situation. How has the global health security situation and outbreak response evolved since 2020?

It is clear that this is not the same situation, as firstly, the hantavirus is a very different virus to and does not transmit as easily as COVID-19. Secondly, based on its response, the WHO has been very clear about communicating the risks to the public about the outbreak, likewise the UK Health Security Agency.

There are of course challenges with an outbreak that is constantly evolving and new information coming in every day which adds uncertainty and can fuel people’s fears, particularly in the current media landscape. It is key that people remain aware of misinformation tactics and try and get information from trustworthy sources like the WHO and UKHSA as these sources are regularly updated with scientifically accurate public health information.

Citizens from 23 countries have been involved in this hantavirus outbreak – what does this tell us about effective pandemic preparedness in a globalised world?

A key factor in the global nature of this outbreak, despite the virus’ relatively poor human-human transmission ability compared to COVID-19, is the international nature of cruise ship travel. In this case, the cruise ship's travelers gathered from all over the world and some disembarked the ship at different points across the globe - all before the outbreak was recognised. This “perfect storm” of global connectivity increased the complexity of public health outbreak containment and contact tracing and helped the outbreak to move somewhat faster than the more typical situation of disease outbreaks that start first as a concentrated local outbreak expanding first via local and eventually via global travel networks (like we saw with COVID-19).

As such, this outbreak reminds us that public health professionals across the world need to keep communicating with each other and the public, not only globally but also on a regional level.

To truly tackle disease outbreaks before they become pandemics, national governments must invest in their own preparedness, not solely rely on ad-hoc donated sources of funding, to ensure sustainability in public health emergency response. Furthermore, involving non-governmental organizations and community actors in pandemic response will ensure that pandemic preparedness is bottom up, sustainable and effective – a model currently being piloted by UK-Public Health Rapid Support Team’s ongoing Guardians of Health joint research project in Brazil and Cabo Verde.

If you are interested in learning more about infectious diseases and how they spread, consider signing up to LSHTM’s short courses; Introduction to Infectious Disease Modelling and Its Applications and Infectious Disease 'Omics.

You can also study LSHTM’s new MRes in Infectious & Tropical Diseases, which is designed to train the next generation of researchers to tackle some of the most pressing health challenges of our time.