Hantavirus explained: how does it spread and who is most at risk?

Summary

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Science Weekly: Hantavirus Explained – How Does It Spread and Who Is Most at Risk?

The Guardian | May 5, 2026
Host: Madeline Findlay
Guest: Professor Jonathan Ball (Deputy Vice Chancellor of Tropical Disease Biology, Liverpool School of Tropical Medicine)

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Episode Overview

This episode of Science Weekly responds to recent news of a suspected hantavirus outbreak aboard the cruise ship MV Hondias off the coast of West Africa. With global attention on this rare but deadly virus, host Madeline Findlay investigates what hantavirus is, how it spreads, who is at risk, and what might have led to this unusual cruise ship outbreak. Expert virologist Professor Jonathan Ball explains the science behind hantavirus transmission, discusses outbreak risks and control, and offers practical guidance for public health.

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Key Discussion Points & Insights

What is Hantavirus? (02:35)

• Professor Ball describes hantavirus as a virus that circulates widely in rodents, with many different species across the world (excluding Antarctica).
• There are two main groups:
  • New World Hantaviruses (primarily in the Americas) – cause "hantavirus pulmonary syndrome," a severe respiratory illness.
  • Old World Hantaviruses (Africa, Asia, Europe) – can cause "haemorrhagic fever with renal problems."

“We can divide the hantaviruses into two main groups... The New World hantaviruses can cause what we call hantavirus pulmonary syndrome, which is quite a severe respiratory problem... The Old World ones can cause haemorrhagic fever with renal problems.”
— Prof. Jonathan Ball [02:35]

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How Do Humans Become Infected? (03:33)

• Main transmission to humans is through inhalation of airborne particles from dried rodent urine or feces.
• Higher risk for people frequently exposed to rodents (occupation, environment).

“Humans become infected when they become exposed predominantly to rodent urine or faeces... Particularly as it dries, it can form little particles that can become airborne.”
— Prof. Jonathan Ball [03:39]

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Human-to-Human Transmission: How Rare? (04:08)

• Transmission between humans is rare but possible in close contact situations (family, healthcare workers).
• Some evidence exists for sexual transmission.

“Human to human transmission is rare, but there is some evidence of transmission amongst people who are in very close proximity... and there’s also evidence of sexual transmission.”
— Prof. Jonathan Ball [04:17]

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Mortality Rates and Severity (04:41)

• Most cases are asymptomatic or mild; many go unreported.
• Serious illness occurs in a minority, with mortality ranging from 5–15% among those who become gravely ill.

“Most infections are probably either asymptomatic or mild... very, very few of those infections will result in serious disease. But if people do become unwell... some individuals will die – between 5 and 15%, for example.”
— Prof. Jonathan Ball [04:50]

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Why is the Cruise Ship Outbreak Unusual? (05:35)

• Outbreaks are generally well contained and do not involve large numbers.
• The unique risk here is the "captive, contained bunch of people" on a cruise ship, increasing the chance of human-to-human spread if it occurs.

“What’s unusual here is you’re talking about what are essentially a captive contained bunch of people... if there is human to human transmission, then they’re at greater risk because they are incarcerated on this cruise ship.”
— Prof. Jonathan Ball [06:00]

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How Did the Outbreak Likely Start? (06:34)

• Hypothesis: The Andes virus (common in Argentina) may be responsible.
• Exposure could have occurred before boarding or during island stops.
• Rodent stowaways are a plausible source; rodents are globally widespread and ship transport is common.

“The hypothesis of rodents stowing away on the ship is certainly plausible... It’s very difficult to keep rodents off ships.”
— Prof. Jonathan Ball [07:03]

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Containment & Prevention On Board (08:50)

• Actions likely include minimizing passenger mixing, deep cleaning, and close health monitoring/isolation.

“You will try and minimise the amount that people are mixing. But also... there’d be a process of deep cleaning the ship... And I think the most important thing is... to be vigilant in monitoring the health of the passengers…”
— Prof. Jonathan Ball [09:00]

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Incubation Period and Future Cases (09:37)

• Incubation can be up to several weeks, so more cases may still emerge.
• Essential for passengers to be allowed to disembark and receive proper care.

“The incubation period for the hantavirus can be up to several weeks... I think it’s really important that the ship is allowed to dock somewhere and... those who are infected to get the care and treatment that they require.”
— Prof. Jonathan Ball [09:47]

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Treatment Options (11:08)

• No licensed, specific treatments. Ribavirin, a broad antiviral, can be used compassionately with some reported benefits.
• Severe cases are managed supportively (oxygen, intubation, mechanical ventilation).

“There are no specific treatments for hantavirus infection that have been licensed, but there are treatments that can be used on a compassionate basis... One such treatment is called ribavirin...”
— Prof. Jonathan Ball [11:13]

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Protecting Yourself (12:10)

• Avoiding exposure to rodents and their excretions is key; those with frequent exposure (including pet rat keepers) have higher risk.
• Cruise ships pose a risk because of close living quarters but are not singled out for avoidance.

“The main thing is to avoid or limit your exposure to rodents and the excretia. We know that people who have a lot of exposure to rats... means you’ve got an increased risk of exposure to the virus.”
— Prof. Jonathan Ball [12:23]

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Next Steps for the Cruise Ship & Passengers (13:24)

• Ongoing monitoring, testing, and isolation where required.
• Authorities must balance public health safety with humane treatment (preventing rodent escape, monitoring passengers).
• Likely docking in the Canary Islands (Tenerife).

“I heard that it’s likely that the ship will be allowed to go onto the Canary Islands, where it hopefully will dock, possibly at Tenerife. And I’m sure then the passengers will be disembarked and isolated if need be.”
— Prof. Jonathan Ball [13:40]

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Memorable Quotes

• On transmission: “It’s very good at stowing away on ships and being transported as humans go about their daily business.” — Prof. Jonathan Ball [07:35]
• On cruise ship risk: “I would really like to go on a cruise ship...the problem is because you are living cheek by jowl with other people... if you get an infectious agent introduced... it does help the spread.” — Prof. Jonathan Ball [12:23]

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Timestamps for Major Segments

• [02:35] What is hantavirus?
• [03:33] Human infection and transmission
• [04:17] Human-to-human transmission and severity
• [06:00] Why the cruise ship outbreak is unusual
• [07:03] How the outbreak may have started
• [09:00] Containment and precautions on board
• [09:47] Incubation period and handling the outbreak
• [11:13] Treatment options explained
• [12:23] Advice on protection and cruise ship risk
• [13:40] Public health response and what's next

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Conclusion

This episode provides an in-depth, clear-eyed look at the rare but serious threat posed by hantavirus, using the context of the recent cruise ship outbreak to explore its biology, risks, and prevention. Professor Jonathan Ball delivers critical information and practical context, making the science accessible and relevant. For further coverage, visit The Guardian’s ongoing reporting on the outbreak.

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Transcript

[Andrew]

This is the guardian.

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[Sarah Elk]

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[Madeline Findlay]

Over the weekend, reports emerged of a suspected hantavirus outbreak on a luxury cruise ship. Two cases of hantavirus have been formally confirmed after three people died in a suspected outbreak while on a cruise ship off the coast of West Africa traveling from Argentina to the Cape Verde Islands. Another four suspected cases were then identified on the MV Hondias. The World Health Organization has now stated it believes there may be some human to human transmission among very close contacts and medical personnel have boarded the ship. Human infections are rare, but the virus was also thought to be behind the death of actor Jean Hackman's wife Betsy Arakawa last year.

[Sarah Elk]

The medical investigator saying an autopsy shows 65 year old Arakawa died of hantavirus.

[Madeline Findlay]

So what is hantavirus, how is it transmitted and how dangerous is it? From the Guardian I'm Madeline Findlay and this is Science Weekly. Professor Jonathan Ball, your Deputy Vice Chancellor of Tropical Disease Biology at Liverpool School of Tropical Medicine. First of all, what is hantavirus?

[Professor Jonathan Ball]

Okay, so hantavirus is a virus that circulates widely in rodents. There are different species of hantavirus across all continents except Antarctica, although there may well be some rodents living there that could possibly harbour hantavirus. I'm not sure we've extensively checked, but essentially we can divide the hantaviruses into two main groups, the New World hantaviruses, which mainly are found in the Americas, for example, and the Old World hantaviruses, which are in places like Africa, Asia, and also Europe, the New World Hantaviruses can cause what we call hantavirus pulmonary syndrome, which is quite a severe respiratory problem. It can really interfere with your ability to breathe correctly, whereas the Old World ones can cause haemorrhagic fever with renal problems as well.

[Madeline Findlay]

And so these are viruses normally found in rodents. How do humans tend to become infected?

[Professor Jonathan Ball]

Humans become infected when they become exposed predominantly to rodent urine or faeces. Basically the rodent excretia, and particularly as it dries, it can form little particles that can become airborne. And then people acquire the virus when they breathe in these contaminated particles. And anybody who is exposed to rodents regularly is at increased risk of getting a hansavirus infection.

[Madeline Findlay]

And the WHO is now saying that human to human transmission on the cruise ship is likely. How rare is that?

[Professor Jonathan Ball]

So human to human transmission is rare, but there is some evidence of transmission amongst people who are in very close proximity, so family members, for example. And we certainly know that there is a risk of transmission for healthcare workers, and it can occur through either contact with contaminated materials that the person is producing. But I think there's also evidence of sexual transmission.

[Madeline Findlay]

And you said infections can be very severe. What are the kind of mortality rates that we're looking at for each of the different lineages?

[Professor Jonathan Ball]

Well, it's almost difficult to come up with a definitive answer on that, and I'm not hedging my bets. The reason I say that is that most infections are probably either asymptomatic or mild. So we think there's between 100,000 and 200,000 cases of hantavirus infection around the world. But that's probably the tip of the iceberg. And very, very few of those infections will result in serious disease. But if people do become unwell, then their risk of death is increased. Some of the individuals will die between 5 and 15%, for example.

[Madeline Findlay]

Okay, so because some people do present as asymptomatic or mild, there will be plenty of cases that aren't being picked up. And of course, there is additional risk if you're working with or near rodents or happen to live in a place where there might be rodents nearby. But how unusual is the suspected outbreak that we're seeing on the cruise ship on MV Hondias?

[Professor Jonathan Ball]

I think it's fair to say that outbreaks generally are relatively well contained, and we don't get huge reports of significant outbreaks. What's unusual here is you're talking about what are essentially a captive contained bunch of people. It means that if there is human to human transmission, then they're at greater risk because they are incarcerated on this cruise ship. If you think about most outbreaks, it's usually in populations who aren't constrained to a single place and co living with one another.

[Madeline Findlay]

And when it comes to how this outbreak started, I know there have been questions raised around the fact that the cruise ship was stopping off on islands that have bird populations and therefore are likely to have big rodent populations, or that the virus was maybe brought aboard by somebody who was already infected. The WHO now say that they've been told that no rats were found aboard the ship. But when something like this happens, what are some of the explanations that experts would look at and consider?

[Professor Jonathan Ball]

I think the WHO are working on the hypothesis that it's probably the Andes virus, which is quite prevalent in South America and in particular in Argentina. And so, you know, both of those scenarios, either people picking up the virus before they boarded the ship in Argentina, or on the stop offs en route, the likelihood of people being exposed is certainly true. We know that rodents are one of the most prevalent groups of animals worldwide. And wherever you got large rodent populations, there's a chance of becoming exposed. I think one of the things that's very noticeable about hantavirus infections, and we used to see this a lot in Europe, is often virus cases or outbreaks would mirror good years for things like beech tree nuts. So these periods of great production of seeds, and essentially because there's so much food, the rodent populations explode and therefore the hantavirus prevalence in those animals increases. I mean, that's just as an aside, but I think the hypothesis of rodents stowing away on the ship is certainly plausible. It's very difficult to keep rodents off ships. If we think about one hantavirus called the sole hantavirus, it's pretty much worldwide distributed and that's because it infects the common rat, so Ratis norvegicus. And we know that the common rat is found in every continent. It's very good at stowing away on ships and being transported as humans go about their daily business. So I think one of the questions that the authorities that the scientists will be trying to work out is how did this outbreak occur so that similar ones can be prevented in future?

[Madeline Findlay]

And on the subject of prevention, I wonder what kind of precautions are they likely to be taken on board now to reduce the likelihood of further infection?

[Professor Jonathan Ball]

You will try and minimise the amount that people are mixing. But also, and I'm sure this has already happened, there'd be a process of Deep cleaning the ship, so trying to make sure that there aren't areas where there is contamination. So it's all about cleanliness and then isolation. And I think the most important thing is, is to be vigilant in monitoring the health of the passengers to ensure that if anybody does start to show symptoms that could be hantavirus infection, that those individuals are isolated from the rest of the ship's passenger and crew as quickly as possible.

[Madeline Findlay]

Presumably because of the long incubation time, the people involved in dealing with this outbreak are probably expecting that there are going to be more cases coming.

[Professor Jonathan Ball]

Yeah, there may well be more cases. We know that the incubation period for the hantavirus can be up to several weeks. And so that gives the virus a long window during which it can replicate but also potentially transmit. So I think it's really important that the ship is allowed to dock somewhere and for the people on board to be allowed off the vessel to be tested and those who are infected to get the care and treatment that they require.

[Madeline Findlay]

Coming up, how is hantavirus treated and what will health authorities do now?

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[Madeline Findlay]

Jonathan, are there any treatments available for those who have been infected?

[Professor Jonathan Ball]

There are no specific treatments for hantavirus infection that have been licensed, but there are treatments that can be used on a compassionate basis. And there's some evidence that they may help relieve some of the symptoms and help prevent serious symptoms from developing. And one such treatment is called ribavirin, which is a fairly broad acting antiviral. So it directly inhibits the replication the growth of the virus. But as I say, if it is the Andes virus or a New World hantavirus and the normal symptoms or serious symptoms develop, these viruses we know cause difficulty with breathing, then it's the normal things that we do for patients who are struggling for breath, and that would be to give them additional oxygen. And if that doesn't work, they may what you call, intubate the patient. So that means putting a pipe inside their airway to try and help with that breathing. And they can be mechanically ventilated if the worst plays out.

[Madeline Findlay]

And Jonathan, although this is present all around the world, this disease is very, very rare. But is there anything we should bear in mind when it comes to protecting ourselves, aside from avoiding cruise ships?

[Professor Jonathan Ball]

Yes. I wouldn't like to comment on cruise ships, whether or not we should go on them. My personal opinion is I would really like to go on a cruise ship. You know, we do see a lot of outbreaks of different viral infections in cruise ships. And a lot of the problem is because you are living cheek by jowl with other people. And so if you get an infectious agent introduced into that population, it does help the spread. And we all know that there are lots of norovirus outbreaks on cruise ships, for example, and we can all think back to Covid and the cruise ship that got stranded because it had a Covid outbreak. So other than avoiding cruise ships, which I wouldn't advocate and I wouldn't not advocate, the main thing is to avoid or limit your exposure to rodents and the excretia. We know that people who have a lot of exposure to rats through their work or because they keep pet rats, for example, means that you've got an increased risk of exposure to the virus.

[Madeline Findlay]

And just finally, Jonathan, you mentioned about getting the passengers off the cruise ship and monitoring and surveillance. Is that what happens next in terms of this outbreak? Is it just keeping an eye on all of the passengers to make sure that they're not showing any symptoms?

[Professor Jonathan Ball]

Yeah, clearly, authorities, wherever they dock, they need to be reassured that there's no risk of either the virus being imported into the place that they dock or if there are rodents present on the ship, that those rodents don't get out onto the land. But the reality is there are ways that we can limit the risk of rodents if they are on the ship from escaping, but also equally get patients and passengers off the ship and then tested and if necessary, monitored. So I think that will be happening next. I heard that it's likely that the ship will be allowed to go onto the Canary Islands, where it hopefully will dock, possibly at Tenerife. And I'm sure then the passengers will be disembarked and isolated if need be.

[Madeline Findlay]

Well, Jonathan, thank you very much for joining us today.

[Professor Jonathan Ball]

No problem at all.

[Madeline Findlay]

Thanks again to Professor Jonathan Ball. You can find our coverage of the hantavirus outbreak on theguardian.com and that's it for today. This episode was produced by me, Madeline Finlay, and the executive producer is Ellie Burey. We'll be back on Thursday. See you then.

[Andrew]

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