The MV Hondius cruise ship, where a hantavirus outbreak began that killed three passengers and infected at least five others, left Cape Verde on May 6. It is due to arrive in Tenerife, in the Spanish Canary Islands, on May 9. From there, the evacuation of passengers, including some Canadians, is expected to begin on May 11.

The strain that caused the outbreak is the Andes virus, the only one in the hantavirus group that is transmissible between humans, notably through saliva droplets and urine.

It is unlikely that the first person infected with this hantavirus contracted it on board the MV Hondius or at a port of call. The incubation period suggests that infection occurred before the ship’s departure from Ushuaia, in southern Argentina, in early April. Several cruise passengers had travelled to Argentina and Chile, where the virus is endemic.

The risk posed by this hantavirus is “low” for “the rest of the world,” the World Health Organization (WHO) stated, which dismisses any similarity with the COVID-19 pandemic.

But what do we know about this hantavirus? We spoke to Professor Benoît Barbeau from the Department of Biological Sciences at the Université du Québec à Montréal. He is an expert in virology whose research focuses on human retroviruses and coronaviruses.

The Conversation Canada: What exactly is the Andean hantavirus?

Dr Benoît Barbeau: It belongs to a group of viruses classified under the genus Orthohantavirus. The Andean strain can occasionally be transmitted to humans by rodents (via particles in their feces or urine) and cause potentially fatal pulmonary syndromes.

What we understand, although we are not yet certain, is that a person may have visited places in Argentina where infected wild mice were present. After coming into contact with particles of feces or urine without realizing it, they may have inhaled these or any other similar material. This is the most likely scenario. This person is thought to have been infected before they boarded the ship. The infection of other passengers continued from there.

It is important to note that the Andean hantavirus is not highly transmissible between humans. Transmission occurs via urine, saliva or repeated contact, for example, on a ship, in the same cabin, with frequent contact. The virus is not transmitted via aerosols, like the flu or COVID. That is reassuring, at least.

TCC: It is not that easily transmitted, but it is far more deadly…

B.B.: Indeed. Hantaviruses cause two types of illness: a hemorrhagic fever, similar to that caused by Ebola, which has a high mortality rate (Editor’s note: up to 40 per cent), or a pulmonary syndrome, which is just as lethal. At present, there are no antiviral treatments. We can only alleviate the symptoms.

TCC: This virus is less effective at spreading, but its incubation period can be long…

B.B: Indeed, the incubation period can be up to eight weeks, compared to two to three days for COVID. This obviously complicates the chain of transmission. That said, the person will not be contagious during those eight weeks, but most likely will become more so when symptoms appear or just before.

TCC: Why is South America more affected by this form of hantavirus?

B.B.: We’re not entirely sure. In fact, generally speaking, we know very little about the virus, which was only identified in the late 1970s. So it is a relatively recent virus for us, even though we know that, throughout history, certain outbreaks may have been linked to it. It is present in several places (including Canada), but remains very rare. Since 1989, around 100 cases have been recorded in humans in Canada. Of these, about 20 have died. That said, other people may have been infected but the cases weren’t recorded.

What we do know is that the deer mouse is the main source of infection. It can carry the virus but is more resistant to the infection, so it does not become ill, which makes the risk of transmission higher. It acts as a reservoir, much like the bat does for several viruses, such as Ebola, coronaviruses and the rabies virus.

TCC: Will this current, highly publicized outbreak spur further research?

B.B.: Possibly… we hope it will prompt governments to pay attention to it. It would be in our interest to investigate further. But more funding is directed towards research into viruses that have the greatest impact on a country and its population. And since the majority of hantaviruses are not transmissible from human to human, there is not much incentive for governments to invest in research.

Putting energy and money into developing a vaccine might not be the best approach for that matter, since a vaccine effective against the Andean type, for example, would very likely be ineffective against other hantaviruses, and there are many of them. That adds to the complexity. It’s better to invest in treatments; that’s more effective. We could start by repurposing or testing other known antivirals.

TCC: What can we expect next?

B.B.: It all depends on the findings of the epidemiological investigations. Some passengers left the cruise ship before it was known there was an outbreak. We need to trace them, and the people they have been in contact with. The transfer of passengers still on board the ship is due to take place in the coming days from the Canary Islands. People will then be repatriated to their respective countries. They will be isolated and confined under measures that will certainly be strict, so there is no risk of transmission within the general population.

I believe we can be confident. But we must remain very vigilant.

Benoit Barbeau ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.