A deadly hantavirus outbreak linked to the expedition cruise ship MV Hondius has drawn worldwide attention after several passengers became seriously ill during a voyage across the South Atlantic Ocean.
At least three people died, while health officials in several countries began tracing passengers and monitoring possible infections.
The outbreak caused concern because the virus involved appears to be the Andes strain of hantavirus, one of the few hantaviruses known to sometimes spread between humans through very close contact. Even so, experts say the virus is far less contagious than illnesses such as COVID-19 or measles.
To help explain the situation, Professor Scott Pegan from the UC Riverside School of Medicine answered questions about hantavirus, how it spreads, and why the current outbreak has attracted so much attention.
Pegan studies emerging infectious diseases and how viruses interact with the human immune system. He also works on antiviral treatments and vaccines for dangerous viruses.
He explained that hantavirus is actually a large family of viruses found in different parts of the world. Some types mainly affect the kidneys, while others damage the lungs and breathing system.
In the Americas, hantaviruses can cause a serious illness called hantavirus pulmonary syndrome, or HPS. This disease can become extremely dangerous because it can rapidly affect breathing and lead to respiratory failure.
According to Pegan, the case fatality rate for severe hantavirus pulmonary syndrome is around 40%. This means that many people who become seriously ill may not survive.
The viruses are mainly carried by rodents such as mice and rats. Most human infections happen after people come into contact with infected rodent urine, droppings, saliva, or contaminated dust.
This often occurs when people clean rodent-infested buildings, barns, cabins, or storage areas. Tiny particles containing the virus can enter the air and be breathed in.
In the United States, most cases involve the Sin Nombre virus, especially in western states. In South America, however, the Andes virus is one of the most important strains.
The recent cruise ship outbreak has raised concern because Andes virus appears more capable of spreading between humans than other hantavirus strains.
Still, Pegan stressed that this type of spread is very different from highly contagious airborne viruses.
He explained that transmission usually requires extremely close contact involving bodily fluids or respiratory droplets. It does not spread easily across large spaces in the air like measles or SARS-CoV-2.
Pegan noted that at the height of the COVID-19 pandemic, one infected person could infect many others very quickly. By comparison, people infected with Andes virus usually infect fewer than one other person on average.
This means the virus spreads much more slowly and less efficiently.
However, confined spaces such as cruise ship cabins can increase the chances of transmission because passengers spend long periods close together, especially family members sharing rooms.
Experts believe this may have played an important role in the MV Hondius outbreak.
The cruise ship began its voyage in Ushuaia, Argentina, and traveled across the Atlantic Ocean with stops at remote islands along the route.
After the outbreak became known, passengers and possible contacts were monitored in several countries including South Africa, Switzerland, Germany, Britain, and the Netherlands.
Health officials stressed that most outbreaks of hantavirus remain small and usually begin with contact between humans and infected rodents.
Pegan said many people wrongly believe hantavirus is only a rural problem. While rural farms and agricultural areas often have more rodents, any place where humans come into contact with infected rodents could potentially become a risk area.
He also warned that public sanitation systems differ widely around the world, which can affect the likelihood of exposure.
Early symptoms of hantavirus infection often resemble the flu. Patients may experience fever, muscle aches, tiredness, headaches, dizziness, nausea, abdominal pain, or diarrhea.
These symptoms can appear between one and eight weeks after exposure.
Several days later, patients with severe disease may suddenly develop coughing and serious breathing problems. In some cases, respiratory failure can happen quickly.
Doctors use blood tests to help confirm hantavirus infection, although testing is usually more accurate after symptoms have been present for at least several days.
Currently, there is no approved vaccine or specific antiviral treatment for New World hantaviruses in the United States. Doctors mainly rely on supportive hospital care such as oxygen support and mechanical ventilation.
Researchers, including Pegan’s team, are working to develop vaccines and treatments for hantaviruses.
The outbreak also highlights the importance of quickly recognizing unusual infectious diseases during international travel. Cruise ships can carry passengers across many countries in a short time, making international cooperation between health agencies especially important.
Pegan said the outbreak should remind both the cruise industry and health officials to take respiratory symptoms seriously and to avoid assuming every illness is simply the flu.
In reviewing the findings, the current evidence suggests that the Andes hantavirus strain is dangerous for infected individuals but far less contagious than many feared. The outbreak also demonstrates how close-contact environments such as cruise ships can create special risks even for viruses that normally spread poorly between humans.
At the same time, experts believe the overall public risk remains low because transmission appears limited and requires very close interaction. The situation also highlights the growing importance of global monitoring for emerging infectious diseases connected to travel and wildlife exposure.
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Source: University of California Riverside.
