What is hantavirus?
Hantaviruses, scientifically known as orthohantaviruses, are a group of viruses that predominantly reside in rodents but can also infect humans. According to Professor Adam Taylor from Lancaster University, the world recognizes at least 38 species of hantavirus, with 24 known to cause illness in humans. Mice, rats, and voles serve as the primary carriers for these viruses.
Dr. Yomani Sarathkumara, a postdoctoral research fellow at the University of Queensland, notes that hantavirus infections in humans are “extremely rare” and often misidentified as other conditions in tropical regions, such as leptospirosis, another disease transmitted by animals.
How is the virus spread and what are the symptoms of hantavirus?
Humans can contract hantaviruses through inhalation or direct contact with infected rodent droppings, urine, and saliva, though transmission through bites and scratches from infected animals is less common.
“Communities involved in agriculture worldwide are at a greater risk,” Sarathkumara explains, due to their increased chances of encountering infected rodents.
Associate Professor Vinod Balasubramaniam, a molecular virologist at Monash University Malaysia, emphasizes that hantaviruses are typically linked to environmental exposure involving rodents and do not usually transmit easily between people, unlike viruses such as the flu or COVID-19.
Hantaviruses are categorized into two main lineages: the old world hantaviruses and the new world hantaviruses.
Old world hantaviruses are found in Europe and Asia – these include puumala hantavirus, Hantaan virus, and Seoul virus. In humans, they typically cause haemorrhagic fever with renal syndrome (HFRS), which affects the kidneys. Symptoms can include intense headaches, back and abdominal pain and fever, and potential kidney damage.
New world hantaviruses are found in the Americas, and usually cause hantavirus pulmonary syndrome. The most common type in South America is the Andes virus, which is primarily spread by the long-tailed pygmy rice rat.
“New world hantaviruses cause really rapidly progressive pulmonary syndrome and respiratory failure,” Balasubramaniam said. Early on, an infection may cause flu-like symptoms such as fever, fatigue and muscle aches, which makes “early diagnosis really difficult”, he said.
In March 2025, Betsy Arakawa, the wife of actor Gene Hackman, was found to have died in their Santa Fe home from hantavirus pulmonary syndrome, prior to the death of her husband, who had Alzheimer’s, in the absence of her care.
Hantaviruses can have long incubation periods – between one and eight weeks long, Balasubramaniam said.
According to Taylor: “A small number of studies have documented human-to-human spread of the Andes strain in South America, but a systematic review of the research didn’t find enough evidence of human-to-human transmission.”
How did the hantavirus outbreak on the cruise ship occur?
The WHO said an investigation into the suspected hantavirus outbreak on MV Hondius was under way. Though we don’t yet know exactly how it occurred, Balasubramaniam said: “There are a couple of biologically plausible possibilities.”
The first is the possibility of rodent contamination in the vessel itself – “if infected rodents had access to storage areas … cabins and other enclosed spaces”.
The second is – because of the long incubation periods of hantaviruses – that the outbreak “might not have necessarily originated from the ship itself”, Balasubramaniam said. “Passengers or crew members could theoretically be exposed during land-based activities.”
The third – but least likely – is person-to-person transmission. “This is plausible theoretically but it’s highly [unlikely],” Balasubramaniam said.
“The main risk is disturbing contaminated rodent materials … in close or poorly ventilated spaces,” he said. “The risk is not usually from just sharing [the] same space of air with an infected person.”
What is the mortality rate for hantavirus? Is there a treatment?
Fatality rates from HFRS, caused by the old world hantaviruses, are estimated to be between 1% and 15%.
“New world hantaviruses … cause much more severe symptoms and the chances of mortality are much, much higher,” Balasubramaniam said. Hantavirus pulmonary syndrome has a fatality rate of about 40% in the Americas.
“We don’t have a definitive antiviral [drug] that works really well,” Balasubramaniam said. Infections were typically treated with supportive management, which made early diagnosis important, he added. However, broad-spectrum antivirals are being researched for use as an early treatment.
For hantavirus pulmonary syndrome, supportive care includes oxygen, fluid management, blood pressure support and ventilation.
