Hantavirus: The Virus Behind an Unusual Outbreak
- tiqbal28
- 14 minutes ago
- 4 min read
By David Dreifuss
On 2 May 2026, the World Health Organisation was notified of a cluster of severe respiratory illnesses on the MV Hondius, a Dutch-flagged expedition cruise ship travelling from Ushuaia, Argentina, across the South Atlantic. By 20 May 2026, the European Centre for Disease Prevention and Control (ECDC) reported 11 cases linked to the ship, including 9 confirmed cases, 2 probable cases, and 3 deaths. The virus had by then been identified as Andes hantavirus, the passengers evacuated and quarantined in their respective countries, and the ship was docked in Rotterdam for sanitation. That combination of a relatively rare but deadly virus, a cruise ship, and passengers scattered for quarantine across many countries made the event unusual. But the virus family has been known to scientists for a long time.
The “without name” virus
The name “hantavirus” goes back to the Hantaan River area of Korea. During the Korean War, about 3,200 cases of what is now called haemorrhagic fever with renal syndrome were reported among United Nations forces in Korea. The illness was severe and dominated by fever, vascular leakage, shock, and kidney injury. The agent causing the disease was not definitively known until 1978, when scientists isolated the virus from the striped field mouse, Apodemus agrarius. The prototype virus was then named Hantaan virus after the river. However, after local communities protested naming the virus after the location, the virus became known as Sin Nombre virus (the “without name” virus), and the disease was named hantavirus pulmonary syndrome, or HPS.
For decades, that was the classic hantavirus story: rodents, rural exposure, and a disease that often affects the kidneys. Then, in 1993, a very different clinical picture appeared in the Four Corners region (the intersection of Arizona, New Mexico, Colorado, and Utah) of the United States. The 1993 outbreak cluster—unlike previous cases—presented a very high fatality rate, making the syndrome new enough that investigators initially did not know what they were looking at.
The United States Centres for Disease Control and Prevention (CDC) and collaborators identified a novel hantavirus in patient tissue and in deer mice, Peromyscus maniculatus, trapped near patients’ homes, confirming the zoonotic origin of the disease.
A peculiar type of Hantavirus
Andes virus, the virus identified as having caused the 2026 MV Hondius outbreak, belongs to that same New World group of hantaviruses. It circulates in parts of southern South America, especially Argentina and Chile, and can cause that characteristic pulmonary syndrome. The usual route is still zoonotic: inhaling material contaminated by infected rodent urine, droppings, or saliva.
But the Andes virus itself is unusual because it is the only hantavirus for which person-to-person spread is well documented, although that spread is less common and usually limited to close contact with someone who is ill.
This picture became clear in southern Argentina in 1996, during an outbreak of 20 cases around El Bolson, Bariloche, and Esquel. The biggest outbreak came two decades later, in Epuyen in 2018-2019: one likely rodent-to-human jump led to a chain of infections driven mostly by three symptomatic people at social events or in close contact with others, resulting in 34 confirmed infections and 11 deaths before isolation and contact quarantine brought it under control.
That history is why the recent MV Hondius outbreak is being handled carefully despite the estimated low risk to the wider public. Thanks to rapid sequencing work and collaboration between public health and research teams, genomic data already allows us to understand some key aspects of the outbreak. The Hondius viruses are related to other known South American Andes viruses, with no evidence at that point of new features that would make the virus more transmissible or more severe. Sequences from the available cruise-ship cases were also extremely closely related to one another, often even identical, which is an important piece of evidence for onboard human-to-human transmission.
Early detection is critical
The latest hantavirus outbreak is a reminder that hantaviruses deserve careful surveillance. It is also a clear example of why early detection of possible human-to-human transmission matters.
In the WaSPP project, we are developing wastewater surveillance approaches to support the early detection of spillover infections and outbreaks, including hantaviruses. As part of this work, we have developed methods to recover hantavirus from wastewater samples for subsequent detection and genetic sequencing using nanopore technology.
Dr Joyce Odeke Akello, Research Fellow and WaSPP Sample Concentration & Extraction Co-lead, shares:
“We designed and tested different primer sets (short pieces of genetic material that act like a “search tool” to find specific parts of the virus) using hantavirus G-block fragments, which are safe synthetic pieces of viral genetic material that mimic the virus in the laboratory. After evaluating different testing conditions, we successfully developed a working assay for hantavirus detection in wastewater samples.”
The assay is now planned for field validation with partner institutes within the WaSPP consortium to assess its performance in real-world settings. “We aim to detect signs of human-to-human transmission and possible viral adaptation before they become obvious through clinical surveillance alone, which would give more time to react," says Dr Joyce Odeke Akello.
Our work with WaSPP highlights the growing importance of wastewater surveillance for monitoring zoonotic viruses such as hantavirus, supporting early detection, outbreak preparedness, and public health response.
About the Author
David Dreifuss is a Research Associate at Imperial College London
Comments