Many of us had never even heard of it before. Yet a single news story was enough to trigger widespread social alarm. After 2020, that reaction is understandable. However, this is neither a new virus nor an exceptional one. Hantavirus is a silent presence that medicine has known about for decades, but it re-emerges whenever the balance between the environment, animals, and humans changes: not a sudden explosion, but a cyclical return linked to fluctuations in rodent populations and ecological conditions that regulate its spread.
Origins and history of the virus
Professor Ilaria Vicenti, Professor of Microbiology and Clinical Microbiology at UniCamillus University, explains that hantaviruses are a group of viruses that mainly circulate among wild rodents, which represent their primary reservoir. They recently returned to media attention because of an outbreak aboard the cruise ship MV Hondius in May 2026, which caused three deaths and eleven confirmed cases.
Their presence, however, has long been known. One of the earliest possible traces of disease associated with these viruses dates back to London in the 1500s, while the virus itself was first identified in South Korea in the 1970s near the Hantan River, from which it takes its name. Later, in the 1990s, outbreaks were also observed in South America, where a particular strain called Andes appeared; in rare cases it can also spread from person to person.
It was precisely the Andes strain that was identified as the cause of the recent cruise ship event, once again attracting the attention of the scientific community and international media.
Geographical distribution and real risk
The geographical distribution is uneven and helps define the actual epidemiological risk. In Europe and Asia, Old World strains such as Hantaan and Puumala circulate and may cause a fever-like illness involving the kidneys. In these cases, mortality is generally low, often below 1% in the most common European strains.
In the Americas, however, New World strains such as Sin Nombre and Andes circulate and can cause a more severe form involving mainly the lungs and heart, with mortality reaching 30–50% in the most serious cases.
Professor Vicenti reassures that in Italy and Europe the risk for the population remains low and is mainly linked to contact with environments contaminated by infected rodents.
Transmission
Transmission to humans occurs almost always indirectly through the environment. Infection mainly occurs by inhaling tiny particles contaminated with urine, feces, or saliva from infected rodents. Each type of hantavirus is generally associated with a single rodent species acting as its natural reservoir.
In the vast majority of cases, the virus is not transmitted from person to person. Human-to-human transmission is extremely rare and concerns only specific situations related to the Andes strain, in contexts of very close and prolonged contact.
Why it does not become a pandemic
To understand why hantavirus, despite being capable of causing very serious disease, has never generated a global pandemic, comparison with COVID-19 is inevitable. The main difference lies not so much in the severity of the individual case as in the virus’s ability to spread easily from one person to another.
SARS‑CoV‑2 spread very easily between individuals: on average, one infected person could infect two or three others during the initial phases of the pandemic, enabling rapid global spread. Hantaviruses, on the other hand, are rarely transmitted between people and in most cases not at all, because transmission occurs mainly from animals to humans.
Even in the rare outbreaks linked to the Andes strain, spread does not persist over time or expand on a large scale thanks to isolation measures and contact tracing.
Symptoms and diagnostic difficulties
One aspect that makes hantavirus difficult to recognize is that, at least in the early stages, symptoms can easily be mistaken for those of a common viral infection. The most common symptoms are fever, severe fatigue, muscle pain, headache, and gastrointestinal disorders. Initially, it may therefore resemble a simple flu.
In forms where person-to-person transmission has been observed, the period between infection and symptom onset is generally 2–4 weeks, but in some cases it can reach around 40 days.
Diagnosis and clinical management
Early diagnosis is essential mainly for case management and public health rather than for targeted therapy. Diagnosis is based on laboratory tests that directly detect the virus or the immune system’s response. Viral genetic material or the first antibodies produced by the body can be identified through a simple blood sample.
Unfortunately, there are no specific treatments or approved vaccines. Treatment is therefore supportive and aims to help the patient while the body fights the infection. In milder cases oxygen therapy may be sufficient, while more severe cases may require assisted ventilation or support of vital functions.
Some antiviral drugs, such as Ribavirin and Favipiravir, are still being studied, but their effectiveness has not yet been definitively confirmed.
Prevention and environmental control
Prevention remains the central pillar and is based on behavioral and environmental measures. For viruses transmitted only by rodents, the most effective measures concern rodent control in general, while at the individual level it is important to avoid contact with droppings in enclosed environments.
The World Health Organization also recommends avoiding raising dust when cleaning potentially contaminated spaces. Instead, surfaces should first be moistened and then disinfected. The virus is sensitive to disinfectants because it is surrounded by a lipid envelope that is easily damaged by substances such as hypochlorite, found for example in bleach.
In the rare cases in which person-to-person transmission of the Andes strain has been observed, health authorities such as the CDC and ECDC recommend surveillance or quarantine of close contacts for up to around 40 days, together with the use of protective equipment for healthcare workers.
Risk perception and communication
Risk communication is also important and often does not coincide with the real epidemiological situation. To avoid alarmism, it is essential to contextualize the numbers, explain the actual transmission mechanisms, and communicate transparently what is known and what is still under study.
The most common mistake is automatically associating the appearance of a new virus with the immediate risk of a pandemic. In reality, for a virus to spread globally, several biological characteristics must coexist: high transmissibility between people, the ability to spread before symptoms appear, efficient adaptation to humans, and lack of immunity in the population.
The role of climate change
Environmental changes can also play an indirect role. Climate change and ecosystem alterations may influence the circulation of hantaviruses: milder winters or periods of heavy rainfall can favor increases in rodent populations, which are the virus’s main reservoir. This increases the likelihood of contact between humans and animals and therefore the risk of infection.
A historical example is the 1993 epidemic in the Four Corners region of the United States, linked precisely to an abnormal increase in rodent populations.
In the case of hantavirus, however, these conditions do not combine in a way that supports sustained person-to-person spread. For this reason, it remains a typical example of an infection transmitted from animals to humans: an ancient virus, always present, which re-emerges not because it is new, but because the conditions that make it visible have changed.