It is hardly surprising that, after the COVID-19 pandemic, news about outbreaks of new viral infections causes heightened anxiety. The story of the Andes hantavirus quickly attracted media attention: human-to-human transmission, a cruise ship, an international WHO investigation — all of this inevitably brings to mind the first months of the coronavirus pandemic.
What Is This About?
Hantaviruses are a group of viruses usually carried by rodents. In humans, they can cause two main syndromes: hemorrhagic fever with renal syndrome, more commonly seen in Europe and Asia, and hantavirus pulmonary syndrome (HPS), which is registered mainly in North and South America.
The Andes hantavirus, which caused the current outbreak, belongs to the second group. The virus itself is not new: it has long been known in South American countries, primarily Argentina and Chile. Infection usually occurs through contact with the excretions of infected rodents or contaminated surfaces.
The distinctive feature of the Andes hantavirus is that it is the only hantavirus for which limited human-to-human transmission has been confirmed. This characteristic is precisely what drew the attention of epidemiologists and the media. However, even in such cases, transmission usually requires close and prolonged contact and remains far less efficient than transmission of classic respiratory viruses.
The infection is rare, but it can be severe. Hantavirus pulmonary syndrome initially resembles a common viral infection, with fever, muscle pain, and weakness. However, it can then quickly lead to severe lung involvement and respiratory failure. The fatality rate in individual outbreaks can be high, although cases themselves remain relatively rare.
What Happened?
On May 2, 2026, cases of severe respiratory illness were reported on board the cruise ship MV Hondius. By mid-May, a total of 11 cases had been registered, three of which were fatal. Infection with the Andes virus (ANDV) was laboratory-confirmed in nine patients. Genome sequencing of the virus in patients with confirmed infection showed an almost identical structure. The WHO’s working hypothesis is that the first case — the index patient — was infected on land before boarding the cruise, and that transmission then occurred from person to person in the conditions of the ship.
Why a Cruise Ship Became an Ideal Environment for an Outbreak
Cruise ships have long been considered particularly vulnerable to the spread of infections. The CDC specifically notes that the combination of enclosed spaces, close contact between passengers, shared areas, and prolonged time spent together facilitates the transmission of infectious diseases. This is why outbreaks of viral infections on cruise ships occur regularly
At the same time, it is important to understand that an outbreak on a ship does not in itself mean that the virus spreads easily in everyday life. On the contrary, such situations often become noticeable precisely because they create unusually favorable conditions for transmission.
With the Andes hantavirus, the situation appears similar. Current data indicate that human-to-human transmission is possible, but it usually requires close and prolonged contact. According to the WHO and CDC, the current outbreak was likely the result of a combination of factors, in which a rare virus ended up in unusually favorable conditions for spreading.
Why Experts Do Not Consider This the Beginning of a New Pandemic
Despite the loud headlines, most epidemiologists currently do not view this outbreak as the beginning of a pandemic scenario. The main reason is the low efficiency of human-to-human transmission.
Unlike SARS-CoV-2, the Andes hantavirus does not demonstrate sustained spread within the population. Even in previous outbreaks, transmission was usually limited to close contacts — family members, partners, or people who had spent a long time near the infected person.
In addition, hantavirus infections remain relatively rare even in endemic regions of South America. According to the WHO, 229 cases of HPS were registered in countries of North and South America in 2025.
This does not mean that there is no risk. Hantavirus pulmonary syndrome can be severe and associated with a high fatality rate, and the possibility of human-to-human transmission in this situation requires close monitoring of contacts and the introduction of quarantine measures. However, the likelihood of encountering this infection in everyday life remains significantly lower than with respiratory viruses such as COVID-19.
Conclusion
The story of the Andes hantavirus shows just how much the COVID-19 pandemic has changed our perception of infectious threats. Today, even a limited outbreak of a rare infection instantly becomes global news.
And that is not necessarily a bad thing. Rapid international response, contact tracing, and open discussion of risks are important parts of modern epidemiology. But it is equally important to retain the ability to distinguish a serious outbreak from the beginning of a new pandemic.
For now, the available data point more toward the first scenario, since even in endemic regions of South America, cases of human-to-human transmission remain rare.
Sources
1. World Health Organisation (WHO)
2. U.S. Centers for Disease Control and Prevention (CDC)
3. European Centre for Disease Prevention and Control
4. Reuters
5. University of Minnesota's Center for Infectious Disease Research and Policy (CIDRAP)