Hantavirus: Limited systemic risk in the current context

Executive Summary

Hantavirus is a well-known, long-established virus with several thousand cases reported globally each year. There are two main groups: one in the Americas, causing cardiopulmonary failure (HCPS), which is more severe but rarer, and one in Europe/Asia, causing renal syndrome (HFRS), which is more common but has a lower case fatality rate. Transmission is primarily from rodents to humans; human-to-human transmission is extremely rare and not airborne. There is currently no widely available or effective vaccine.

The virus has limited pandemic potential because of the low transmission rate: human-to-human transmission requires very close contact, typically involving body fluids. In rarer cases, transmission may be linked to living in the same household, sharing a bedroom, or other scenarios involving prolonged close contact. R₀ is generally below 1, meaning that an infected person will cause fewer than one new infection, leading to a natural extinction of outbreaks.

We share the WHO’s view that the risk of a hantavirus pandemic is low but continue to actively monitor the situation.

It is worth noting that while hantavirus itself is not new, our understanding is still evolving. The points in this article reflect current knowledge and may be updated as more information becomes available.

Pathogen and Clinical Features

Hantaviruses are rodent-borne RNA viruses from the family Hantaviridae, causing:

• Hantavirus Cardiopulmonary Syndrome (HCPS) – Americas
• Hemorrhagic Fever with Renal Syndrome (HFRS) – Europe/Asia

The outbreak on the MV Hondius cruise ship in 2026 has been confirmed as a particular type of hantavirus called “Andes virus”, causing HCPS, and is the only one documented to cause human-to-human spread.

Long-term impacts for patients who have recovered have not been observed.

Epidemiology

Worldwide, hantavirus infections occur every year but remain relatively uncommon. The World Health Organization estimates approximately 10,000 to more than 100,000 infections annually, with the greatest burden in Asia and Europe, where HFRS accounts for many thousands of reported cases. In the Americas, infections are far less frequent but can be more severe (HCPS). Overall, events are typically sporadic and localized, most often associated with rural or occupational exposure and specific environmental conditions rather than sustained community transmission.

While all viruses can evolve to become more infectious or more easily transmissible between humans, Hantavirus is under relatively low evolutionary pressure compared to other viruses, meaning the required mutations occur over years rather than weeks.

Transmission and Contagiousness

Hantavirus infection remains primarily environmental and zoonotic (i.e., from animal sources), with transmission occurring through inhalation of aerosolized particles from rodent urine, feces, or saliva, especially in enclosed or contaminated settings.

This supports an “environmental exposure model” for outbreaks, rather than a classical epidemic respiratory model that relies on airborne virus transmission. The Andes virus is the only hantavirus with documented person to person transmission, according to both CDC and WHO.

However, this transmission is rare, requires close, prolonged contact, often in enclosed environments (e.g., shared cabins, intimate exposure), and is typically limited to the symptomatic phase of the infected person. Consequently, most infected individuals do not generate secondary cases. The average number of secondary infections per case (R₀) is typically <1 for hantaviruses, so outbreaks tend to burn out rather than sustain transmission or trigger a pandemic.

Available outbreak analyses from past events suggest transmission occurs in clusters, not continuous chains. Secondary spread is context-dependent (close-contact settings) rather than airborne community spread. Exceptional cluster circumstances, as was the case with the cruise ship, do not indicate baseline transmissibility in the general population.

In the current situation, it is therefore likely that transmission will remain low and limited to close-contact exposures.

Clinical Severity and Case Fatality

The incubation period of hantavirus infection typically ranges from one to six weeks (most often around two to three weeks), with symptom onset usually occurring between four and 42 days after exposure.

HCPS is associated with an estimated mortality rate of between 20% and 40%, with certain outbreaks exhibiting case fatality rates (CFR)¹ of up to 50%.

However, it must be noted that in the rural settings of South America where the virus is endemic, surveillance and reporting are limited, so the actual number of cases is likely to be higher, and the CFR thus lower. Case fatality rates also depend on access to appropriate care (e.g., intensive care services), which can vary substantially across countries and regions.

By contrast, HFRS-associated hantavirus strains circulating in Europe have a lower case fatality rate, typically <1% to 15%.

Comparison with other viruses

These figures are drawn from past outbreaks; R₀ and CFR may vary between events. 

Insurance Risk Assessment

Hantavirus occupies a unique position in the risk matrix: it presents a severity comparable to the Ebola virus, but without any significant transmission dynamics. Unlike COVID-19 or seasonal influenza, there is no risk of systemic accumulation or correlation among insured populations. There is also no evidence of sustained super spreading dynamics comparable to airborne respiratory viruses.

This means hantavirus acts as an exposure-driven, idiosyncratic risk, not a portfolio-wide shock driver. Consequently, it should be modeled as a severe, but isolated zoonotic hazard, with no epidemic scaling potential. Its impact is material at the level of individual claims, but negligible at the portfolio level: there is no correlation risk, and aggregation potential is limited.

Insurers should therefore treat hantavirus as a risk requiring case-specific attention, not as a systemic shock factor. 

Current situation as of May 20th, 2026  

As at the current date, less than 15 cases are confirmed and less than 200 people have been exposed.

Those affected come from more than 20 different countries, all of which are taking measures to monitor the outbreak and isolate suspected cases. 

Footnotes:

¹ The case fatality rate is equal to the number of deaths divided by the number of confirmed cases. For example, with 5 observed deaths, if 100 cases were confirmed the CFR is 5%, but if there are actually 500 cases the CFR is only 1%. 

Sources:

- World Health Organization
- Centers for Disease Control and Prevention