Hantavirus: a primer

Recent media coverage of a hantavirus outbreak linked to an expedition cruise ship in May 2026 has brought a relatively uncommon zoonotic infection into public discourse. While the overall risk to the public remains low, the event is a useful reminder of how environmental exposures, global mobility, and occasionally unusual transmission dynamics can intersect to create complex IPC challenges. This blog provides a practical primer for healthcare professionals, with a focus on what matters most for IPC.

What is hantavirus?

Hantaviruses are rodent-borne viruses, typically transmitted to humans through inhalation of aerosolised particles from rodent urine, droppings, or saliva. They are globally distributed and cause two main clinical syndromes: hantavirus pulmonary syndrome (HPS), characterised by rapid respiratory deterioration, and haemorrhagic fever with renal syndrome (HFRS), which is more often seen in Europe and Asia and involves renal impairment. Although rare, hantavirus infections can be severe, and in some settings the case fatality rate is high.

Epidemiology: transmissibility, severity, and incubation

For most hantaviruses, transmissibility is low because infection is almost entirely driven by environmental exposure rather than onward human transmission. In practical IPC terms, this means that most cases represent a “dead-end” infection from a transmission perspective. However, Andes hantavirus (ANDV) behaves differently and understanding its transmission characteristics is key.

Data from a well-described outbreak in Argentina show that ANDV can achieve sustained person-to-person transmission under certain conditions. In this outbreak, before isolation and quarantine interventions were introduced, the median R (i.e. the R0) was approximately 2, falling to 0.96 once control measures were implemented.

This sets ANDV apart from other hantaviruses in that it seems to have the capability to spread through close contact, particularly in settings with intense social mixing (such as on a cruise ship, for example...!). The same outbreak demonstrated the importance of “super-spreading” dynamics, with just three individuals responsible for the majority of secondary cases.

In terms of severity, the case fatality rate associated with hantavirus disease can approach 50% - but this will depend on clinical presentation, and supportive care given. For HPS overall, case fatality rates are often reported in the range of 25–40%, reflecting the severity of cardiopulmonary involvement and the rapid clinical deterioration that can occur. In infections causing HRFS, which are more commonly seen in Europe and Asia, case fatality rates are typically lower and can range from <1% to around 10–15%, depending on the specific virus.

One of the challenges in terms of managing potential hantavirus exposure is the extended incubation period. Across hantaviruses as a group, the time from exposure to symptom onset typically ranges from around 1 to 8 weeks, although most cases present within 2–4 weeks.

Given the potential for human-to-human spread, the high case fatality rate, lack of vaccination or specific antiviral treatment mean that ANDV is classified as an airborne high consequence infectious disease (HCID) in the UK.

What does the NEJM outbreak study tell us?

An important study published in the New England Journal of Medicine in 2020 provides a detailed analysis of Andes hantavirus transmission. The study investigated an outbreak in Argentina in 2018–2019 involving 34 confirmed cases and 11 deaths. The outbreak began with a single spillover event from a rodent reservoir into humans, but subsequent spread was driven by person-to-person transmission. This transmission was amplified by a small number of individuals who attended crowded social events while symptomatic, effectively acting as “super-spreaders”.

In the study, transmission chains were reconstructed across multiple generations, with evidence that infection often occurred through close contact during the early symptomatic phase, sometimes as early as the first day of fever. The estimated incubation period ranged from 9 to 40 days, and the serial interval averaged around 23 days.

Importantly for IPC, once public health measures were introduced, including isolation of cases and quarantine of contacts, transmission declined significantly, with the reproductive number falling below 1. This provides strong real-world evidence that relatively standard public health interventions can be effective, even for a pathogen with some capacity for human-to-human spread.

The study also highlighted factors associated with transmission. Patients with higher viral loads and evidence of liver injury were more likely to infect others, suggesting that biological factors alongside behavioural and environmental ones shape transmission risk. Interestingly, there was no clear association between overall disease severity and the likelihood of onward spread.

Another reassuring finding was the relatively limited impact of healthcare-associated transmission. Despite significant exposure, particularly early in the outbreak, only a small number of nosocomial transmission events were identified, and none involved healthcare workers. This suggests that standard IPC measures are likely to be effective.

Clinical presentation and IPC action

Hantavirus infection typically begins with non-specific symptoms: fever, myalgia, fatigue, and gastrointestinal upset before progressing rapidly in some patients to severe respiratory or renal disease. This non-specific early phase, combined with the rarity of the condition in the UK, makes early recognition difficult. Diagnosis depends heavily on taking a careful travel and exposure history.

If Andes hantavirus is suspected, early escalation to HCID pathways and rapid engagement with public health teams become essential.