Laboratories are leveraging established diagnostic and surveillance tools to track the Andes hantavirus outbreak linked to a recent cruise ship cluster.
By Alyx Arnett
When a cluster of Andes hantavirus infections was identified aboard a cruise ship returning from South America, public attention turned to questions about transmission risk and pandemic potential. But laboratory experts say the outbreak is not an unknown scenario and that existing laboratory and public health tools are helping officials track and understand the virus.
“We should definitely respect this virus and not trivialize it, but also not catastrophize it,” says Bobbi S. Pritt, MD, MSc, FCAP, professor of laboratory medicine and pathology and chair of the division of clinical microbiology at Mayo Clinic. “We have no evidence of sustained community transmission outside of close contact settings, no evidence of efficient airborne spread in public spaces, and no recommendation for general travel restrictions.”
During a media briefing hosted by the College of American Pathologists (CAP), a panel of pathologists and microbiologists discussed the outbreak, including person-to-person transmission risk, quarantine protocols, and the role of serology, PCR, and next-generation sequencing in confirming cases and monitoring the virus.
A Known Virus in an Unusual Setting
The Andes hantavirus is not new. The virus has circulated in Argentina and Chile for decades, and previous outbreaks have been well documented. What made this outbreak unusual was the setting: a cruise ship, where prolonged close contact between passengers may have facilitated person-to-person transmission.
Mara Jana Broadhurst, MD, PhD, FCAP, associate professor at the University of Nebraska Medical Center and member of the CAP Microbiology Committee, emphasizes that researchers and public health officials were not starting from scratch.
“An important difference with this outbreak is that this virus is an endemic virus to South America that has been studied for decades,” she says. “There is more information at the outset that helps us to understand how this virus is transmitted and what these risks are than what we had at the start of the COVID-19 pandemic.”
The Andes strain is unusual among hantaviruses because it can spread between people, although panelists during the CAP briefing say transmission requires prolonged close contact rather than casual exposure.
Benjamin Bradley, MD, PhD, FCAP, vice chair of the CAP Microbiology Committee and medical director at ARUP Laboratories, notes that cruise ship outbreaks can provide insight into transmission dynamics because exposures occur in a relatively contained environment. But he says the outbreak has not shown the level of transmissibility associated with viruses capable of widespread community spread.
Public health investigators believe the initial cases were likely linked to exposures in Argentina before passengers boarded the ship. According to the Associated Press, 11 cases had been reported at the time of the briefing, including nine confirmed infections.
Quarantine and Monitoring
The outbreak has also raised questions about how exposed passengers are being monitored, with some individuals quarantining at home while others are being monitored at The National Quarantine Unit at the University of Nebraska Medical Center. The CAP panelists say the approach reflects current understanding of how the virus spreads and the importance of symptom monitoring during the incubation period, which can last as long as six weeks.
Broadhurst, who is based at the University of Nebraska Medical Center—home to the national quarantine unit—says there is currently no evidence of transmission from asymptomatic individuals.
“We do not have evidence of transmission of this virus in asymptomatic people,” she says. “The most important thing is that people are aware that symptoms can develop within a pretty long incubation period.”
Broadhurst says symptom monitoring is a central part of the response strategy and notes that decisions about whether individuals remain in a quarantine facility or monitor at home are made collaboratively between public health officials and clinical teams.
“Being able to access appropriate care with the appropriate infection prevention and control precautions is very important,” she says.
Broadhurst says exposed individuals may need to be monitored for up to 42 days because of the virus’ long incubation period.
Diagnostic Testing: What’s Available and What Isn’t
For clinical laboratorians, one of the central questions raised by the outbreak is testing availability. Pritt says hantavirus testing remains specialized and is largely limited to public health, reference, and select academic laboratories.
Serology—particularly detection of IgM antibodies—remains the primary diagnostic approach once symptoms develop. Pritt notes that the Centers for Disease Control and Prevention (CDC) offers serologic testing and has made it available through select reference laboratories. She adds that Mayo Clinic Laboratories is working to make hantavirus serology testing available through physician orders, although testing outside referral settings remains limited.
PCR-based testing is also being used for case confirmation and epidemiologic investigations. Broadhurst notes that some existing laboratory tools developed for Sin Nombre virus—the hantavirus strain endemic to North America—may also detect Andes hantavirus because of similarities between the viruses.
“There is some pre-existing capacity and laboratory tools available,” she says.
The panelists also highlighted the role of next-generation sequencing in the response. Pritt says sequencing helped identify the Andes strain involved in the outbreak and compare viral sequences from infected individuals to help confirm epidemiologic links between cases.
“I think we can’t emphasize enough the importance of pathologists and laboratory medicine in effectively managing this outbreak,” she says.
Bradley cautions against broader public testing outside appropriate exposure scenarios. He notes that hantavirus serology can show cross-reactivity between related strains, increasing the risk of false-positive results in low-risk individuals. “This is not something that, if you saw a mouse in your house yesterday, you should go to your provider and ask for hantavirus testing,” he says.
The Domestic Angle: Hantavirus in North America
While the current outbreak involves the Andes strain, the briefing also addressed hantavirus risks in the United States. The Sin Nombre virus, first identified in the Four Corners region in 1993, remains the primary hantavirus concern in North America. Unlike Andes hantavirus, Sin Nombre virus is not known to spread person to person.
Pritt says most US hantavirus infections are associated with exposure to rodent urine, feces, saliva, or contaminated nesting materials, particularly in enclosed spaces where rodents have been present.
“The concern is that rodents, especially in enclosed places that have been abandoned or are not being used, can build their nests,” she says.
Pritt says individuals cleaning areas with rodent droppings or nesting materials should follow established safety precautions, including the use of gloves, respiratory protection, and disinfectants such as bleach solutions. She notes that guidance from the CDC and the World Health Organization outlines recommended cleaning and exposure prevention procedures.
Panelists during the briefing say that these types of exposures remain relatively uncommon and differ significantly from the person-to-person transmission concerns associated with the current Andes hantavirus outbreak.
Mutation Concerns and Genomic Surveillance
Questions about potential viral mutations also came up during the briefing. Bradley says he had not seen evidence of significant genetic changes in the sequences available so far and points to next-generation sequencing as an important tool for monitoring the outbreak.
“We are able to genotype these viruses in near real time and share that public health data,” he says.
Broadhurst adds that publicly available sequence data indicate the outbreak strain closely resembles previously characterized Andes hantavirus strains from South America. “That is reassuring that we can take lessons learned from prior infections and outbreaks in Argentina and Chile and extend those lessons into this current outbreak,” she says.
Pritt also notes that prior Andes hantavirus outbreaks in Argentina, including some involving larger numbers of cases, did not appear to produce mutations that substantially changed the virus’ transmission patterns or behavior.
The Lab’s Role in What Comes Next
For clinical laboratory professionals, the outbreak highlights several broader operational considerations, including cross-reactivity between related viruses, the limitations of serology in low-prevalence settings, and the expanding role of sequencing in infectious disease surveillance and outbreak response.
Pritt emphasizes that both conventional and advanced laboratory methods were important in the early stages of the response.
“[These methods] allowed us, in this case, to very quickly identify the cause of this outbreak,” she says.
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