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Scientists comment on a hantavirus update from the UK Health Security Agency (UKHSA) that two people from the UK are not reporting symptoms and are self-isolating.
Prof Ellen Brooks Pollock, Professor in Infectious Disease Modelling, University of Bristol, said:
“Clusters of Hantavirus usually involve a limited number of people, but as we’ve seen, infection is serious. Where person-to-person transmission has been documented, it is usually with sustained and close contact, so the risk to the general population is low. However, symptoms can take weeks to appear, so it’s important that the individuals that have returned to the UK refrain from close contact with others for a period of weeks.”
Dr Cariad Evans, Consultant in Virology / Infectious Disease, Sheffield Teaching Hospitals NHS Foundation Trust, said:
“It is reassuring that individuals who have been aboard MV Hondius during the infectious period have been identified and isolated, which is routine practice for case identification and management of an outbreak response. These individuals will be risk assessed to see if they had any direct contact with the confirmed cases, to understand the potential risk of transmission to them. Isolation at home and close monitoring by UKHSA is appropriate and standard practice for the management of potentially exposed individuals. As the UK contacts are currently asymptomatic, they should not pose a risk of onward transmission to others and therefore the risk to the UK public is very low.
“The main mode of transmission of Andes Hanta virus remains through contact with infected rodents or their urine, droppings or saliva. Reported cases of human to human transmission has been described with close and prolonged contact, particularly among household members or intimate partners, and appears most likely during the early phase of illness when there is a high viral burden (the patient is most infectious). This outbreak timeline suggests transmission may have occurred to some individuals onboard MV Hondius, a unique setting which would favour transmission if there has been continued use of shared bathrooms like a household setting or enclosed environments like shared cabins, which could lead to close contact with infectious virus from a symptomatic individual. The risk to individuals without direct/close environmental contact will remain very low. Overall, the exact mechanism of transmission in this outbreak remains unclear, as the outbreak remains under investigation.”
Dr Raymond Alvarez, immunologist, virologist, and CEO of Ichor Biologics (a biotechnology company developing antibody-based therapeutics for infectious diseases, including hantavirus) and formerly Assistant Professor at the Icahn School of Medicine at Mount Sinai, said:
Is it worrying that two people who were on board the MV Hondius have returned to the UK – what risk do they represent to the wider public?
“The return of individuals to the UK from the ship is not a cause for concern. This is a scenario that public health systems are designed to manage, and the measures outlined by UKHSA, self-isolation, monitoring, and contact tracing, are appropriate and effective.
“The key determinant of risk is the level and duration of contact these individuals may have had with suspected cases. Andes virus does not spread through casual contact; transmission, where it occurs, typically requires close, prolonged exposure, often around the early symptomatic phase.
“Until detailed exposure histories are fully assessed, there is some uncertainty. However, based on what we know about the virus and with appropriate precautions in place, the risk to the wider public remains very low.
“TLDR: With self-isolation and monitoring in place, and given that hantavirus does not spread through casual contact, the risk to the wider public remains very low. This is a controlled situation that reflects appropriate precaution rather than increased risk.
What do we know from evidence about the risk of onward transmission represented by people who may have been contacts of cases or onboard the ship, if they’re not showing symptoms?
“The risk of onward transmission from individuals who are not showing symptoms is considered very low, based on what we know about hantavirus. In the rare cases of human-to-human transmission, it typically requires close, prolonged contact with an infected individual, often around the early symptomatic phase rather than in people who are completely asymptomatic.
“The key factor in assessing risk for the two individuals in quarantine is whether they had any contact with confirmed or suspected cases, and the nature and duration of that contact. If they did not have close contact with symptomatic patients, their risk of both developing and transmitting infections are very low.
“TLDR: Asymptomatic contacts are very unlikely to spread hantavirus. Transmission, where it occurs, requires close, prolonged contact with someone who is already showing symptoms.
Is it sensible and evidence-based that these people are self-isolating?
“Yes, from my experience interviewing ID physician treating previous hantavirus cases in southern Chile, self-isolation in this context is both sensible and consistent with public health practice. In southern Chile, infectious disease physicians recommend that individuals who have had close contact with infected patients self-isolate and limit interactions for several weeks, reflecting the known incubation period of the virus. This is combined with ongoing monitoring for the development of symptoms and continuous diagnostic testing were possible. These are targeted measures aimed at reducing the already low risk of transmission in absence of symptoms.
Is person-to-person transmission of this virus easy/common, or is transmission still mostly from infected rodents in areas where the virus is endemic?
“In general, transmission of hantavirus is still overwhelmingly driven by rodent-to-human exposure, particularly through inhalation of aerosolized rodent excreta in endemic areas.
“While person-to-person transmission has been documented with Andes virus, these events are rare and context-dependent, typically requiring close, prolonged contact. It is not considered an efficient or common route of spread.
“Importantly, in the few well-studied outbreaks where human transmission did occur, standard public health measures, such as isolation and contact tracing, were effective at quickly reducing transmission, reinforcing that this is a limited and controllable pathway, and not a primary driver of viral spread. This is not a virus that spreads easily between people.
“TLDR: Hantavirus is still primarily transmitted from rodents to humans, not between people. While limited person-to-person spread has been documented with Andes virus, it is rare, requires close contact, and remains a controllable pathway rather than a common mode of transmission.”
Prof Jonathan Ball, Deputy Vice-Chancellor and Professor of Molecular Virology, Liverpool School of Tropical Medicine, said:
“This seems like a balanced approach. Evidence suggests that human to human transmission is possible, but the risk is low and requires very close contact.
“Self-isolation, and monitoring for the appearance of any virus-like symptoms – for example fever and aches – together with repeat testing over several weeks will help ensure early detection and prevent any risk of onward infection. But hopefully these two people have not been infected, and this turns out to be wise, albeit inconvenient, precaution.”
https://www.gov.uk/government/news/ukhsa-update-on-the-hantavirus-cruise-ship-outbreak
Previous SMC comments on hantavirus situation:
Declared interests
Prof Ellen Brooks Pollock: “I don’t have any funding from industry or conflict of interests.”
Dr Cariad Evans: “No conflicts of interest.”
Dr Raymond Alvarez: “Dr. Alvarez is the CEO and co-founder of Ichor Biologics, which is actively developing antibody therapeutics targeting hantavirus. He may therefore have a potential financial and professional interest in the development of treatments for this disease. He has received research funding and support related to antibody discovery and infectious disease research. He has no other relevant advisory roles, industry affiliations, or conflicts of interest to declare beyond those stated.”
Prof Jonathan Ball: “No CoIs.”