The latest case of a Canadian passenger testing positive shows the hantavirus outbreak isn't over yet. We can probably expect more cases, given the long incubation period of this infection.
More than 120 passengers from the stricken cruise ship MV Hondius are now being monitored in their home regions, including five Australians and a New Zealander who will remain in quarantine for three weeks in a facility near Perth.
But while caution is still needed , the outbreak is likely to be contained and provides a vivid reminder of the importance of a globally coordinated response to such pandemic threats.
The parallels with the start of the COVID pandemic are obvious. The Andes hantavirus shares a number of frightening features that have understandably raised fears across the globe.
It originated from an animal-human spillover, it can spread from person to person and a cruise ship had an amplifying effect.
Its ability for animal-to-human (zoonotic) transmission from its natural rodent reservoir to unsuspecting tourists makes the hantavirus an unpredictable threat.
The animal-human spillover capability has been observed with multiple hantavirus species that occasionally infect people across the Americas, Europe and Asia. What distinguishes the Andes virus is its ability for person-to-person transmission . This is a critical feature needed to start a pandemic.
Its other alarming characteristics are the extremely high case fatality risk of 21-36% and its long incubation period (median 18 days, range of 7-39 days). The latter allows cases to disperse widely before becoming ill and requires a lengthy period of quarantine for contacts.
Why this will not be the next pandemic
The World Health Organization's ( WHO ) rapid international response and the hantavirus' transmission dynamics are important factors in preventing the outbreak from becoming a global pandemic.
Unlike COVID, the Andes virus was already known to scientists and public health authorities.
While it can spread from person to person, the importance of such transmission remains uncertain, according to a recent systematic review . Transmission is also concentrated around the time a person develops symptoms , which rapidly get worse and effectively reduce further contacts and opportunities for spread.
For a significant outbreak of a virus like this, it needs to get lucky. If an infected person is attending a large gathering at the point they become infectious, they can transmit to multiple people in a "superspreading event".
A 2018 Andes hantavirus outbreak was seeded by a symptomatic person attending a party with around 100 guests, five of whom became infected. Something similar can be expected from an unwittingly infectious person in the confined environment of a cruise ship.
In stark contrast with COVID, mild or even asymptomatic infections are rare and the course of illness is quite rapid once symptoms develop. That leaves a narrow window for onward transmission.
The long incubation period helps with contact tracing for isolation and quarantine. Previous hantavirus outbreaks have been eliminated through these simple public health measures .
The rapid response coordinated by the WHO, using the International Health Regulations framework, was also critical for containment.
Key implications for improving health security
While this outbreak will likely be eliminated, there are still too many gaps in global pandemic prevention, preparedness and response measures.
Probably the single most important action is to reinforce the critical role of the WHO in leading the multilateral cooperation central to global pandemic prevention and control. As its Director-General Tedros Adhanom Ghebreyesus reminded policy makers , viruses don't care about policies or borders.
Supporting the roll-out of the revised International Health Regulations and the Pandemic Agreement is also critical.
The 2024 revisions to the regulations came into force in September last year. But 11 of the 196 member states rejected the amendments (though these rejections may be withdrawn at any time). The Pandemic Agreement has been adopted by the WHO, but some refinement is needed before it comes into effect.
The recent withdrawal of the United States and Argentina from the WHO and funding cuts by other members present a significant barrier, leaving the world less prepared for the next spillover event.
Other preventive measures
This outbreak is a reminder of the need for precautionary measures to reduce airborne transmission of emerging infections with a history of person-to-person transmission, particularly on cruise ships and similar confined settings which can rapidly amplify transmission. Consequently, we need action to improve indoor air quality and the use of respirator-type masks .
It also highlight the importance of transparent, timely and effective communication, particularly to counter the rush of misinformation that follows outbreaks. Within hours of the first news, social media teemed with baseless claims .
We need renewed research efforts to understand and manage human-driven ecological changes - including deforestation, agricultural expansion, wildlife trade and climate change - that raise the risk of viral spillover from animals to people.
The MV Hondius outbreak is a stark warning. It shows how a lethal zoonotic virus can emerge unexpectedly and rapidly disseminate across the globe via travellers.
The next pandemic could start quickly if the world isn't prepared. We have hopefully "dodged a bullet" with this hantavirus outbreak but may not be so fortunate next time unless we increase political and economic investment in shared global health security.
Bill Hanage has received funding from the National Institutes of Health, the Gates Foundation and the Morris-Singer Foundation. He has served on advisory boards and acted as a Consultant for Merck Vaccines and Shionogi Incorporated.
Michael Baker does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
