Could Andes hantavirus spread more easily than officials admit? Scientists debate uncertainties after MV Hondius outbreak

The outbreak of Andes hantavirus linked to the cruise ship MV Hondius has triggered renewed scientific debate over a difficult public health question: Are authorities oversimplifying how the virus spreads in order to prevent panic?

While health agencies continue to stress that the virus remains far less contagious than Covid-19, several researchers studying hantaviruses say important uncertainties still exist — particularly regarding whether transmission can occur before symptoms appear or after only brief contact.

The outbreak aboard the Dutch expedition vessel has infected at least nine people and caused three deaths, drawing international attention to one of the world’s rarest human-transmissible viruses.

What makes the Andes hantavirus unusual?

Most hantaviruses spread to humans through exposure to infected rodent urine, saliva, or droppings. Human-to-human transmission is considered extremely rare.

However, the Andes strain — found mainly in parts of South America including Argentina and Chile — is the only known hantavirus confirmed to spread between people.

Health officials, including the World Health Organization and US public health authorities, have repeatedly stated that transmission typically requires prolonged close contact with someone who is visibly ill.

Officials also maintain that asymptomatic individuals are unlikely to spread the virus.

But according to scientists cited in a recent report by The New York Times, the scientific evidence may not be fully settled.

Scientists warn there are still major unknowns

Some researchers believe infected patients could become contagious shortly before symptoms emerge, or during the very early phase of illness.

Others argue there is limited but concerning evidence that transmission might occasionally happen without sustained physical interaction.

The concern stems partly from earlier outbreaks in Argentina between 2018 and 2019, where researchers tracked 34 infections and 11 deaths linked to the Andes virus.

Investigators identified several “super-spreading” events in which one infected person appeared to infect multiple others.

A few cases reportedly involved individuals who had only minimal or brief contact with infected patients. One possible transmission was linked to a short interaction between two people crossing paths.

These observations have led some scientists to explore whether aerosol or airborne spread might occasionally occur under rare conditions.

Because hantaviruses are commonly contracted through inhalation of virus particles from rodent waste, some virologists argue that airborne human transmission cannot be entirely ruled out scientifically.

Why are health agencies cautious

Public health agencies appear concerned that openly discussing uncertain or rare transmission possibilities could create disproportionate fear.

WHO Director-General Tedros Adhanom Ghebreyesus reportedly said that authorities focus public messaging on the most common transmission routes because communicating rare exceptions can easily confuse the public.

This reflects a broader challenge in outbreak communication: balancing scientific uncertainty with the need for clear guidance.

Some scientists, however, argue that downplaying uncertainties may ultimately weaken public trust if new findings later emerge.

Researchers quoted in the report said uncertainty itself should be communicated transparently, especially when dealing with emerging or poorly understood infectious diseases.

Why experts say this is not another Covid-style threat

Despite the debate, infectious disease experts continue to stress that the Andes hantavirus does not spread efficiently between humans.

The limited scale of the MV Hondius outbreak is itself viewed as reassuring.

Roughly 150 passengers spent extended periods together aboard the vessel, yet only a small number of infections have been confirmed so far.

That pattern suggests transmission remains relatively difficult compared with highly contagious respiratory viruses such as SARS-CoV-2.

Scientists also note that hantavirus infections are generally severe and symptomatic, which makes outbreaks easier to detect and contain through isolation and contact tracing.

A reminder about emerging disease uncertainty

The MV Hondius incident has highlighted how even decades after discovery, some viruses remain only partially understood.

The debate is less about whether the Andes hantavirus is becoming a pandemic threat — most experts believe it is not — and more about how public health authorities should communicate scientific uncertainty during outbreaks.

For now, researchers say the overall public risk remains low. But the outbreak serves as a reminder that emerging infectious diseases often involve unanswered questions, evolving evidence, and difficult communication choices for health officials worldwide.