Cruise ships are convenient floating hotels by which to see far-flung parts of the world – but as an epidemiologist, I know they are also everything an infectious pathogen could want: thousands of strangers packed into enclosed spaces for days or weeks, sharing dining rooms and high-touch surfaces such as elevator buttons and handrails, breathing recirculated air.

Each new port of call where passengers can explore for a few days is an opportunity for germs to embark – and once they do, they encounter a highly efficient setting for hopping from host to host.

The MV Hondius confirmed this well-known fact in April 2026, when an outbreak of Andes hantavirus began aboard the Dutch-flagged expedition vessel carrying 147 passengers and crew from 23 countries.

The Andes virus is one of several species of hantaviruses. It is the only one known to spread from person to person, though it doesn’t do so very efficiently. It is far less contagious than COVID-19 or the measles.

As of May 14, a total of 11 cases, including three deaths, have been reported in the Hondius outbreak.

Outbreaks at sea are one of the oldest problems in public health. From medieval plague quarantines to modern times, they have repeatedly tested the ability to control infectious disease – and have played a key role in shaping the international public health framework in place today.

That interconnected public health system, however, depends on the cooperation of countries around the globe.

From harbor quarantine to global disease control

The word “quarantine” was first documented in the English language in 1663, in the Oxford English Dictionary, which defined it as a period of 40 days during which people who might spread a contagious disease are kept isolated from the rest of the community.

The first official quarantine, though, came earlier, in 1377, when the Republic of Ragusa – modern-day Dubrovnik, Croatia........

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