Deadly outbreaks on cruise liners echo history of infectious diseases spreading aboard ships, from the Black Death to COVID.
From Black Death to Covid, ships have long hosted outbreaks. A deadly outbreak on a cruise liner is just the latest in a long history of infectious diseases spreading rapidly in the cramped confines of ships, from the Black Death to COVID-19. The recent hantavirus scare on a cruise ship left three dead and infected at least seven more passengers, highlighting how enclosed environments can facilitate virus spread.
The worst place to have an epidemic is in close quarters far from help, such as a ship on the high seas," US historian Alfred Crosby once wrote about the Spanish influenza pandemic of 1918. Ships remain enclosed environments where there is prolonged, repeated and close contact, which facilitates the spread of some outbreaks, particularly those transmitted through the air or via food.
Jean-Pierre Auffray, honorary president of the French Society of Maritime Medicine, ships pose a twofold risk: passengers and crew can transmit diseases to each other on board, while infected individuals may transport their illness across land. "The risk is twofold," he said.
The Andes strain of hantavirus, which spread onboard the MV Hondius cruise ship, can be transmitted via aerosols. Ships are ideal environments for viruses like influenza and COVID-19 to thrive due to close quarters and repeated contact among passengers and crew.
Historically, ships have been vectors for pandemics. In 1347, sailors from Genoa laid siege to the Crimean trading hub of Caffa when they became infected by plague-ridden corpses catapulted over the walls by the Mongol Golden Horde. When these sailors returned home via the Mediterranean, they brought with them a plague that devastated Europe.
"Ships remain enclosed environments where there is prolonged, repeated and close contact, which facilitates the spread of some outbreaks," Auffray explained. "We learned from the COVID pandemic, and there have been improvements on cruise ships. We've improved the ventilation systems, which allow us to better combat aerosol transmission."
However, even with these measures in place, infected passengers disembarking can still pose a risk. Before the MV Hondius docked in the Canary Islands, local governments initially opposed taking it in due to concerns about disease spread. In previous centuries, quarantined ships were kept away from ports, sometimes forced to dock at tiny islands called lazarettos.
"Ships remain enclosed environments where there is prolonged, repeated and close contact, which facilitates the spread of some outbreaks," Auffray said. "We've improved the ventilation systems, which allow us to better combat aerosol transmission."
While sailors on military ships are often young and fit, cruise ship passengers tend to be more elderly and vulnerable. However, viruses spread in similar ways: in close quarters where people regularly share equipment.
"Ships remain enclosed environments where there is prolonged, repeated and close contact, which facilitates the spread of some outbreaks," Auffray added. "We've improved the ventilation systems, which allow us to better combat aerosol transmission."
The latest incidents underscore how ships can be ideal environments for viruses to spread. While diseases can now hop continents on airplanes, most of human history saw them cross seas on boats. Ships remain a critical vector in the global spread of infectious diseases.
