90-Second Read: I Know Way Too Much About Infectious Diseases. Here’s Why I’m Considering Taking a Cruise With My Family Anyway.

That's not even the only cruise in the news right now for public health reasons, a norovirus outbreak on a ship called Ambition recently made dozens of passengers sick shortly after the trip began. A study of a 105-day, around-the-world cruise found that about 20 percent of the passengers visited the ship's doctor for an infection, mostly respiratory or gastrointestinal. If you've got a cruise booked, it's perhaps worth thinking about how you might reduce your risk of infectious disease. At one point, the luxury ship accounted for a remarkable 50 percent of all confirmed coronavirus cases.

A 2022 study gave participants contact-tracing devices to estimate how many close contacts they had each day while on a cruise, basically, evaluating the likelihood of an infectious disease's spread. They found that the average cruise ship passenger had a total of 20 unique close contacts a day, despite measures on the ship in question to try to reduce the number of COVID-19 cases aboard. For example, in the case of the cruise with norovirus, the French authorities temporarily prevented anyone from getting off the ship, leaving passengers trapped on the vessel with norovirus. From a theoretical perspective, cruises are absolutely great places for illnesses to thrive.

With Hantavirus, the incubation period can take up to six weeks, so people must be isolated for a really long time to ensure they won't get sick and start infecting others. Many cruise lines require travelers to isolate in their cabins if they have an infectious disease, sometimes even after they recover, if the cruise is still going. In other words, cruise ships almost definitely pose a high risk for infection, but it's hard to assess exactly what that risk looks like in practice. We know that diseases can and do spread easily between people on cruises, but how much worse they are than in general life is hard to evaluate for sure.

Some of those cruises are also famous in the scientific literature, one of the foundations of modern contact tracing comes from an outbreak of gastroenteritis on a cruise ship. Think about all the other ones passengers could bring with them when they embark on a cruise. But the issue with studies like this is that they tell us little about the true number of infections.