A Royal Caribbean cruise was just hit with a major norovirus outbreak. Why cruise ships are a breeding ground for the disease.

Dozens of people traveling on a Royal Caribbean cruise have been sickened due to a norovirus outbreak, the Centers for Disease Control and Prevention reported on Sept. 29.

At least 71 people have come down with the gastrointestinal illness aboard the Serenade of the Seas voyage from San Diego to Miami. The cruise set sail on Sept. 19 and is due to dock on Oct. 2.

Royal Caribbean said in a statement to USA Today that the health and safety of its guests, crew and the communities their cruise ships visit are its top priority. The company noted they implement “rigorous cleaning procedures, many of which far exceed public health guidelines” in order to maintain the healthiest, cleanest environment on board.

This outbreak is the 19th gastrointestinal illness incident on a cruise ship in 2025 to reach the CDC’s public reporting threshold — 3% or more of passengers or crew reporting symptoms of GI illness to the ship’s medical staff — surpassing the number of cases cruise ships saw in 2024. It’s another in a long string of outbreaks to make headlines: In April, the Queen Mary 2, a luxury cruise ship, saw more than 240 people sickened with norovirus. In February, the Holland America Line ship Rotterdam experienced a norovirus outbreak that affected nearly 120 people. The cruise line’s ship Eurodam, meanwhile, saw a norovirus outbreak in April that affected 170 people.

What is norovirus?

Norovirus is a highly contagious virus that causes gastrointestinal illness. Symptoms typically include diarrhea, vomiting, nausea and stomach cramps. Norovirus usually lasts for one to three days, and people usually experience symptoms 12 to 48 hours after exposure, according to the Mayo Clinic.

Norovirus can be contracted by eating or drinking contaminated food or water, touching contaminated surfaces and then your mouth, or through close contact with an infected person.

The virus is shed in feces and vomit, and can live on surfaces for days and even weeks. It’s especially difficult to eliminate since it can survive hot temperatures and is resistant to many disinfectants, including hand sanitizer.

Why is norovirus so common on cruise ships?

The nature of cruise ships — where people are in close contact with others for a long period of time — means it’s easy for norovirus to spread, and for many people to fall ill with it at the same time.

“Norovirus is also known as the cruise ship virus because of its frequent outbreaks on cruise ships and military bases — and it’s circulating everywhere,” Dr. Craig Wilen, associate professor at the Yale School of Medicine, previously told Yahoo. “We have no drugs or vaccines for it, so it’s a major public health burden.”

While it’s difficult to totally avoid norovirus in a confined environment like a cruise ship, you should regularly wash your hands with soap and water, especially after using the bathroom or before preparing food. When cleaning, use bleach-based products that are effective at killing the virus.

Why people are concerned right now about norovirus on cruise ships

While cruise ships have long been associated with norovirus, recent developments have sounded alarm bells for people working in public health. In April, all full-time employees in the CDC’s Vessel Sanitation Program were laid off — part of Health and Human Services Secretary Robert F. Kennedy’s plan to remake the CDC and reshape health in America. The program, according to the CDC, “helps the cruise industry prevent and control public health issues.”

However, the CDC later said in a statement that the work is done by health officers who were “not subject to the reduction in force.”

In April, cruise ship trade organization Cruise Lines International Association told USA Today that since cruise inspectors program is “voluntary and funded by the cruise industry,” it will continue to operate. The program inspects cruise ships twice a year and the findings are available online.