An unknown illness has occurred onboard the Royal Caribbean cruise ship Navigator of the Seas, which has sickened more than 140 passengers and crew members, according to the U.S. Centers for Disease Control and Prevention (CDC). The outbreak was on the second day of a weeklong round-trip cruise from Los Angeles that left on July 4, 2025. The ship reported the sick passengers to the C.D.C. as soon as it arrived back in Los Angeles on July 11, after visiting Mexico.

The outbreak struck 134 of the 3,914 passengers and 7 of the 1,266 crew members on board, according to the CDC’s Vessel Sanitation Program. The symptoms included diarrhoea, vomiting, and abdominal cramps – associated with the sort of gastrointestinal illnesses that are frequently reported on board cruise ships. The CDC said the source of the illness is unknown, but norovirus is frequently to blame for such outbreaks on cruise ships, though more testing is necessary.

How Royal Caribbean Has Responded to the Outbreak

Royal Caribbean activated its outbreak prevention and response protocol in light of the illness. The company also “steps up our already rigorous sanitation practices,” including “increased sanitation of touchpoints throughout the ship,” and “a procedure that targets high-touch areas such as handrails, doorknobs and elevator buttons, which are already being frequently disinfected, among others.” In addition, the cruise line quarantined sick passengers and crew members to contain the illness, and the sailors gathered stool specimens for testing to assist in determining the cause of the outbreak.

Though the crew has moved briskly in response, the outbreak has raised questions about the health and safety measures aboard cruise ships. The CDC’s Vessel Sanitation Program examined the outbreak and maintains an ongoing working relationship with Royal Caribbean to determine the etiology of the illness and to address subsequent cruise line actions to mitigate this outbreak.

Gastrointestinal Outbreaks Aboard Cruise Ships

Source Gastroenteritis, including norovirus, is a challenge the cruise industry frequently has to face. These highly communicable viruses can also spread fast in confined spaces, such as a cruise ship, where lots of people have to use the same spaces. Norovirus, often referred to as the “stomach flu,” has been a problem on cruise ships for several years, and the CDC closely watches for outbreaks to make sure cruise lines comply with standards for cleanliness.

Gastrointestinal illness outbreaks are relatively frequent, but the CDC’s presence in a situation like this underlines the need for reporting and surveillance. Cruise lines must report outbreaks to the C.D.C., which in turn said it worked to track trends and ensure appropriate health measures. The agency also offers recommendations on prevention interventions such as improved sanitation, isolation of ill passengers, and health measures for affected individuals.

Historical Outbreaks and Trajectory in the Cruise Industry

The outbreak on Navigator of the Seas is not the only recent one of illnesses on a cruise ship. Other cruise lines also had earlier outbreaks this year, raising questions about how the cruise industry can effectively manage public health aboard its ships. In February 2025, nearly 80 passengers on a Holland America Line ship got sick, as did more than 80 passengers and crew members on a Princess Cruises ship. Another outbreak occurred on a Cunard luxury ship on an international voyage, in which more than 240 passengers and crew members were affected.

The outbreaks are the latest in a series of gastrointestinal illness episodes on cruise ships that have raised questions about the cruise industry’s capacity to contain the spread of infectious illnesses in large vessels. But while the cases are far-ranging, experts say outbreaks like these remain rare in contrast to the millions of passengers who safely vacation on cruises each year.

CDC’s Role in Monitoring and Preventing Cruise Ship Illnesses I want to say a few words about the CDC’s role in monitoring and preventing illnesses onboard cruise ships.

The CDC’s Vessel Sanitation Program is instrumental in the surveillance and control of GI illness outbreaks during cruise travel. The program is designed to help ensure that ships maintain the highest sanitation standards in order to prevent the spread of infectious diseases. The CDC also offers information and recommendations for cruise lines to help in the prevention of illness before it happens.

The CDC also conducts inspections of cruise ships to verify that appropriate health and safety protections have been instituted. These include checks of food handling, water quality, and cleanliness — everything that is essential to prevent sicknesses from spreading. In addition, the CDC collaborates with cruise lines on ways to enhance health measures, including training crew members on the detection and treatment of potentially sick passengers.

What Passengers Should Know

For those who are ready to cruise, however, here is all that you need to know about cruisers’ illness outbreaks, particularly during the peak travel period. Travelers should observe effective hygiene measures, including regular hand washing and use of alcohol hand gels, particularly in buffet-style restaurants and amongst residents in public areas. Passengers and crew members are also encouraged to avoid close contact with passengers who show signs of illness and notify the ship’s medical staff immediately if symptoms develop.

Travellers who are worried about getting ill should check the CDC’s Vessel Sanitation Program page to see recent health inspection reports for individual cruise ships. Travelers may also ask the cruise line what it is doing to ensure a healthy and safe journey.

Conclusion: Continuing to Address Health Security for Cruise Ships

The latest outbreak on Navigator of the Seas is one example of the continued challenges the cruise industry has faced in protecting health and safety. This is troubling, no question, but also offers the cruise industry another chance to fine-tune health protocols and take yet another step to protect passengers and crew. Alongside continued monitoring from the CDC and stronger ship sanitation and illness prevention methods from the cruise industry, the hope remains that future outbreaks can be limited, and travelers can continue to vacation safely and healthily at sea.

(Source: Centers for Disease Control and Prevention, Royal Caribbean International)