As post-pandemic travel continues to surge, an increasing number of Americans are flooding back to cruise ships this summer — but some cruise lines are dealing with an unwelcome passenger on board: norovirus.
Cases of the highly contagious virus that causes diarrhea and vomiting spiked this winter and spring in the United States following a lull during the COVID-19 pandemic. As infections spread on land, multiple cruise ships have been hit with the stomach bug at sea.
Cruise ships and norovirus
In May, an outbreak of norovirus on a Celebrity Summit cruise ship sickened more than 150 passengers and 25 crew members, according to the U.S. Centers for Disease Control and Prevention, which tracks outbreaks of gastrointestinal illness on cruise ships through its Vessel Sanitation Program (VSP).
This is the third outbreak of norovirus on a Celebrity Cruises ship this year — another popular cruise line, Royal Caribbean International, has reported 4 outbreaks to the CDC since January.
In total, the CDC has reported 12 outbreaks of vomiting and diarrhea on cruise ships (10 confirmed as norovirus and two of an unknown cause) during 2023 so far — that's more outbreaks in six months than the yearly total in 2017, 2018 and 2019.
Norovirus can spread year-round, but it tends to have a wintertime seasonality and peak during the colder months — outbreaks are most common between November and April, TODAY.com previously reported.
"It's a virus we typically see all throughout spring, so it’s not unusual to be see cases in April and May, (and) we are continuing to see many cases now," Dr. Luis Ostrosky, an infectious disease specialist at UTHealth Houston and Memorial Hermann in Houston, tells TODAY.com.
However, as travel surges this summer, travel-related illnesses are expected to surge, as well. “I think our travel frenzy after COVID is partially fueling this continued spread (of norovirus),” says Ostrosky.
What should people know about norovirus and how to avoid getting sick on cruise ships this summer?
Norovirus symptoms and treatment
The most common symptoms of norovirus are vomiting, nausea, diarrhea and abdominal pain, Dr. Albert Ko, infectious disease physician and professor of public health, epidemiology and medicine at Yale School of Public Health, tells TODAY.com.
Less commonly, norovirus may cause a headache, muscle aches, or a low-grade fever — symptoms usually develop within one to two days after exposure to the virus, per the CDC.
In the vast majority of people, norovirus symptoms will last several days and resolve on their own.
There’s no specific treatment or antiviral for norovirus, according to Ostrosky, but most cases can be managed at home with supportive care like hydration and rest. Sick people should also isolate until their symptoms resolve, the experts emphasize.
Some people are at higher risk of developing severe norovirus symptoms — these include infants, the elderly, and people with compromised immune systems, Ostrosky noted.
How does norovirus spread?
Norovirus is highly contagious and can spread directly through sick people and contaminated surfaces, food, or drinks.
Transmission often occurs when tiny virus particles in feces or vomit from an infected person end up in another person's mouth through direct contact or by touching contaminated surfaces and putting unwashed hands in the mouth or nose, TODAY.com previously reported.
Norovirus can also get into food before, during or after preparation, and it's the top germ causing foodborne illness in the U.S., per the CDC. Virus particles can contaminate drinking water that isn't treated properly or pools when people poop in the water.
It only takes a small number of virus particles for norovirus to spread, which is why norovirus causes so many explosive outbreaks, Ko previously told TODAY.com.
Exposure to less than 100 norovirus particles can make someone sick, and infected people typically shed billions of particles, according to the CDC.
Most people are infectious from symptom onset until about two or three days after recovering but some people can remain contagious for weeks, Ko notes. People can get infected with norovirus multiple times in their lifetime.
Is norovirus common on cruise ships?
Certain environments are more conducive to the virus spreading. According to the CDC, the most common settings for norovirus outbreaks are healthcare facilities, restaurants or catered events, schools, daycares, and of course, cruise ships.
Cruise ships are often associated with norovirus because of the enclosed spaces, close living quarters, communal dining, and high turnover of passengers, experts note. That said, outbreaks of acute gastrointestinal illnesses are relatively infrequent on cruise ships compared to settings on land, the CDC notes.
How to avoid norovirus on a cruise
Hand hygiene is key to prevent the spread of the highly contagious virus — but the way you clean your hands matters, experts note. It has to be with soap and water, because alcohol-based hand sanitizers are not effective against norovirus.
“Norovirus is one of the few viruses that doesn’t get deactivated by alcohol. You actually need to use soap and water to physically destroy it and remove it from your hands,” Ostrosky previously told TODAY.com.
It's important to wash your hands with soap and clean water frequently, but especially after using the bathroom or changing diapers, before eating, and before touching your face.
Surfaces or objects that are contaminated with norovirus can be cleaned with a high-level disinfectant like bleach, per Ostrosky.
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