Oh, ship. The Centers for Disease Control and Prevention (CDC) is now investigating what appears to be an outbreak of vomiting and diarrhea on Holland America's Zaandam cruise ship.
The 781-foot boat was scheduled to travel around Alaska and then down to Seattle from June 18 to July 2, 2018. Apparently, at least 58 (or 3.94%) of the 1,472 passengers and 15 (2.54%) of 591 crew members became ill with vomiting and diarrhea as the predominant symptoms. As of today, the CDC web site still lists the causative agent as unknown, but such a situation does sound suspicious for a norovirus outbreak.
Add the Zaandam to the CDC list of infectious disease outbreaks on cruise ships so far this year:
| Cruise Line | Cruise Ship | Sailing Dates | Causative Agent |
|---|---|---|---|
| Holland America Group | Zaandam | 6/18 – 7/2 | Unknown |
| Silversea Cruises | Silver Shadow | 5/10 – 5/24 | Unknown |
| Celebrity Cruises | Celebrity Infinity | 4/17 – 5/2 | Unknown |
| Cunard Line | Queen Victoria | 2/21 – 3/9 | Enterotoxigenic E. coli (ETEC) |
| Azamara Club Cruises | Azamara Quest | 1/25 – 2/8 | Unknown |
| Princess Cruises | Island Princess | 1/9 – 1/24 | Norovirus and Campylobacter |
Note that this list does not encompass all of the outbreaks that have occurred on boats this year. It only includes cruise ships that fell within the purview of the CDC's Vessel Sanitation Program (VSP), had voyages lasting 3 to 21 days long, and carried 100 or more passengers and outbreaks where 3% or more of passengers or crew reported symptoms of gastrointestinal (GI) illness to the ship’s medical staff. For example, if you had the runs while on a rowboat on a date, it would not have been on this list. Also, Gilligan and Mary Ann having GI symptoms while on the SS Minnow's 3-hour tour wouldn't have counted.
As you can see from the fourth column of the table above, definitively identifying the specific virus or bacteria that caused an outbreak can be challenging. Bacteria and viruses don't tend to fill out paperwork before they board the ship, and investigators may not be able to find the exact food or objects that were contaminated. As a CDC website describes, norovirus is the culprit in over 90% of cruise ship GI illness outbreaks where the cause is confirmed. Other common culprits are Salmonella spp., enterotoxigenic Escherichia coli, Shigella spp., Vibrio spp., Staphylococcus aureus, Clostridium perfringens, Cyclospora cayetanensis, and hepatitis A and E viruses. GI illness outbreaks aren't the only infectious disease outbreaks that may occur on cruise ships. There have also been reported outbreaks of the flu, Legionnaire's disease, measles, rubella, meningococcal disease, and vector borne diseases such as dengue and malaria.
So what precautions can you take to avoid getting sick on a cruise? Keep in mind that going on a cruise doesn't necessarily put you at higher risk for getting a GI illness or other diseases compared to many more regular activities such as going to a restaurant, a party, school, work, or a day care center. The close quarters and the shared meals and environment over an extended period of time on a cruise can help a pathogen spread. Nonetheless, the vast majority of cruises don't seem to have any outbreaks, and cruise ship outbreaks only represent a small fraction of the total number of GI illness outbreaks that occur throughout the year. For example, previously for Forbes, I mentioned our study published in PLoS ONE that quantified the global burden of norovirus.
Therefore, don't let news of an outbreak alone dissuade you from taking a cruise. However, consider taking the following precautions when you want to go a cruising:
- Search for the cruise line on the CDC's Vessel Sanitation Program (VSP) inspection database: Beware of any cruise line that got a score of lower than 85 on its inspections. The database does not include every single craft that goes on to the water, only ships that "carry 13 or more passengers" and "have a foreign itinerary with U.S. ports." Of course, a great inspection record is no guarantee that an outbreak won't happen. Even if a cruise line does everything it can to prevent an outbreak, a single passenger could still bring norovirus or another pathogen on to the ship. However, a poor inspection record could mean higher risk.
- Pay attention to where and when outbreaks are occurring: Naturally, you don't want to seek a ship where an outbreak is actively occurring. That would be like desperately seeking diarrhea. If an outbreak has occurred on a cruise line, make sure that they have taken the appropriate measures to clean the ship.
- Wash your hands frequently and thoroughly: You should do this in general and not just on cruise ships. Washing your hands with soap and water is preferable to using hand sanitizer.
- Avoid touching your face: You know that song, "Can't Feel My Face"? Well, you shouldn't be feeling or touching your face (or your eyes, ears, nose, or mouth) without washing your hands first.
- Get vaccinated: Why not protect yourself against diseases such as influenza, hepatitis A, and the measles? Taking supplements isn't going to help you here.
- Check for general hygiene and sanitation on the cruise ship: Are crew members and employees regularly washing their hands? Is trash being properly disposed? How clean are the kitchens and food serving areas? How often are the rooms and bathrooms cleaned?
- If you see someone vomiting or diarrhea-ing, keep your distance and report it to the cruise staff: You're probably well aware that throwing up is not the universal sign for "come give me a hug." But keep in mind that norovirus is highly infectious and can survive many routine cleaning procedures.
- Tell the medical staff if you get sick: If you caught a bug on a ship, you may be entitled to a refund or be able to postpone your cruise to a later time. Before you even book a cruise, check the cruise line's policies, and stick to reputable cruise lines that have established plans on how to prevent and deal with outbreaks.
- Make sure that your food is properly protected: Notify staff if anyone is coughing into the buffet or using their hands, mouth, or other body parts to scoop food into their plates.
- Keep your immune system working well: Get appropriate amounts of rest and sleep, stay well hydrated, and don't drink too much alcohol.
Certainly, nothing can ever completely eliminate the risk of a norovirus or other GI pathogen outbreak. Therefore, don't be too paranoid, and don't let fear prevent you from taking a cruise. However, taking the above-mentioned steps can help reduce your risk. After all, your cruise may be full of ship but you don't want it to be full of certain other things.
