After an outbreak of gastrointestinal illness on Royal Caribbean’s Oasis of the Seas sickened hundreds of passengers, the cruise line has offered travelers full refunds for the cost of the cruise fare.

But cruise passengers generally have very little recourse if they get sick during a vacation. It’s difficult to prove the origins of food poisoning and any compensation is typically left to the generosity or goodwill of the cruise line in question.

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The Oasis of the Seas returned to Port Canaveral, Fla. on Saturday, a day earlier than scheduled, after gastrointestinal illness sickened 277 guests and passengers since the ship departed on Jan. 6, Royal Caribbean told MarketWatch. That number reportedly grew to nearly 500 people since then.

In a somewhat unusual move, the cruise line has decided to provide travelers with full refunds of their paid cruise fares. The 7-night Western Caribbean voyage on the Oasis of the Seas starts at $626 per person before taxes and fees for an interior stateroom.

“ ‘This is just crazy. We’re hunkered down in our room because I’m so scared of getting sick.’ ” — —Cruise Critic member Raycin

In addition to a full refund of the cruise fares, a letter allegedly delivered to the ship’s passengers noted that the company will provide up to $200 per person for re-booked domestic flights, up to $400 per person for international flight change fees or up to $200 per stateroom for one night’s stay at a hotel. Consumers need to contact Royal Caribbean to receive those reimbursements.

The company did not immediately confirm whether the letter was accurate.

The cruise line also said it will be refunding internet and beverage packages and prepaid gratuities on a prorated basis for the day the cruise won’t be sailing.

Passengers have noted in message boards on the travel site Cruise Critic that the ship’s crew was taking extra precautions to prevent further spread of the illness, including extra cleaning of public areas and preventing passengers from serving themselves at the buffets.

Still, some passengers have expressed frustration with the experience while the ship was still at sea. “This is just crazy. We’re hunkered down in our room because I’m so scared of getting sick,” Cruise Critic member Raycin posted. “This is our first cruise in 15 years and will most likely be our last.”

A spokesman for Royal Caribbean said the early return was designed, in part, to give the company more time to clean and sanitize the ship before its next sailing.

“We think the right thing to do is to get everyone home early rather than have guests worry about their health,” Owen Torres, corporate communications manager at Royal Caribbean, said in an email.

“ Cruise lines are under no obligation to provide a refund. ” — —Colleen McDaniel, executive editor at Cruise Critic

“Our guests sail with us to have great vacations, and we are sorry this cruise fell short,” he added.

In recent years, outbreaks of gastrointestinal illness have become less common. Last year, there were only 11 confirmed outbreaks, according to the Centers for Disease Control and Prevention, which left only 658 people ill.

Of those 11 outbreaks, only five were confirmed to be norovirus, one of viruses that most commonly causes gastroenteritis, which is the lowest figure in years.

“Considering 28 million took a cruise in 2018, the number of those who reported ill was a tiny fraction of those who took a cruise,” said Ben Souza, editor of travel website Cruise Fever.

Here is what cruise passengers need to know about what they can do if they get sick on a cruise:

Don’t expect a refund — even if you get norovirus

Cruise lines are under no obligation to provide a refund, said Colleen McDaniel, executive editor at Cruise Critic. Typically, they will provide compensation in the form of cruise credits for future sailings or onboard credit for the remaining duration of the cruise.

The choice to offer a full refund was somewhat unusual on Royal Caribbean’s part, as a result. “Cruise lines look at this sort of thing on a case by case basis and how disruptive this was to passengers,” McDaniel said. Given that Oasis of the Seas had to skip two ports of call and return a day early, McDaniel said it was abundantly clear to Royal Caribbean that the illness outbreak adversely affected passengers’ experience even if they weren’t sick.

“ Last year, there were only 11 confirmed outbreaks of gastrointestinal illness, which left only 658 people ill. ”

The company would not confirm what it has offered in the case of previous gastrointestinal illness outbreaks. But Miami-based cruise-industry lawyer Jim Walker said that following a large outbreak on the Explorer of the Seas back in 2014, Royal Caribbean only offered a 50% refund on the cruise fare and a 50% credit toward a future cruise.

“In most cases the cruise line will not offer any compensation, implying that it is the customers’ fault for not washing their hands, even though the CDC and the FDA state that contaminated food or water are the most common explanations for norovirus,” Walker said.

“ In 2014, Royal Caribbean only offered a 50% refund on the cruise fare and a 50% credit toward a future cruise. ”

Arguing for more in compensation can also be something of a fool’s errand. Walker said his law firm doesn’t even take on cases involving these outbreaks. “Don’t call us if you get sick on a cruise,” he said. “Establishing where the virus came from, or that the cruise line was negligent, is virtually impossible to prove.”

Also see: Running scared this flu season? 7 things you shouldn’t touch — including soap

Consumers’ best avenue for compensation is through travel insurance

Moreover, those who did fall ill while on board could be on the hook for the cost of any medical treatment they’ve received.

“Incidents like this illustrate why it’s a good idea to consider buying travel insurance before you go,” said Christine Sarkis, deputy executive editor of the travel site SmarterTravel.com.

For example, a travel-insurance policy with trip interruption coverage would help passengers defray the cost of returning home early. Other policies may also cover the expenses associated with medical treatment and an emergency evacuation from the ship if they are hospitalized while traveling.

Additionally, refunds like the one Royal Caribbean offered don’t always cover additional travel expenses incurred, such as rebooking airfare.

While on the ship, wash your hands

Passengers’ experience on the Oasis of the Seas is a strong reminder of the need to exercise good hygiene when traveling.

“Wash your hands,” McDaniel said. “Wash them before you eat, and wash them after you use the restroom.” That could help prevent the spread of illness, but may not be so helpful, however, if the contamination came from the kitchen.

Buffets can be a hotbed of germs: If you see someone grab food from the buffet with their hands rather than a utensil, they should notify the ship crew to ensure that the potentially-tainted food is disposed.

Shares of Royal Caribbean RCL, -5.61% have dropped around 18.6% year-over-year. Comparatively, the Dow Jones Industrial Average DJIA, -0.43% and the S&P 500 SPX, -0.92% are both down roughly 8% during that same time period.

This story was updated on Jan. 15, 2019.