Do you have a cruise planned or are you thinking of booking one? They’re a great, relaxing, don’t-worry-about-a-thing type of vacation that millions of Americans love. And with about 30 embarkation points across the nation, chances are one is within easy reach. At most, a cruise port is probably only a short flight away.

Generally, a cruise is a very safe vacation and free from illness, but there are steps you can take to lessen the odds that you will be struck down by a stray bug or have an accident.

First, try to wind down a couple of days before your cruise. “Leisure sickness” occurs when the transition from the stress of work to relaxation is fast — as in leaving work one day and boarding a plane the next. If you were scurrying around finishing projects, the stress hormones that helped you meet your deadlines and also fight off illnesses, suddenly fade away as another hormone, cortisol, steps in to ease the stress. Unfortunately, cortisol lowers your immunity as it calms, and suddenly you come down with a terrible cold or a migraine headache.

Cruise personnel work hard to keep ships sparkling clean, but they can’t control everything. Although each passenger is asked health questions, such as “Do you have a fever?” it’s easy for someone with a virus to board — some aren’t even aware they’re sick.

Cruise ships by their nature include large groups of people in confined spaces, providing ideal conditions for flu, colds, and gastrointestinal illnesses to spread.

The norovirus has a particularly nasty reputation among cruisers. Every year, it sickens up to 21 million people, according to the Centers for Disease Control, but the fact is that fewer than 1 percent of cases occur on cruise ships. However, if a sick person boards a ship, the virus can quickly spread. Your best defense against norovirus as well as the common cold is to avoid touching spots that might harbor the virus, like elevator buttons and ship rails, and wash your hands frequently.

Even though your cabin may appear spotless, bring hand sanitizer or antibacterial wipes to clean the TV remote control, light switches, and door knobs as soon as you enter — all have been shown to harbor bacteria, just like in hotel rooms.

Motion sickness isn’t the problem that it used to be due to stabilizers on modern ships and the ability to navigate around storms. But if you tend to have motion sickness, you might ask your doctor to prescribe Transderm Scop, a transparent scopolamine patch applied behind the ear which is effective for up to three days. Over-the-counter solutions include Dramamine and Bonine.

Ginger quells queasy stomachs for many people, and some cruisers use a Sea-Band wristband, which applies acupuncture to sensitive points to ease queasiness.

Trips and falls are more common on ships than on land. Decks may be slippery from water, raised doorsills are common, and going down stairs while the ship is in motion can result in a nasty fall. Watch where you step, and use a handrail when taking the stairs.

While your ship may be clean, the ports of call can be dicey. Traveler’s diarrhea (TD) is the single most common illness contracted by people on vacation, and it can be caused by food contaminated with e. coli bacteria or noroviruses. It can also be caused by contaminated water, including ice. While in port, avoid drinks with ice and any uncooked fruits or vegetables. Wash your hands frequently, and carry a mini-bottle of hand sanitizer with you.

Carry sun tan lotion to avoid sunburn and bug spray to protect you from disease-carrying insects, including mosquitoes that carry the Zika virus.

Back on board, you might want to skip the hot tub. Several passengers in recent years have sued cruise lines for being negligent and allowing dangerous bacteria in their hot tubs. Lawsuits have claimed hot tubs tested positive for methicillian-resistant staphylococcus aureus (MRSA) and Legionella bacteria. Hot tubs, in general, are often found to contain coliform and enterococcus — fecal bacteria. Just say no.

While lavish all-you-can-eat buffets are tempting, don’t overindulge — at least not too much. Consumer Reports says that given the rich food and amount of alcohol available on cruises, they put passengers in the same category of high risk for sudden cardiac deaths as major holidays like Thanksgiving and Christmas. Your cruise director won’t want to admit it, but most ships have a morgue.

It’s easier to limit food portions if you stick to eating in the dining room. In addition, you also avoid the risk of picking up germs from serving utensils used by dozens of other cruisers at the buffet.

Also, the sea air might not be as pure as you would expect. A German study found that the pollutants coming from a ship’s exhaust could mean that passengers inhale up to 60 times higher concentrations of pollutants than they would in natural settings. Lessen your risk by not staying on deck for long periods, and if you’re really concerned — or have asthma or other lung problems — you might consider packing a portable air purifier to use in your cabin.