Your summer travel schedule has filled up fast. You have that lake house week your family does every July, a weekend in Chicago with your girlfriend, Bonnaroo and—because you're 29—ten weddings on different weekends in disparate parts of the country. That means many nights spent in Marriotts, Wyndhams, and Holiday Inns off interstate exits. The best of these establishments have—in addition to unbruised fruit at the continental breakfast table and full-sized bars of soap —a hot tub. After a day on the road, it feels so good to transplant your ass from a potato chip-grease-stained driver’s seat to a pool of jet-streaming hot water. But can a business that you barely trust to prevent bed bug colonization keep clean and sanitized a basin of hot water into which any highway traveler can enter and soak?

Are Hotel Hot Tubs Full of Bacteria?

By their nature, hot tubs present a bacteria risk that swimming pools—though also chemically treated and shared with strangers—do not. “There are certain types of microorganisms that seem to proliferate in them,” says Aaron Glatt, chair of medicine at South Nassau Communities Hospital and spokesperson for the Infectious Disease Society of America.

Warm water opens the pores of the body. The dirt, oil, and microscopic particles lurking within come out and could pass into the open pores of the other bathers. “It can lead to a lot of superficial skin infections,” Glatt says. “You don’t really see that in colder water.” This is one reason, Glatt adds, people really should shower before getting in the hot tub. It flushes out the pores.

Hot tubs are frequent transfer stations for bacteria. Pseudomonas aeruginosa, a common bacterial infection, is so strongly associated with tubs their main symptom has been dubbed “hot tub rash.” Those afflicted experience inflammation, itching, and pus-filled blisters around hair follicles, particularly on areas of the body that were covered by a swimsuit and hence absorb a lot of hot tub water.

Hot tubs also make for a greater maintenance challenge than pools. “The warm water increases bacteria and uses up chlorine quicker,” says Michele Hlavsa, an epidemiologist and head of the Centers for Disease Control and Prevention’s Healthy Swimming and Cryptosporidiosis program.

Also, the steam from a hot tub stream creates an additional mode by which bacteria spreads, Hlavsa says. The gross stuff can be breathed in through the mouth and nose. Given all that, you might be thinking: Why haven’t these microorganism hellmouths been banned?

How Clean Are Hotel Hot Tubs?

First, it's possible to maintain a clean hot tub that minimizes risk. “Hot tubs can be really clean, as long as you understand you need to pay more attention to them,” says Karen Port, owner of Mirage Spa and Recreation in St. Louis. She recommends owners use both chlorine, a tried and trusted sanitizer, and bromate, a chemical that dissolves more slowly and makes up for the speed at which hot water negates chlorine.

Don’t think Port is shilling for hotel hot tubs because she's in the industry. On the contrary, she says she wouldn’t get in one. Hotel managers “know a lot about the pool, but they don’t know a lot about the hot tub,” Port says, and many tubs at hotels, in her estimation, don’t get the attention they require.

Hlavsa says that many hotel tubs are well kept and generally safe. “It really depends on the hot tub,” she says, and there are readily available tools that can help one decide whether or not to enter a particular tub.

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One is a search engine: Local health departments often test the water of public pools and hot tubs and post inspection reports online. “They are done on the local level, by the county or the city or the state,” Hlavsa says. “There may be a letter or a number score or a full report that would tell you about [health code] violations.” In any case, thanks to modern technology, your friend should be able to see if the tub or the hotel housing it have a problematic history—even if he’s just breezing into town and doesn’t know about the Weird Butt Rash Outbreak of ’14.

Another tool is a pool test strip. These test the chlorine, bromine, and/or pH level of pool of water. For hot tubs, the CDC recommends a pH level of 7.2 to 7.8, free chlorine concentration of at least three parts per million, and free bromine concentration of at least four ppm. “A hundred strips costs $10,” Hlavsa says, “and you can get them at any big box [department], pool supply or hardware store.” And of course, do a visual inspection, she says. Don’t enter a hot tub that looks cloudy or dirty.

How Sick Can You Get from a Hotel Hot Tub?

From 2000 to 2014, there were 493 infectious disease outbreaks linked to chemically treated recreational water sources, i.e. pools and hot tubs, in the United States, according to a CDC report. (An outbreak was defined as two or more people getting the same disease from the same pool.) These incidences caused at least 27,219 illnesses and eight deaths.

A third of the outbreaks occurred at hotels, the most common type of site in the data, and 65 hotel-related outbreaks were associated with hot tubs. Among the 363 outbreaks with a confirmed infectious etiology, most (58 percent) were cryptosporidium, a diarrheal disease caused by microscopic parasites. Although cryptosporidium was the infectious disease at play in 58 percent of the outbreaks, those outbreaks spread further, so it was the cause of 89 percent of the illnesses in the report, affecting 21,766 people.

It’s easy to imagine how the parasites got in the water—though you’d probably rather not. Warm water “tends to make people loosen up,” says Hlavsa, who was the lead author of the report. Fluid leaks out of people with diarrhea, from you know where, and their parasites are absorbed by other bathers, often (brace yourself) through the mouth, she says. “Don’t even consider getting in the water if you have diarrhea,” Hlavsa says. This is another reason one should never swallow the water of pools and hot tubs.

Sixteen percent of the outbreaks and three percent of the illnesses were the result of legionella, a germ that causes Legionnaires’ disease, a severe respiratory disease. Out of the eight deaths recorded in the report, Hlavsa says, six were confirmed cases of Legionnaire’s and the other two were suspected.

While these cases were serious, they are rare compared to other kinds of diseases and deaths. Over 15 years, infectious diseases from all non-natural reactional water pools—of which hot tubs were one small subsection—caused 27,219 illnesses and eight deaths. In comparison according to the CDC, foodborne disease causes 48 million illnesses, 128,000 hospitalizations, and 3,000 deaths per year. A hot tub is a relatively rare starting point for an illness in America.

What Kind of Bacteria Is in a Hotel Hot Tub?

Most bacteria that fester in hot tubs are common types and the average human body can withstand them. “I would only say don’t get in the hot tub if you have an immunodeficiency,” Glatt says. This advice extends to people who have recently undergone chemotherapy or have one of a handful of medical conditions that weaken the immune system. Also those with easy bacterial entry points, like open wounds or new tattoos, should abstain, Glatt says. For most people, there probably isn’t anything frothing around an average hot tub that their body can’t defeat.

In that sense, hotel hot tubs are a little like ATM keypads or cell phone surfaces: It’s best not to think about the germ accumulation inherent to their existence, if you’re inevitably going to use one, and it’s sorta okay not to think about it, because rarely do they cause serious illnesses. Hotel hot tubs are great places for bacteria to fester, but most of those germs can be defeated by a healthy immune system. Outbreaks of serious diseases are rare. If, after a long day of riding the interstate, you want to indulge in the hot tub of your mid-range motor inn, it probably won’t hurt you. And, to be sure, you can use local inspection reports and inexpensive test strips to determine if this particular Radisson is falling down on its hot tub maintenance duties.