Swimming pools, hot tubs, and water parks can sometimes harbor germs that survive despite treatment with chlorine.
In a 15-year period, more than 27,000 people in the US have gotten sick and 8 people have died from such germs, according to a report published Thursday by the Centers for Disease Control and Prevention.
In all, there were 493 outbreaks due to germs like Cryptosporidium, Legionella, and Pseudomonas, which can cause diarrhea, skin infections, and lung infections. Hotel pools were responsible for 32% of outbreaks and were the leading location for problems.
People can get sick because of inadequate disinfectant levels in the pool or because the germs are particularly hard to kill even with treatment.
Most of the outbreaks and illnesses were caused by Cryptosporidium, a parasite that is notoriously contagious and difficult to kill with chlorine. Crypto symptoms can include nausea, vomiting, pain, fever, cramps, and diarrhea.
The best way to avoid this particular germ is to not swallow pool water. And please, do not go in the pool if you have diarrhea, or let children with diarrhea swim in a pool.
"We as swimmers and the parents of young swimmers need to remember not to swim when we are sick with diarrhea, and not to let our kids swim when they are sick with diarrhea," Michele Hlavsa, chief of CDC’s Healthy Swimming Program, told BuzzFeed News. "And not to swallow the water."
One more time: DON'T GO IN THE POOL IF YOU HAVE DIARRHEA.
You can also purchase test strips to figure out if a pool has enough chlorine or bromine, which are used to kill germs.
Hlavsa also recommends "doing a mini inspection by yourself, which includes taking a pool test strip and checking the chlorine and bromine level and the pH before you get in."
Such strips cost about $10 for 100 tests and can be purchased at hardware, big box, and pool supply stores, among other places. The strips turn different colors depending on the level of chlorine or bromine in the water, and register pH.
"The pH is important because it's going to determine how effective the chlorine and bromine are at killing germs," Hlavsa said. She noted that saltwater pools also use chlorine to kill germs, it's just generated by running an electrical current through salt water, rather than adding the chemical directly to pool water. "Saltwater pools are chlorine pools," she said.
You can also check the inspection score, often online, for any public pool, whether it's at a hotel, water park, or town pool. They are inspected routinely, just like restaurants, said Hlavsa. "We do it before we go out to eat, we should be doing it before immersing ourselves in water," she said.
"We can’t just assume that the operator has taken care of everything, or our public health department has taken care of everything, we need to take a more active role," she said. "We’ve got to swim healthier and safer."
If you have a lung condition, a weakened immune system, or other risk factors, it's a good idea to avoid being around hot tubs.
While Cryptosporidium cases have not increased since 2007 after rising steadily for a number of years, cases of Legionnaires' disease, which is cased by Legionella bacteria, have increased 14% each year.
Although far less common than crypto, Legionnaires' disease is a dangerous respiratory ailment that occurs when people inhale the bacteria in an aerosol. Six of the eight deaths occurred in Legionella outbreaks.
"Hot tubs have jets that aerosolize the water and if that water is contaminated then you are inhaling potentially Legionella," she said. Talk to your doctor to find out if you are at higher risk from the germ, but people who are older than 50, who smoke, have a chronic condition (particularly a lung condition), or have a weakened immune system due to cancer, a transplant, or other health condition, may be at higher risk.
And if a pool or water park needs to shut down for a while due to a "diarrheal incident," they are trying to keep you safe while they dial up the chlorine levels to kill any potential germs.
"The big issue is Cryptosporidium and Cryptosporidium is very tolerant to chlorine, so once in the pool, it’s very hard to get out of the pool," said Hlavsa. "It can survive for days in a well-chlorinated pool."
You only need to swallow 10 or fewer crypto germs to become infected, and people can release 10 million to 100 million crypto germs in a "diarrheal event," she said.
Also, showering before you get in the pool is a real thing. It's been shown that by showering for at least a minute you are removing the nitrogen-containing dirt and sweat on your body. Nitrogen can combine with chlorine in the pool to make a chemical irritant, which can make your eyes red and irritated.
"It’s actually the chemical irritant that makes our eyes red when we go swimming it’s not the chlorine itself," she said.