Hot tubs can cause respiratory illness when contaminated water is turned into mist or aerosols and then breathed into the lungs. One of the most important concerns is Legionella, a type of bacteria that can cause Legionnaires' disease or the milder illness known as Pontiac fever.
If you develop cough, shortness of breath, fever, muscle aches, or other respiratory symptoms after using a hot tub, especially within the following two weeks, contact a healthcare provider and tell them about the recent hot tub exposure.
1. Understand How A Hot Tub Can Affect Your Lungs
Hot tubs create large amounts of mist and tiny airborne water droplets. If the water contains harmful microorganisms, those droplets can be inhaled instead of simply contacting the skin.
- Jets and aeration create fine water droplets that can be breathed in.
- Contaminated water can expose users through inhalation even if they never swallow the water.
- Indoor hot tubs may concentrate mist in enclosed areas if ventilation is poor.
- Poorly maintained water increases the risk that disease-causing organisms can grow.
Solution: Do not use a hot tub that appears poorly maintained, has cloudy or slimy water, or cannot be verified as properly sanitized.
2. Know What Legionella Is
Legionella is a type of bacteria that can grow in human-made water systems, including hot tubs. When contaminated water is aerosolized, people can become exposed by breathing in the mist.
- Legionella can grow in hot tubs when conditions allow the bacteria to multiply.
- Warm water can provide favorable conditions for bacterial growth.
- Low disinfectant levels increase the risk of uncontrolled bacterial growth.
- Biofilm and sediment can provide additional environments where bacteria persist.
Solution: Proper sanitation, water balance, filtration, cleaning, and circulation are essential for reducing the risk of Legionella and other waterborne organisms.
3. Understand Legionnaires' Disease
Legionnaires' disease is a serious type of pneumonia caused by Legionella bacteria. It can require hospitalization and should not be confused with a simple cold or mild irritation from spa chemicals.
- Cough is a common symptom.
- Fever may develop.
- Shortness of breath can occur as the illness affects the lungs.
- Muscle aches, headache, chest pain, nausea, diarrhea, or confusion may also occur.
Solution: If you develop respiratory symptoms after recent hot tub exposure, seek medical attention promptly and tell the healthcare provider that you used a hot tub.
4. Know The Difference Between Legionnaires' Disease And Pontiac Fever
Legionella can cause two different illnesses. Legionnaires' disease involves pneumonia, while Pontiac fever is generally a milder illness that does not cause pneumonia.
- Legionnaires' disease is the more serious illness and affects the lungs.
- Pontiac fever is usually milder and self-limiting.
- Both illnesses are caused by Legionella bacteria.
- Symptoms alone may not tell you which illness is present.
Solution: Do not try to diagnose yourself based only on symptoms. A healthcare provider should evaluate significant respiratory illness after hot tub exposure.
5. Pay Attention To Symptoms Within Two Weeks Of Hot Tub Use
Respiratory illness caused by Legionella does not necessarily begin while you are still using the spa. Symptoms can develop later, which is why recent exposure history is important.
- Cough after recent hot tub use should be noted.
- Shortness of breath deserves medical attention.
- Fever or muscle aches may accompany respiratory illness.
- Symptoms within two weeks of hot tub exposure should be mentioned to your healthcare provider.
Solution: CDC advises people who develop symptoms such as cough, shortness of breath, fever, or muscle aches within two weeks of hot tub use to see a healthcare provider right away and report the exposure.
6. Know Who Is At Higher Risk
Anyone can be exposed to contaminated hot tub mist, but certain people are more likely to develop Legionnaires' disease after exposure to Legionella.
- People age 50 or older have increased risk.
- Current or former smokers are at greater risk.
- People with chronic lung disease may be more vulnerable.
- People with weakened immune systems or taking immune-suppressing medications have increased risk.
Solution: People in higher-risk groups should be particularly cautious about using hot tubs when the sanitation or maintenance history is uncertain.
7. Check The Chlorine Or Bromine Level
Proper disinfectant levels are one of the most important defenses against bacterial growth in a hot tub. High water temperature and heavy bather loads can consume disinfectant rapidly.
- Low sanitizer can allow bacteria to multiply.
- Heavy use can reduce sanitizer levels quickly.
- Body oils and organic contaminants increase sanitizer demand.
- A zero sanitizer reading is a strong reason not to use the spa.
Solution: Test the sanitizer regularly and correct low levels before using the hot tub. Maintain the disinfectant and pH ranges recommended for your spa and chemical system.
8. Check The pH And Overall Water Balance
Sanitizer cannot be evaluated separately from pH. Improper pH can reduce disinfectant effectiveness and contribute to poor overall water quality.
- High pH can reduce chlorine effectiveness.
- Low pH can create corrosive water conditions.
- Incorrect alkalinity can make pH unstable.
- Poor water balance can make sanitation problems harder to control.
Solution: Test pH and alkalinity along with the sanitizer and correct the overall water balance before returning the spa to normal use.
9. Do Not Ignore Cloudy Water Or Slimy Surfaces
Visible water-quality problems can indicate that a spa is not being maintained properly. Cloudiness, slime, unusual odor, or persistent foam should be treated as warning signs rather than cosmetic problems.
- Cloudy water can indicate poor sanitation or filtration.
- Slimy surfaces may indicate biofilm or organic buildup.
- Persistent foam can indicate excessive contaminants.
- Unusual odor can indicate deteriorating water quality.
Solution: Stay out when obvious water-quality warning signs are present. See our Is Cloudy Hot Tub Water Safe?, Slimy Hot Tub Water, and Hot Tub Water Smells Bad guides for additional troubleshooting.
10. Understand Why Biofilm Matters
Biofilm can develop on wet surfaces inside hot tub plumbing and equipment. It can provide an environment where microorganisms persist and can make sanitation more difficult.
- Biofilm can exist inside plumbing where it cannot be seen.
- Sediment and organic buildup can support bacterial growth.
- Repeated sanitizer loss may indicate hidden contamination.
- Slimy debris from jets can be a warning sign of plumbing buildup.
Solution: If sanitation problems repeatedly return, consider whether the plumbing requires an appropriate purge and deep cleaning rather than repeatedly treating only the visible water.
11. Inspect The Filter And Circulation System
Water sanitation depends on circulation and filtration working properly. A spa with stagnant areas, restricted flow, or dirty filters may be more difficult to keep sanitary.
- Dirty filters can trap organic material and reduce flow.
- Poor circulation can interfere with disinfectant distribution.
- Short filtration cycles may allow water quality to deteriorate.
- Pump or flow problems can reduce filtration effectiveness.
Solution: Clean or replace dirty filters and verify that the circulation system is operating correctly. Water-treatment chemicals cannot compensate for equipment that is not moving and filtering the water properly.
12. Be Extra Careful With Indoor Hot Tubs
Hot tubs generate large amounts of humidity and aerosolized water. In an indoor environment, poor ventilation can allow mist and humidity to accumulate around the spa.
- Indoor spaces can hold aerosolized moisture longer than open outdoor areas.
- Poor ventilation can create uncomfortable or humid conditions.
- Jets and blowers can generate significant mist.
- Good ventilation is important for both comfort and air quality.
Solution: Maintain appropriate ventilation around indoor spas and address persistent condensation, excessive humidity, or poor air circulation. Proper air handling does not replace proper water sanitation.
13. Take Extra Care With Hotel And Vacation Rental Hot Tubs
Hotels, resorts, gyms, cruise ships, vacation rentals, and other shared spas may experience far heavier bather loads than a residential hot tub. Users also may have little knowledge of the maintenance history.
- High bather loads can rapidly consume sanitizer.
- Unknown maintenance history makes the water condition harder to judge.
- Cloudy or slimy water is a strong warning sign.
- People at higher risk for Legionnaires' disease should be especially cautious.
Solution: Inspect shared spas carefully before entering and use test strips when appropriate. If the water is cloudy, surfaces are slimy, or sanitation cannot be verified, stay out and report the condition to the operator.
14. Know When To Seek Medical Attention
Respiratory symptoms after hot tub exposure should not automatically be dismissed as a cold, allergies, or irritation from steam. Recent exposure can be important information for a healthcare provider.
- Cough after recent hot tub exposure deserves attention.
- Shortness of breath should be evaluated promptly.
- Fever or muscle aches can occur with Legionella illness.
- People in higher-risk groups should have a particularly low threshold for contacting a healthcare provider.
Solution: If you used a hot tub within the last two weeks and develop cough, shortness of breath, fever, muscle aches, or other significant respiratory symptoms, contact a healthcare provider right away and specifically mention the hot tub exposure.
Key Takeaways
- Hot tubs can expose users to respiratory germs through mist and aerosols from contaminated water.
- Legionella can cause Legionnaires' disease, a serious type of pneumonia, and Pontiac fever, a milder illness without pneumonia.
- Cough, shortness of breath, fever, and muscle aches after recent hot tub use should be taken seriously.
- People age 50 or older, current or former smokers, and people with chronic lung disease or weakened immune systems have increased risk.
- Proper sanitizer, pH, filtration, circulation, and plumbing cleanliness help reduce the risk of Legionella growth.
- Tell your healthcare provider about recent hot tub exposure if respiratory symptoms develop.
If a hot tub is cloudy, slimy, poorly maintained, or cannot be verified as properly sanitized, stay out. Good water chemistry, clean filters, adequate circulation, and regular cleaning are important not only for how the water looks but also for reducing exposure to organisms that can cause respiratory illness.
Most importantly, if you used a hot tub within the last two weeks and develop cough, shortness of breath, fever, muscle aches, or other significant respiratory symptoms, contact a healthcare provider and make sure they know about the recent hot tub exposure.