Microbial Infections Associated with Whirlpool Baths and Spas
Kelly A. Reynolds, Ph.D.
Numerous disease outbreaks have
been associated with whirlpool baths and spas throughout the world.
Typically, whirlpool baths are drained and cleaned between each
use. Because of their therapeutic benefits, they are commonly
used in hospitals and therapy units and often by immunocompromised
persons, who are more susceptible to microbial infections. Spas,
on the other hand, may be repeatedly used by multiple bathers
and continually treated.
persons bathing in whirlpools and spas are capable of contaminating
the water with just about any enteric pathogen (spread by the
fecal/oral route), the primary microbial disease causing agents,
associated with hot tubs, are the opportunisticcapable of
infecting hosts with compromised immunitypathogens, Legionella
and Psuedomonas. These bacteria are naturally present,
capable of survival in water systems, and able to proliferate
under warm, moist conditions.
Routes of microbial
infection from hot tubs may be either via aerosol mists, direct
ingestion of the water or skin contact. The oral exposure route
is minimized, relative to other forms of recreational swimming,
due to the fact that submersion of the head under water is not
routinely practiced. Still, the aerosol route may be increased
due to the use of mist-producing jets for water circulation and
found in whirlpools and spas
Legionella is the causative agent of Legionnaires'
disease and Pontiac fever. Both syndromes are characterized initially
by anorexia (lack of appetite), malaise (a general feeling of
discomfort), myalgia (inflammation and tenderness of the muscles)
and headache. Within 24 hours a fever and chills ensue. A nonproductive
cough may occur and abdominal pain and diarrhea are seen with
many patients. Respiratory failure is also possible, with a 15
percent fatality rate in hospitalized cases. Pontiac fever most
commonly occurs in healthy persons and is a much milder form of
the disease with no pneumonia or death. The infection is self-limiting
in 2-5 days.
Over 28 species
of Legionella cause disease, with L. pneumophila
being the most prominent pathogen of the group. The disease is
found worldwide with most cases in the summer and fall months.
Legionella may be present in high numbers in waters as
hot as 40°C (105°F). Hot water systems, air-conditioning
cooling towers, and evaporative condensers have all been implicated
in outbreaks, as have decorative fountains and retail store misters.
The organism has been isolated from creeks, ponds and soils. Transmission
is thought to be via aerosol inhalation. Studies show that 1-to-20
percent of the general population have been exposed, according
to serological studies.
are frequently isolated from moist environments and soil and cause
significant illnesses, including pneumonia, urinary tract infections,
and surgical and burn wound infections. Typically an opportunistic
pathogen, persons at greatest risk in the community are those
that have cystic fibrosis where lung infections are often fatal.
While most infections are nosocomial (acquired in a hospital),
milder forms of disease including swimmer's ear and skin infections
are frequently associated with recreational water breaks. Corneal
infections and urinary tract infections have been documented following
exposure to whirlpool baths and spas. Vision loss due to pseudomonal
keratitis could occur rapidly (24-48 hours) if proper treatment
is not initiated. ignored.
A survey of 17 whirlpool
baths in from 16 nursing homes in two health districts in the
U.S. showed that Pseudomonas aeruginosa was present in
all after agitation. Although resultant infection was rare (only
one of 253 exposed), the nursing home inspection unit advised
that only continent residents with intact skin be allowed to use
the bath.1 During 1991-1992 the CDC reported
that, of the 34 outbreaks associated with recreational waters
in 21 states, Pseudomonas dermatitis from hot tubs or whirlpools
was the most commonly identified etiological agent with 12 outbreaks.2 Another survey of whirlpools
found Legionella in nearly 66 percent of the 32 samples collected.3
Concern is mounting
over the potential presence of disinfectant resistant microbes
in recreational waters. Hepatitis A and Norwalk virus are known
to survive free chlorine concentrations of 1 mg/L (1 ppm) at pH
7.5 and 25oC (77oF) for up to 16 minutes. Cryptosporidium
has also been shown to survive the above listed conditions for
more than six days,4 allowing ample time for transmission
to swimmers. Infections from Cryptosporidium are usually
self-limiting in healthy individuals but may cause severe diarrhea
and vomiting, and require hospitalization for supportive therapy
(treatment is unavailable). Infections may be life threatening
in immunocompromised persons. Although there has been a Cryptosporidium
outbreak from a recreational water fountain and many outbreaks
associated with swimming pools, no outbreak has been associated
with whirlpools or spas to date.
At neutral pH, free chlorine kills most bacteria in minutes. However,
many bacterial species are constantly being reintroduced, from
users or the environment, to spa units, requiring diligent maintenance
of proper disinfectant concentrations. The bacteria may come from
various sources such as the hoses and plumbing used to fill the
pools or biofilms in the filtration and jet systems in the pool.
Even if proper disinfectant concentrations are kept, conditions
of protective biofilm growth or the presence of resistant organisms
may still be a problem.
Few studies have
been conducted to evaluate the effectiveness of disinfectants
on pathogen inactivation under typical conditions of hot tub use.
Higher temperatures characteristic of hot tubs may decrease inactivation
times of pathogens, but may also aid in the increased reduction
of chlorine residuals due to evaporation. One study found that
Cryptosporidium survived concentrations of 2 mg/L of free
chlorine at 30oC (86oF) for up to 72 hours.5
The best method
for maintaining a safe spa is to clean and disinfect with hypochlorite
after each use. Although chlorine treatment is highly effective
against bacteria, concentration levels must be maintained. One
outbreak of follicular rash among 20 persons occurred when levels
of free chlorine fell to 0.1 mg/L compared to the acceptable level
of 0.9-1.2 mg/L, where no cases were reported.6 Others have found that levels of 3.0 mg/L of
chlorine or 6.0 mg/L of bromine were necessary to prevent rapid
regrowth of the bacteria.7 In
addition, the time spent swimming or bathing correlates positively
with disease incidence. The risk of acquiring Legionnaires'
disease increases by 64 percent for every hour spent in the
spa water.8 Persons gathered around the spa,
but not immersed in the water, are also more likely to contract
A recent study evaluated
the use of ozone, bromine, enzyme, and chlorine sanitizers to
inactivate bacteria in spas.9 The
researchers used the Standard Protocol 50 set by the National
Sanitation Foundation (NSF), which requires a 3-log reduction
of Enterococcus hirae and a 6-log reduction of Pseudomonas
aeruginosa within 30 minutes. Conditions of the tub included
a temperature of 104oF and the addition of baby oil and urea,
to simulate bather use. The study found that ozone and an enzymatic
sanitizer were not effective at reducing the number of bacteria
when used as per manufacturer instructions. Bromine was effective,
reducing E. hirae by the desired orders of magnitude within
two minutes and P. aeruginosa within three. Chlorine was
used as the control treatment and was the most effective agent.
Proper and consistent maintenance of effective disinfectant levels
is crucial to ensure the safety of recreational and therapeutic
spas. Severely immunocompromised individuals (HIV infected, transplant
recipients, etc.) are advised not to swim in water that is likely
to be contaminated, and to avoid swallowing water while bathing
in recreational water.4
1. Hollyoak, V.,
et al., Whirlpool baths in nursing homes: use, maintenance,
and contamination with Pseudomonas aeruginosa. Communicable
Disease Report CDR Review, 1995. 5(7): p. R102-4.
2. Moore, A.C., et al., Surveillance for waterborne disease
outbreaks--United States, 1991-1992. Morbidity Mortality Weekly
Report Centers for Disease Control Surveillance Summary, 1993.
42(5): p. 1-22.
3. Kuroki, T., et al., Occurrence of free-living amoebae and
Legionella in whirlpool bathes. Kansenshogaku Zasshi, 1998.
72(10): p. 1056-63.
4. CDC, Swimming pools/recreational waters. May 22, 2000.
5. Carpenter, C. et al. Chlorine disinfection of recreational
water for Cryptosporidium parvum. Emerging Infectious Diseases.
1999. 5: 579-84.
6. Lindberg, A., et al., Pseudomonas infection associated with
whirlpool bath. Ugeskrift for Laeger, 1992. 154(49): p. 3507-9.
7. Price, D. and D.G. Ahearn, Incidence and persistence of
Pseudomonas aeruginosa in whirlpools. Journal of Clinical
Microbiology, 1998. 26(9): p. 1650-4.
8. Jernigan, D.B., et al., Outbreak of Legionnaires' disease
among cruise ship passengers exposed to a contaminated whirlpool
spa. Lancet, 1996. 347(9000): p. 494-9.
9. Watt, P.M., et al. Evaluation of the performance of non-chlorine
spa sanitizers in 100th General Meeting of the American Society
for Microbiology. 2000. Los Angeles, Calif.: ASM. Abstract