Could Legionnaires' Disease be lurking in your Hot Tub?

by Peter Gunn, on 27-11-2019
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Richards Hot Tub

I confess – despite an acute awareness of the potential dangers of hot tubs and other similar spa facilities combined with a long held professional belief that caution is the order of the day – I’m continually drawn to the idea of embracing what seems to be a great environment for relaxation. 

This may well also be associated with a rather enjoyable family visit to Spa, a town in Belgium, somewhere within the Liège province . It’s home to a resort with famous medicinal mineral springs and the name of the place has obviously evolved to become a noun denoting any such similar place. Nowadays, the word “spa” is commonly used to refer to resort areas with mineral springs, health spas providing therapeutic baths, fashionable hotels, or even simply a hot tub for relaxation.

I’d also highlight despite my cynicism, many of the qualities that hot tub and spa manufacturers continue to peddle consistently, do have some merit – not only superficially but also in providing physical and mental stimulus!


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The message of the water hygiene professional however, is rather more mundane, one of cleaning routines and maintenance tasks, disinfection and, God forbid, record keeping. This is perhaps a clue to the imbalance in the ever increasing installation and use of ‘hot tubs’ and the potential for irregular or ad hoc implementation of maintenance regimes.


What is a hot tub anyway?

These days a hot tub tends to be more than a wooden-staved barrel filled with warm water and colloquially the term hot tub is now commonly used to describe a variety of ‘jetted baths’.

The Health & Safety Executive’s HSG282 The control of legionella and other infectious agents in spa-pool systems described such facilities as ‘…a self-contained factory-built unit for indoor or outdoor use and is designed for sitting in. They are typically filled with treated water, maintained at a temperature above 30 °C, fitted with air jets and aerated. They are generally designed for a small number of discrete bathers where the water is not changed, drained or cleaned after every use. Hot tubs are not for swimming in and do not have a balance tank. These are likely to be small units but with regular daily usage and the above factors, along with the turnover of water, must be considered as part of the risk assessment’.


So… to the title of this blog “What is lurking in your ‘hot tub’?” and a notable reminder which came to press in September 2019:

In the US at the North Carolina Mountain State Fair 141 cases and four deaths from Legionnaires' disease were reported along with further cases of Pontiac fever confirmed from the same source.

In short, microbiological hazards can and are frequently found in hot tubs. Water in hot tubs should be free from irritant substances, chemicals and infectious microbiological agents at levels which may be harmful to health.


The Facilitator

Biofilm is a complex association of micro-organisms which can adhere to hot tub surfaces, particularly in the associated plumbing systems, where it can be difficult to remove. Biofilms in hot tubs can and often do lead to cloudy water, odours, scale build-up on the heater and corrosion of the heater, pumps, filtration system and jets. The risk of microbial growth increases with the introduction of nutrients such as mucus, saliva, perspiration, dead skin, suntan lotion, spray tans, cosmetics, shampoo and soap residues, urine, faecal matter and hair. These nutrients can be used as building blocks by the microorganisms in biofilm as they establish colonies in low flow areas of hot tubs or spa-pools.

Crucially, poorly designed or poorly managed spa-pool systems can provide the conditions to create the risk of acquiring an infectious disease.


The Hazards

HSG282 very clearly highlights the various microbiological hazards that are ‘commonly’ associated with hot tubs:

Legionella species Legionellosis is a collective term for diseases caused by the legionella organism including the most serious Legionnaires’ disease, as well as the similar but less serious condition of Pontiac fever. There have been a number of outbreaks linked to spa pools, including those in leisure centres, hotels, holiday homes, cruise ships and those on display. Everyone is susceptible to infection but there is a heightened risk with:

  • increasing age, particularly those over 45;
  • smokers and heavy drinkers;
  • those with existing respiratory diseases or certain illnesses and conditions such as cancer, diabetes, heart and kidney disease;
  • those with an impaired immune system.’

Coliforms and Escherichia coli –‘The presence of E.coli in spa-pool water is an indication that faecal material has either entered the water from contaminated skin, or has been accidentally or deliberately introduced. Coliforms occur on vegetation and in soil as well as faeces, so their presence alone indicates external contamination. The presence of coliforms and/or E.coli also confirms that the treatment has failed to control this contamination.’


Pseudomonas aeruginosaNumerous outbreaks of folliculitis caused by P.aeruginosa are associated with spa pools and hot tubs. Folliculitis presents as a red rash caused by infection of the hair follicles, usually about 48 hours (range 8 hours–5 days) after immersion in pool water, and is related to the duration of immersion as well as the degree of contamination of the water. Children are generally more susceptible than adults.’


Mycobacterium avium and Mycobacterium speciesRespiratory disease has been associated with non-tuberculous mycobacteria, particularly Mycobacterium avium, in association with spa pools and hot tubs.’


Other potential infections – ‘Other infections such as amoebal, parasitic and other gastrointestinal infections, furunculosis (caused by Staphylococcus aureus) and Molluscum contagiosum (a viral skin infection producing papillomas) have also been associated with using spa pools.’


Guidance and Management

The Health & Safety at Work etc. Act 1974 [HSWA] does not apply to the private owners of spa pools or hot tubs or where there is no financial gain and they are for the exclusive use of the owner, family and occasional guests. That said to ensure its safe use, the spa pool or hot tub should be used and maintained in accordance with the manufacturers’ instructions.

However, domestic type and commercial spa pools or hot tubs used as part of a business activity are certainly subject to the general duties under the HSWA. Within commercial settings, there is a higher number of users than for domestic-type spa pools and the number of bathers cannot be clearly anticipated or recorded. There is a legal requirement for these systems to be managed and controlled in proportion to the risk and the water hygiene risk assessment should consider the type of system/pool and its use.


Lessons Learnt

The British and Irish Spa and Hot Tub Association some years ago delivered an article on lessons learnt post the announcement of the £1-milion fine for JTF Warehouse, following the death of two people from Legionnaires’ disease and a further 20 people contracting the disease, citing this as ‘a landmark moment for the hot tub industry in the UK’ and that ‘every reputable hot tub company is aware that these deaths were completely avoidable had JTF Warehouse put in place a robust water hygiene management regime’.

What to do next?

The HSE’s HSG282 provides excellent guidance on minimising risks whilst using hot tubs and similar equipment. The guidance is based on the key principles of the COSHH Regulations ‘which provides a framework of duties designed to assess, prevent or control the risks from hazardous substances, including chemicals and biological agents such as legionella and other infectious agents, and take suitable precautions.

The essential elements are:

  • Water Hygiene risk assessment;
  • prevent exposure or substitute with a less hazardous substance or process/method, where reasonably practicable;
  • control exposure if prevention or substitution are not reasonably practicable;
  • maintain, examine and test the control measures;
  • provide information, instruction and training for their employees;
  • provide health surveillance of employees, where appropriate.’


If you have questions regarding the issues raised above or you would like to speak with one of our consultants please click here to get in touch.

Editors Note: The information provided in this blog is correct at date of original publication - November 2019.

© Water Hygiene Centre 2019


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About the author

Peter Gunn

Peter has been acting as an AE [water] and providing competent help services to multiple public sector and public services client in both the Midlands and North of England since 2004, and working within Legionellosis risk management since 1997. Peter currently acts as AE [water] for 11 large public services client’s including University’s, Councils, Healthcare and Constabularies.

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