Explainers

Legionnaires’ Disease – What is it and What do You Need to Know?


‘Suspected outbreak’.

Two words that every medical professional hates hearing when they listen to the news.

The most recent outbreak was caused by Legionnaires’ disease in Melbourne (April 2017) where five patients were treated – all between the ages of 51 and 71 (ABC 2017).

So what is Legionnaires’ disease?

A form of atypical pneumonia, Legionnaires’ disease is caused by any type of Legionella bacteria. Symptoms include cough, shortness of breath, muscle pains, headaches, high fever – with nausea, vomiting and diarrhoea also common. Symptoms often appear 2 to 10 days after exposure to the bacteria.

The disease is named after the outbreak where it was first identified – at the 1976 American Legion convention in Philadelphia. Within a week of the three-day convention ending, more than 130 people had been hospitalised by Legionnaires’ disease with 25 deaths (Time 1976).

An investigation was carried out by the US Center for Disease Control and Prevention, who eventually established that the Legionella bacterium was to blame – it had been breeding in the cooling tower of the hotel’s air conditioning system and spread throughout the building.

So what caused the Legionnaires’ outbreak in Melbourne?

Just like the 1976 outbreak in Philadelphia, cooling towers are thought to be to blame for the disease in Melbourne. 3 workplaces and 89 cooling towers within the Melbourne central business district were disinfected – the authorities took no delay in trying to contain the outbreak.

“Five cases of Legionnaires’ disease is an unusual number of cases of Legionnaires’ disease in Victoria in a short space of time and it’s very concerning,” Dr Romanes, Deputy Chief Health Officer said.

Legionnaires’ disease is usually spread by breathing in mist containing the Legionella bacteria or by aspirating contaminated water. Typically, it doesn’t spread directly between people and most people who are exposed don’t become infected. Risk factors for infection include:

  • Older age
  • History of smoking
  • Chronic lung disease
  • Poor immune function
  • People on immune suppression medication

The Legionella bacteria can also cause Pontiac fever. Unlike Legionnaires’ disease, Pontiac fever affects the young and healthy with an infection that remains in the upper respiratory system rather than affecting the lungs. It is non-fatal and has a much shorter incubation and duration than the much more serious Legionnaires’ disease.

So what do health professionals need to know about Legionnaires’ disease?

Sporadic and epidemic forms of Legionnaires’ disease do occur in Australia – with Legionella infections believed to account for 5-15 per cent of community-acquired pneumonias (Victoria State Government 2017). There is no vaccine and prevention depends on good maintenance of water systems, outbreaks in Australia are generally associated with manufactured water systems rather than contaminated warm water systems.

The majority of cases require hospitalisation, with a fatality rate of approximately 10% (CDC, 2016). Early antibiotic treatment is essential for improving survival rates – recommended agents include fluoroquinolones, azithromycin and doxycycline.

Legionnaires’ disease can be hospital-acquired – so what does that mean for health professionals?

It is possible for an outbreak of Legionnaires’ to originate from a hospital. Known as nosocomial pneumonia but familiarly called hospital-acquired Legionnaires’ disease.

Risk factors for nosocomial pneumonia are:

  • Recent surgery
  • Intubation and mechanical ventilation
  • Aspiration
  • Use of respiratory therapy equipment

Patients suffering from Legionnaires’ disease are significantly more likely to have undergone endotracheal tube placement, or have been intubated for longer than patients with other types of pneumonia (Kool et al., 1998).

Those most susceptible to Legionnaires’ disease are immunocompromised patients including solid-organ transplant recipients and those receiving corticosteroid treatments (Strebel et al. 1988). Heart transplant patients have been shown to have a high incidence of the disease, for example, whereas patients receiving a bone marrow transplant have a lower risk.

As the symptoms of Legionnaires’ disease are the same as any infection – high fever, nausea, etc; it is crucial that the medical team consider the disease as a possible cause. This is particularly the case for post-operative patients where wound infection is often considered long before any other potential diagnosis.

Being acquainted with the protocol and procedures for hospital-acquired Legionnaires’ disease should be a priority for all nursing staff.

Hospital-acquired cases tend to make up a small proportion of all reported cases of Legionnaires’ disease, however, the fatality rate tends to be much higher than infections acquired within the community.

Originally, it was thought that cooling towers were the main source of hospital-acquired Legionnaires’ disease, reinforced by the largest outbreak of 449 cases being associated with the air-conditioning cooling towers of a Spanish city hospital (Garcia Fulgueiras et al. 2002). However, many cases of nosocomial have actually been associated with piped hot and cold-water distribution systems.

Whilst the management of water systems within a hospital is down to the premises staff, there are precautions that nurses and midwives can take to prevent the spread of Legionella infections.

Water used to rinse and clean respiratory apparatus should always be sterile – this includes usage for seemingly low risk items such as the machines themselves.

Birthing pool water is a potential source of the infection and so they should be physically cleaned and disinfected before and after use. Any hoses used for filling the pool should also be thoroughly taken apart and disinfected. Where birthing pools are only used intermittently, disposable pool liners’ should also be added as an additional precaution.

Whilst outbreaks of Legionnaires’ disease are relatively rare – in 2014, there were 424 notifications of Legionellosis in Australia, representing a rate of 1.8 per 100,000 (Department of Health 2016), it is important to remain vigilant and take all necessary precautions. An awareness of water system usage within the care environment is essential not only for management, but for medical staff too.

Though fatality risk is low for the general population, those acquiring the disease whilst a patient carry a much higher chance of death. Increased awareness of the disease and how it can be acquired is essential – maybe we should be considering Legionnaires’ at the first sign of secondary or post-operative infection, rather than an after-thought?

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References

  • ABC.net (April 2017) ‘Melbourne Legionnaires’ outbreak that put five in hospital linked to CBD cooling towers’ retrieved from http://www.abc.net.au/news/2017-04-12/five-cases-of-legionnaires-disease-in-melbournes-cbd-investigate/8439660 last accessed 5 May 2017
  • Time, The Philadelphia Killer, (August 16, 1976) pages 64-65.
  • Health.vic (2015) ‘Legionellosis (Legionnaires’ Disease)’ retrieved from https://www2.health.vic.gov.au/public-health/infectious-diseases/disease-information-advice/legionellosis-legionnaires-disease last accessed 5 May 2017
  • Cdc.gov (May 2016) ‘Legionella (Legionnaires’ Disease and Pontiac Fever’ https://www.cdc.gov/legionella/about/diagnosis.html last accessed 4 May 2017
  • Stout JE, Yu VL. Hospital-acquired Legionnaires’ disease: new developments. Curr Opin Infect Dis. 2003 Aug;16(4):337-41.
  • Kool JL et al. (1998). More than 10 years of unrecognized nosocomial transmission of legionnaires’
    disease among transplant patients. Infection Control and Hospital Epidemiology, 19:898–904.
  • Strebel PM et al. (1988). Legionnaires’ disease in a Johannesburg teaching hospital. Investigation
    and control of an outbreak. South African Medical Journal, 73:329–333.

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