THIRTY-THREE years ago, United States newscast carried information about the outbreak in Pennsylvania of a mysterious disease called Legionnaires’ disease. It brought to mind ancient Rome, as the term legionnaire refers to a member of a legion or battalion of soldiers of that era.

I had also heard of the French Foreign Legion, a military service branch of the French Army established in 1831, which was primarily used to protect and expand the French colonial empire during the 19th century. Back then I associated Legionnaires’ disease with soldiers and, by extension, battle action.

The news informed the public about an outbreak of severe pneumonia (lung infection) among the participants of an American Legion Convention in Philadelphia, Pennsylvania. The American Legion is a wartime veterans service organisation.

Following the outbreak, America’s Centers for Disease Control (CDC), in cooperation with other federal, state, and local authorities, launched one of the largest disease investigations in US history.

CDC identified a new bacterium (Legionella pneumophila) that, it discovered, was spread through the hotel’s air conditioning system. Three days after the convention ended, the first victim died.

Within a week, more than 200 people, mostly men, had been hospitalised, and 34 had died. All had attended the convention and stayed at the same hotel. The Legionella bacterium got its name from this disease outbreak.

Legionnaires’ disease is a severe form of pneumonia — lung inflammation usually caused by infection. The Legionella bacterium also causes Pontiac fever, a milder illness that resembles acute influenza and which often goes undiagnosed. It may produce signs and symptoms including fever, chills, headache and muscle ache. Pontiac fever doesn’t infect your lungs, and symptoms usually clear up within two to five days.

Separately or together, the two illnesses are sometimes called Legionellosis. Legionellosis is a collection of infections that emerged in the second half of the 20th century. Pontiac fever usually clears on its own, but untreated Legionnaires’ disease can be fatal.

Legionnaires’ disease typically manifests itself two to 10 days after exposure to legionella bacteria. It frequently begins with the following signs and symptoms: Headache; muscle pain; chills; and fever that may be 104 F (40 C) or higher.

By the second or third day, patients will develop other signs and symptoms that may include: Coughing, which may bring up mucus and sometimes blood; shortness of breath; chest pain; gastrointestinal symptoms, such as nausea, vomiting and diarrhoea; confusion or other mental changes.

Although Legionnaires’ disease primarily affects the lungs, it can also cause infections in other parts of the body, including the heart.

If you have symptoms

See your doctor if you think you’ve been exposed to legionella bacteria. Diagnosing and treating Legionnaires’ disease as soon as possible can shorten the recovery period and prevent the occurrence of serious complications.

For people at high risk, prompt treatment is critical. Although prompt treatment with antibiotics usually cures Legionnaires’ disease, some people continue to experience problems after treatment.

How the infection spreads

Water is the major natural reservoir for legionella bacteria. Outdoors, the bacteria survive and rarely cause infections. Indoors, though, legionella bacteria can multiply in all kinds of water environment, such as:

• Water systems in hotels, hospitals and nursing homes;

• Hot tubs and whirlpools on cruise ships;

• Cooling towers in air conditioning systems;

• Irrigation systems;

• Decorative fountains;

• Swimming pools;

• Physical therapy equipment.

Legionella typically lives in nature at low concentrations, in groundwater, lakes, and streams. After entering man-made equipment, however, given the right environmental conditions, it may reproduce.

Most people who become infected have inhaled microscopic water droplets containing legionella bacteria. This might be the spray from a shower, faucet or whirlpool, or water dispersed through the ventilation system in a large building.

Although legionella bacteria are primarily spread through airborne water droplets, the infection can be transmitted in other ways, including: Aspiration, that is when liquids accidentally enter your lungs, usually because you cough or choke while drinking. If you aspirate water containing legionella bacteria, you may develop Legionnaires’ disease.

Risk factors

Exposure to legionella bacteria does not mean that you will automatically become sick. Some people are more at risk than others.

Smokers, for example, are in the high-risk group, as smoking damages the lungs, creating conditions for all types of lung infections.

At-risk individuals also include individuals who have a chronic lung disease such as emphysema or other serious conditions such as diabetes, kidney disease or cancer.

People who have a weakened immune system as a result of HIV/AIDS or certain medications, especially corticosteroids and drugs taken to prevent organ rejection after a transplant, are also among those at risk, as are individuals who are above 50 years of age. Legionnaires’ disease may also present itself in hospitals and nursing homes, where germs may spread easily and people are vulnerable to infection.

Complications

Legionnaires’ disease can lead to a number of life-threatening complications, including: Respiratory failure, when the lungs can no longer provide the body with enough oxygen or can’t remove enough carbon dioxide from the blood; septic shock, when a severe, sudden drop in blood pressure reduces blood flow to vital organs, especially to the kidneys and brain; acute kidney failure, when the kidneys cannot filter waste material from the blood resulting in the accumulation of dangerous levels of fluid and waste.

When not treated effectively and promptly, Legionnaires’ disease may be fatal. The good news is that outbreaks are preventable, but prevention requires meticulous cleaning and disinfection of water systems, pools and spas.

Local firm Technological Solutions Limited (TSL) routinely carries out inspection and preventive strategies to control Legionnaires’ disease among a number of establishments, primarily in the hospitality sector, including hotels and restaurants. Water testing for this organism is particularly useful for the tourism industry.

George Blake, TSL’s audit and technical services support manager who leads these audits, notes that he looks for the points at which control measures will be most effective.

“Control of legionella growth can occur through chemical or thermal methods,” he advises. “With thermal methods, we look to temperature control — which means keeping all cold water below 25 °C (78 °F) and all hot water above 51 °C (124 °F). This may require retrofitting existing complex distribution systems in large facilities.

“Moist heat sterilisation (superheating to 140 °F (60 °C) and flushing) is a non-chemical treatment that, typically, must be repeated every three to five weeks. Chlorine is a very effective chemical treatment. High levels of chlorine kill both the legionella bacteria and the host organisms.

“Annual hyperchlorination can be an effective part of a comprehensive legionella preventive action plan,” Blake added.

Approved Codes of Practice recommend that the risk assessment for legionella should be reviewed at least every two years or wherever there is reason to suspect that the preventive system is no longer valid, such as where water systems have been amended or modified.

Assessment should also be carried out if the use of the water system has changed, or if there is reason to suspect that legionella control measures are no longer working.

Dr Wendy-Gaye Thomas is group technical manager, Technological Solutions Limited, a Jamaican food technology company. Email her at: wendy.thomas@tsltech.com.