While not the most common occupational disease, Legionnaires' disease has proven to be one of the more fatal ones - especially to more at-risk individuals. In fact, according to the Centers for Disease Control and Prevention (CDC), it's estimated that about one out of every 10 people who contract the illness will die from complications of it. This number increases to about 25 percent for elderly or immune-compromised individuals.

In this post, we'll cover everything you need to know about this disease - from legionnaires' disease prevention to legionnaires' disease in the workplace and everything in between.

What is Legionnaires' Disease?

Legionnaires' disease is a very severe type of pneumonia, or inflammation of the lung that's caused by an infection. The bacterium that causes the disease is legionella. In some cases, this legionella bacteria may lead to a less serious illness known as Pontiac Fever, which is similar to the flu. Pontiac Fever typically clears without any necessary medical intervention.

The same cannot be said of Legionnaires' disease. In fact, prompt medical treatment is the best path to a full recovery. Failure to seek immediate medical treatment could be fatal, especially if you meet certain risk factors (more on that below). As we said in the opening, about 10 percent of all people who contract the illness die due to complications from it.

Who is at risk of Legionnaires' disease? Some risk factors that can increase the chances of severe illness include:

  • Age (50 and up)
  • If you're a current or former smoker
  • If you have a chronic lung disease (i.e., emphysema, COPD, etc.)
  • If you have a weakened immune system or take medication that weakens your immune system


The symptoms of Legionnaires' disease are similar to other lung infections and include:

  • Cough
  • Shortness of breath
  • Muscle aches
  • Headache
  • High fever
  • Chest pain
  • Nausea

The mild version of Legionnaires' disease, Pontiac fever, doesn't tend to affect the lungs. Pontiac fever symptoms are like the flu and often include fever, chills, and muscle aches.

In dire cases, Legionnaires' disease can progress to cause respiratory failure, septic shock, or acute kidney failure - complications that can be life-threatening. Symptoms tend to develop anywhere from two to 10 days following exposure to the legionella bacteria.


Legionnaires' disease can be fatal if it's not treated in a prompt manner, so it's important to see your doctor or medical professional immediately after you begin experiencing symptoms or if you believe you're been exposed to the legionella bacteria.

Doctors take a chest x-ray and conduct a physical exam to diagnose pneumonia. They may also sample urine or phlegm to determine if the infection is the result of the legionella bacteria. Following diagnosis, Legionnaires' disease is best treated with antibiotics.

Legionnaires' Disease in the Workplace

Legionnaires' disease isn't the most common occupational disease. But it is a threat, and outbreaks are often linked to places that have large or complex water systems. The legionella bacteria easily spread through water and the disease is often contracted by inhaling small droplets of bacteria-containing water. Exposure is also linked to contaminated soil. Legionnaires' disease is not an illness that tends to be transmitted from person to person.

Common Sources of Outbreaks

  • Places that have potable water used for bathing
  • Cooling towers in air conditioning systems
  • Decorative fountains
  • Hot tubs, swimming pools, and whirlpools
  • Soil
  • Drinking water

Noting this, outbreaks are often linked to buildings or workplaces such as:

  • Hotels
  • Hospitals
  • Nursing homes
  • Molding manufacturers
  • Cruise ships
  • Vehicle manufacturers

Recommended PPE

All employers that have workers in at-risk environments should ensure their people are outfitted with the appropriate PPE in situations where an outbreak could be possible. Since Legionnaires' disease is often contracted by breathing in droplets of water that contain the legionella bacteria, a respirator is a key piece of safety equipment.

According to OSHA, workers should wear a NIOSH-approved respirator that features a minimum 95 percent efficiency in removing 0.3-micron particles. This is equivalent to an N95 respirator. Chemical protective clothing is also key to Legionnaires' disease prevention, especially for workers who are cleaning and disinfecting water systems. Chemical goggles, gloves and protective clothing should be worn accordingly in these situations.

OSHA Legionella Regulations and Safety Measures

Surprisingly, there is no OSHA standard that's specific for preventing Legionnaires' disease in the workplace. However, there are guidelines and other regulations that employers should follow to safeguard their workers.

  • Water sampling: The legionella bacteria thrive in certain water environments, which is why legionella CFU limits have been established. Aside from cooling towers, all water system types should have a measured concentration below 1 CFU/mL. Between 1 and 10 CFU/mL suggests that legionella growth is possible. Regular water sampling is key to keeping potable water at safe concentrations.
  • Routine maintenance and cleaning of water systems, especially in environments where people tend to be more at risk of developing severe disease (i.e., hospitals, nursing homes, etc.).
  • Routinely treating water systems with biocide to prevent or decrease the risk of legionella growth.
  • Water systems can also be treated in a non-chemical fashion, using ultraviolet light or ultrasonic waves - two practices that have demonstrated the ability to kill the legionella bacteria under the right conditions.

While Legionnaires' disease may not be the most common occupational health hazard, it certainly has the potential to lead to some significant health problems. And because transmission is preventable with the right mix of PPE and other preventative measures, now is the time to revisit your site-specific safety plan in at-risk environments.