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Legionella and Dormant Water Systems: A COVID-19 Shutdown Health Risk


NOTE:  The following information was published May 28, 2020. For current COVID-19 information, visit

As more and more counties move to the yellow phase of reopening during the COVID-19 pandemic, organizations are finding ways to operate safely. Companies are creating policies to offer guidance on wearing masks, cleaning and social distancing, but there is another important health risk that shouldn’t be overlooked – Legionnaires’ disease. Organizations that closed during the pandemic kept people out of their buildings, but Legionella bacteria may have been growing behind the closed doors.

We talked with (now retired) Carmine Pellosie, DO, Executive Director of HealthWorks and an Occupational and Environmental Medicine specialist, to gain insight into this bacteria, from how to prevent it to the illness it causes.

What buildings are susceptible to Legionella bacteria?

Buildings where water systems have been sitting or stagnant or buildings with cooling towers are especially at risk for developing excessive growth of Legionella in their system. This includes any premise’s pipes and water-heating equipment. Decorative water fountains, water features and hot tubs are also known risks.

How is Legionella spread?

This bacteria is spread through water droplets containing the bacteria, which can be inhaled in showers, central air conditioning systems, or if water containing the bacteria is accidentally aspirated into the lungs while swallowing. It does not spread from person to person.

What are the symptoms of Legionnaires’ disease?

Legionnaires’ disease causes the same symptoms as pneumonia (lung infection), which include cough, shortness of breath and fever. Other symptoms include muscle aches, headaches, diarrhea, nausea and confusion. These symptoms usually begin two to 10 days after exposure to the Legionella bacteria, but some people may take up to two weeks to develop symptoms.

Many of those who become ill with Legionnaires’ disease need to be hospitalized but are able to make a full recovery. However, about 1 out of 10 people who get Legionnaires’ disease will die from the infection. Risk factors for complications include:

  • 50 years or older

  • Smoking regularly or having smoked regularly in the past

  • Chronic lung disease (like chronic obstructive pulmonary disease or emphysema)

  • A weak immune system, including a weakened immune system as a result of taking certain medications

  • Cancer

  • Underlying illnesses such as diabetes, kidney failure or liver failure

What are steps businesses can take to prevent accidental exposure to Legionella?

First, awareness is key. Before reopening buildings, especially if water systems have been sitting, planning should occur. Building owners should check the water systems and develop a water management plan. An essential starting point is the Legionnaires’ disease information on the OSHA website as well as the CDC toolkit for developing a water management program to reduce Legionella growth and spread in buildings. There are many considerations for implementation of a water management plan as described in the OSHA and CDC information. This includes water quality testing, testing for bacteria and disinfectant level testing.

What are signs that Legionella is present?

A slimy growth (biofilm), scaling or sediment may be noted in some water systems. That being said, the bacteria can be totally invisible to the human eye and odorless.

Any water system that has been sitting or stagnant, heats water or is associated with a cooling tower or water feature should be suspect and requires further inspection and attention. In addition, construction in or around the building or disruptions in water systems can increase Legionella risk.

If anyone is associated with the building has a known diagnosis of Legionnaires’ disease, the local health department should be contacted to assist.

What is the treatment for Legionnaires’ disease?

A health care professional will investigate for the cause of any illness with similar symptoms to Legionnaires’ diseases with certain tests. When the cause of the illness is identified as Legionnaires’ disease, antibiotics are prescribed for treatment. Other supportive care may be needed, especially in the hospitalized ill patient.

If you think you have symptoms of Legionnaires’ disease, visit your primary care provider. To find a primary care provider near you, go to


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