Deciding Whom to Test in Healthcare Settings

The problem

CDC receives reports of cases of healthcare-associated Legionnaires' disease from across the country. According to an analysis published in 2017, 76% of the jurisdictions analyzed reported a definite case of healthcare-associated Legionnaires' disease1.

When it occurs, healthcare-associated Legionnaires' disease is often severe. Data show the case fatality rate is 25% for definite healthcare-associated cases compared with 10% for cases that aren't healthcare-associated1.

Definite healthcare-associated was a classification used prior to 2020 to indicate patients that were hospitalized for the 10 days prior to illness onset. The current case definition has categories for healthcare association: possible and presumptive.

Deciding whom to test

See general indications for Legionnaires' disease testing.

Guidance for public health officials and healthcare providers

In healthcare settings, consider Legionnaires' disease testing for hospitalized patients with risk factors and pneumonia2. Patients with healthcare exposure in the 14 days prior to onset of pneumonia symptoms should be evaluated for Legionnaires’ disease. This is true even if they don’t meet the traditional definition for healthcare-associated pneumonia (with onset ≥48 hours after admission).

This is especially important among patients with severe pneumonia, in particular those requiring intensive care.

It's also important if the healthcare facility has had any of the following:

• Healthcare-associated Legionnaires' disease diagnosed in the past 12 months
• Positive environmental tests for Legionella
• Current changes in water quality that may lead to Legionella growth

Examples of water quality changes include

• Areas of stagnation
• Low residual disinfectant levels
• Nearby construction or a water main break
• Temperatures permissive to Legionella growth