It’s quite common to find Legionella species other than Legionella pneumophila in cooling towers and water distribution systems. To date, more than 58 Legionella species have been described in published articles. Of these approximately 25 are linked to disease, namely Legionella pneumophila species serogroup 1, 3, 4, and 6.
Legionella pneumophila serogroup 1 is the most virulent strain causing the majority of infections. The remaining non-pneumophila species (found in water and soil) are considered nonpathogenic until shown to cause disease. Of the CDC reported cases less than 5% is attributed to non-pathognenic species. Since risk for infection is rare, adjusting your response to an adequate threat level is appropriate.
To learn more, click the table rows below for each Legionella species.