Legionellae are common contaminates of artificial water systems, including air-conditioning systems, cooling towers, and jacuzzis where conditions may be optimal for growth and proliferation. Once aerosolized, the bacteria can enter the human respiratory tract and cause disease manifesting as Legionnaires’ disease, a severe form of pneumonia, or Pontiac fever, a self-limiting flu-like illness. Symptoms include fever, chills, muscle aches, headaches, cough, nausea and diarrhea. Onset occurs between 2 and 10 days after exposure.
Health Departments reported nearly 10,000 cases of Legionnaires’ disease in the US in 2018. However, because Legionnaires’ disease is likely underdiagnosed, this number may underestimate the true incidence. About one in 10 people who gets sick from Legionnaires’ disease will die.
Many labs use rapid urine antigen tests for L. pneumophila. However, this test is intended for the detection of serogroup 1(sg1) and may miss a diagnosis of Legionnaires’ disease caused by other serogroups or other Legionella spp. The new WSLH assay allows simultaneous detection and differentiation of Legionella spp., Legionella pneumophila, and Legionella pneumophila sg1 from clinical specimens. The assay targets the ssrA (Legionella species) gene, the mip (L. pneumophila) gene, and the recently identified wzm gene, specific for L. pneumophila sg1. This protocol was adapted from a CDC protocol. It has been validated for use at the WSLH. It has not been cleared by the U.S. Food and Drug Administration.