RPLP1 and legionellosis: A confirmed case of legionellosis requires clinically compatible symptoms and at least one confirmatory laboratory test, including isolation of Legionella from respiratory secretions (or other normally sterile sites), detection of Legionella pneumophila serogroup 1 (Lp1) using the urinary antigen test (UAT), and/or a 4-fold or greater rise in antibody titer to Lp1 antigen between acute and convalescent-phase serum (https://www.cdc.gov/legionella/health-depts/surv-reporting/case-definitions.html).