Risk Communication and Infodemic Misframing in Legionella spp. Environmental Surveillance: An Infodemiology Case Study

Travel-associated Legionnaires' disease (TALD) events can generate public concern when environmental surveillance findings are communicated without an adequate explanation of the results. This study examined how surveillance data on <i>Legionella</i> spp. were framed and amplified during a TALD-related investigation in Crete, Greece, from June to July 2025. A mixed infodemiology and environmental surveillance approach was applied, including the analysis of 95 online media items across nine languages, Google Trends search-interest data, and hotel water-system surveillance data from epidemiologically linked facilities. Sampling conducted in a limited number of hotels associated with TALD cases indicated that approximately 50% of the water samples exceeded the laboratory reporting limit of ≥50 CFU/L for <i>Legionella</i> spp., a numerically correct but context-specific finding. Numerical misframing occurred in 83.7%, 41.7%, and 18.2% of Greek, German, and English language items, respectively, with significant differences across language markets (χ² (8) = 43.75, <i>p</i> < 0.0001; Cramér's V = 0.679). Public search-interest signals were transient and geographically limited. Environmental surveillance showed no increase in <i>Legionella pneumophila</i> risk, with similar proportions of samples ≥50 CFU/L in the pre-/peri-infodemic (January-July 2025) and post-infodemic (August-November 2025) periods (23.11% [95% CI: 18.21-28.87] vs. 24.45% [19.34-30.41]) and similar exceedance of ≥1000 CFU/L (13.45% [9.69-18.36] vs. 14.41% [10.45-19.55]). Overall, the loss of contextual interpretation of surveillance results and conflation of laboratory reporting limits with regulatory thresholds were associated with inconsistent public risk perception, without evidence of increased environmental hazard.