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 adequate ex-planation of the results. This study examined how surveillance data on Legionella spp. were framed and amplified during a TALD-related investigation in Crete, Greece, between June and July 2025. A mixed infodemiology and environmental surveillance approach was applied, including analysis of 95 online media items across nine lan-guages, 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 water samples exceeded the laboratory reporting limit of ≥50 CFU/L, a numerically correct but con-text-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, p < 0.0001; Cramér’s V = 0.679). Public search-interest signals were transient and geographically limited. Environmental sur-veillance showed no increase in Legionella pneumophila risk, with similar proportions of samples ≥50 CFU/L in the pre-/peri-infodemic (Jan–Jul 2025) and post-infodemic (Aug–Nov 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, loss of contextual interpretation of surveillance results and conflation of laboratory re-porting limits with regulatory thresholds were associated with inconsistent public risk perception, without evidence of increased environmental hazard.