Infectious Disease
An increase in legionellosis cases in the US: An Epidemiological trend assessment before, during, and after the COVID-19 pandemic Katrina Stadler* Katrina Stadler Stadler Stadler Stadler Stadler Insight Exposure & Risk Sciences Group, Boulder, CO
We conducted a preliminary epidemiological assessment of legionellosis cases reported in the United States (US) by evaluating trends before, during, and after the World Health Organization’s (WHO) announcement of the end of the COVID-19 pandemic on May 5, 2023. Publicly available data from the Center for Disease Control and Prevention’s National Notifiable Diseases Surveillance System (NNDSS) for the years 2016 to 2023 were used in our analyses. T-tests were used to assess differences in the annual number of legionellosis cases before and during the COVID-19 pandemic (2016-2019 and 2020-2022 respectively), as well as for the differences in the monthly number of legionellosis cases before and after the pandemic was declared over (January-April 2023 and May-December 2023 respectively). Overall, the preliminary data show that there was an 8.44% decrease in the average number of legionellosis cases reported during the pandemic (2020 to 2022) compared to prior to the pandemic (2016-2019), however the decrease in the average number of cases was not statistically significant (p>0.1). Notably, there was a statistically significant increase (8.63%) in the average number of cases reported per month in 2023 after the WHO declared the end of the pandemic in May 2023 compared to the four months prior (p<0.001). This analysis suggests the possible influence of post pandemic conditions or activities (e.g., return to work and/or habitation of previously closed buildings, increased recreational activities, and travel) on the growing trend of legionellosis cases in the US.