This report describes CDC surveillance of waterborne disease outbreaks associated with drinking water during 2015–2020.

Cleaning and disinfection of frequently touched surfaces and frequent hand hygiene are recommended measures to prevent transmission of SARS-CoV-2, the virus that causes COVID-19. Since the onset of the COVID-19 pandemic, poison center calls regarding exposures to cleaners, disinfectants, and hand sanitizers have increased as compared with prior years, indicating a need to evaluate household safety precautions. An opt-in Internet panel survey of 502 U.S. adults was conducted in May 2020. Survey items evaluated knowledge regarding use and storage of cleaners, disinfectants, and hand sanitizers; attitudes about household cleaning and disinfection; and safety precautions practiced during the prior month. We assigned a knowledge score to each respondent to quantify knowledge of safety precautions and calculated median scores by demographic characteristics and attitudes. We identified gaps in knowledge regarding safe use and storage of cleaners, disinfectants, and hand sanitizers; the overall median knowledge score was 5.17 (95% CI: 4.85–5.50; maximum 9.00). Knowledge scores were lower among younger than older age-groups and among black non-Hispanic and Hispanic respondents compared with white non-Hispanic respondents. A greater proportion of respondents expressed knowledge of safety precautions than the proportion who engaged in these precautions. Tailored communication strategies should be used to reach populations with lower knowledge of cleaning and disinfection safety. In addition, as knowledge alone did not shape individual engagement in safety precautions, health promotion campaigns may specifically emphasize the health risks of unsafe use and storage of cleaners, disinfectants, and hand sanitizers to address risk perception.

Legionella, the bacterium that causes Legionnaires’ disease, can grow and spread in building water systems and devices. The COVID-19 pandemic impacted building water systems through reductions in water usage. Legionella growth risk factors can be mitigated through control measures, such as flushing, to address stagnation, as part of a water management program (WMP). A national lodging organization (NLO) provided WMP data, including Legionella environmental testing results for periods before and during the pandemic. The statistical analysis revealed an increased risk of water samples testing positive for Legionella during the pandemic, with the greatest increase in risk observed at the building’s cold-water entry test point. Sample positivity did not vary by season, highlighting the importance of year-round Legionella control activities. The NLO’s flushing requirements may have prevented an increased risk of Legionella growth during the pandemic. However, additional control measures may be needed for some facilities that experience Legionella detections. This analysis provides needed evidence for the use of flushing to mitigate the impacts of building water stagnation, as well as the value of routine Legionella testing for WMP validation. Furthermore, this report reinforces the idea that WMPs remain the optimal tool to reduce the risk of Legionella growth and spread in building water systems.

We piloted a methodology for collecting and interpreting root cause—or environmental deficiency (ED)—information from Legionnaires’ disease (LD) outbreak investigation reports. The methodology included a classification framework to assess common failures observed in the implementation of water management programs (WMPs). We reviewed reports from fourteen CDC-led investigations between 1 January 2015 and 21 June 2019 to identify EDs associated with outbreaks of LD. We developed an abstraction guide to standardize data collection from outbreak reports and define relevant parameters. We categorized each ED according to three criteria: ED type, WMP-deficiency type, and source of deficiency. We calculated the prevalence of EDs among facilities and explored differences between facilities with and without WMPs. A majority of EDs identified (81%) were classified as process failures. Facilities with WMPs (n = 8) had lower prevalence of EDs attributed to plumbed devices (9.1%) and infrastructure design (0%) than facilities without WMPs (n = 6; 33.3% and 24.2%, respectively). About three quarters (72%) of LD cases and 81% of the fatalities in our sample originated at facilities without a WMP. This report highlights the importance of WMPs in preventing and mitigating outbreaks of LD. Building water system process management is a primary obstacle toward limiting the root causes of LD outbreaks. Greater emphasis on the documentation, verification, validation, and continuous program review steps will be important in maximizing the effectiveness of WMPs.

Zoonotic transmission of Cryptosporidium parvum is often associated with ruminants. We report an investigation of cryptosporidiosis among persons who had contact with raccoons. In July 2024, 2 states identified 18 human cryptosporidiosis cases who volunteered at the same animal facility. One human specimen and 2 raccoon specimens tested positive for C. parvum. Molecular subtyping of the C. parvum (subtype IIaA15G2R1) suggested zoonotic transmission between raccoons, humans, or their shared environments. These findings can inform public health actions, developed in collaboration with specific populations (eg, wildlife rehabilitation facilities) and include interventions tailored to such settings to mitigate future outbreaks.

A better understanding of risk factors and the predictive capability of water management program (WMP) data in detecting Legionella are needed to inform the efforts aimed at reducing Legionella growth and preventing outbreaks of Legionnaires’ disease. Using WMPs and Legionella testing data from a national lodging organization in the United States, we aimed to (1) identify factors associated with Legionella detection and (2) assess the ability of WMP disinfectant and temperature metrics to predict Legionella detection. We conducted a logistic regression analysis to identify WMP metrics associated with Legionella serogroup 1 (SG1) detection. We also estimated the predictive values for each of the WMP metrics and SG1 detection. Of 5435 testing observations from 2018 to 2020, 411 (7.6%) had SG1 detection, and 1606 (29.5%) had either SG1 or non-SG1 detection. We found failures in commonly collected WMP metrics, particularly at the primary test point for total disinfectant levels in hot water, to be associated with SG1 detection. These findings highlight that establishing and regularly monitoring water quality parameters for WMPs may be important for preventing Legionella growth and subsequent disease. However, while unsuitable water quality parameter results are associated with Legionella detection, this study found that they had poor predictive value, due in part to the low prevalence of SG1 detection in this dataset. These findings suggest that Legionella testing provides critical information to validate if a WMP is working, which cannot be obtained through water quality parameter measurements alone.