Estimate of Burden and Direct Healthcare Cost of Infectious Waterborne Disease in the United States
We read with interest the article by Collier et al. (1), which includes an estimate of the economic burden of waterborne illness in the United States. While the study is noteworthy, comparisons of the burden estimates to a 2018 study of the economic burden of recreational waterborne illness (RWI) in the US by DeFlorio-Barker et al. (2) were lacking. The two studies report very different estimates of the number of cases of waterborne illness (Collier et al.: ~7.1 million total waterborne illnesses and DeFlorio-Barker et al.: ~90 million RWI). Collier et al. estimated total direct costs of all waterborne illness caused by 17 pathogens to be $3.3 billion, while DeFlorio-Barker estimated the costs of RWI alone to be $2.9 billion. Both the Collier and DeFlorio-Barker studies used similar methods to address underreporting and underdiagnosis of illness. Key differences between the two studies are: Collier et al. summarized health care costs associated with infections caused by 17 pathogens that might be waterborne, then relied heavily on expert judgment (3) to estimate the proportion of those illnesses attributable to water exposure. By contrast DeFlorio-Barker et al. used data from large cohort studies of water recreation to estimate the burden of RWI of mild and moderate severity, and outbreak data to estimate the burden of severe RWI. Collier et al. estimated the direct costs of illnesses while DeFlorio-Barker et al. estimated both direct and indirect costs (such as lost time from work). Because enteric pathogens responsible for gastrointestinal symptoms following water recreation are generally not identified on clinical testing (4), Collier et al.’s estimate of the economic burden of waterborne illness due to 17 pathogens substantially underestimates the overall number of cases and economic burden of waterborne illness.