Epidemiologic Aspects of Waterborne Infectious Disease

Public health surveillance and epidemiologic research can inform environmental microbiology research and practice. Likewise, advances in environmental microbiology improve our understanding of waterborne disease transmission and support targeted public health actions. Waterborne disease outbreak investigations provide useful information about clusters of uncommon but clinically significant infections caused by recognized pathogens. Furthermore, factors that resulted in outbreaks are often characterized and prevention strategies can be developed. Cohort studies of acute waterborne illness provide information about common but mild sporadic cases of illness. In some settings (but not others) such studies have identified microbial measures of water quality that predict illness occurrence. However, pathogens and environmental factors that caused sporadic cases are generally not identified. The majority of recognized waterborne disease outbreaks in the United States occur in the context of recreation in swimming pools, water parks, and other treated waters, with Cryptosporidium spp. the agent responsible for the vast majority of cases. Recognized outbreaks at lakes and rivers are caused by a wider array of infectious agents. Outbreaks linked to drinking water tend to be caused by deficiencies in water treatment and distribution, with bacteria as the causative agents of most outbreaks. Emerging concerns that have been the focus of recent research include respiratory disease attributable to biofilm-associated microbes in drinking water systems, illness caused by toxins elaborated by algal blooms, and associations between precipitation and waterborne disease.