Winter 2017

Pathogens in Your Plumbing

Unregulated older parts of our water distribution systems threaten to spread illness at ever-higher costs.

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An image of Legionella pneumophila bacteria. Photo: Science Source

An analysis of some 100 million Medicare records for U.S. adults ages 65 and older revealed the enormous scale and cost of infections linked to opportunistic “plumbing pathogens” that live inside drinking water distribution systems, including household and hospital water pipes.

The team, led by researchers from the Friedman School of Nutrition Science and Policy and Tufts School of Medicine, found that between 1991 and 2006, more than 617,000 hospitalizations related to three common plumbing pathogens—Legionella pneumophila, Mycobacterium avium and Pseudomonas aeruginosa—resulted in around $9 billion worth of Medicare payments, for an average of $600 million a year. The costs may now exceed $2 billion for 80,000 cases per year, according to the study authors.

“Premise plumbing pathogens can be found in drinking water, showers, hot tubs, medical instruments, kitchens, swimming pools—almost any premise where people use public water,” said lead study author Elena Naumova, a professor at the Friedman School, director of the Tufts Initiative for Forecasting and Modeling of Infectious Disease and an adjunct professor of public health and community medicine.

“The observed upward trend in associated infections is likely to continue, and aging water distribution systems might soon be an additional reservoir of costly multidrug resistance,” Naumova added. The study was published online in the Journal of Public Health Policy.

State and federal oversight generally has ensured the safety and quality of public drinking water in the U.S. However, the so-called premise plumbing systems—the pipes and fixtures in homes and buildings that transport water after delivery by public water utilities—are largely unregulated. This gap can lead to inconsistent monitoring and reporting of potentially harmful flaws, as was shown in the recent case of Flint, Michigan, where thousands of children were exposed to elevated levels of lead in the drinking water.

Opportunistic premise plumbing pathogens, such as the bacteria that cause Legionnaire’s disease, can thrive in low-nutrient conditions and grow as biofilms on the inner surfaces of pipes. Biofilms allow these pathogens to resist disinfectants and environmental stressors and aid in the spread of antibiotic resistance and virulent genes. As water distribution systems age, their susceptibility to contamination increases.

“The risk of becoming ill from drinking water is much less than the risk of becoming ill from food, but it is not zero,” noted Jeffrey Griffiths, a professor of public health and community medicine and an author of the study.

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