CDC study reveals increase of biofilm in US water systems

Due to the country’s aging infrastructure, the CDC expects a further increase to the transmission of diseases through biofilms and water systems.


The Centers for Disease Control and Prevention (CDC) recently released a new analysis of infectious waterborne diseases in the United States revealing that although large outbreaks associated with public drinking water systems have sharply declined, waterborne illnesses caused roughly 6,630 deaths and $3.3 billion in healthcare costs during a single year.

According to the study, the “transmission of disease via drinking water systems still occurs, often attributable to aging infrastructure, operational challenges, and the private or unregulated water systems (e.g., private wells) that serve an estimated 43 million persons. At the same time, the complexity and scope of water use has increased; drinking, sanitation, hygiene, cooling, and heating needs are supported by 6 million miles of plumbing inside US buildings (i.e., premise plumbing). Premise plumbing water quality can be compromised by long water residency times, reduced disinfectant levels, and inadequate hot water temperatures, creating environments where pathogens (e.g., nontuberculous mycobacteria [NTM], Pseudomonas, and Legionella) can amplify in biofilms. People can be exposed to these pathogens through contact, ingestion, or inhalation of aerosols (e.g., from shower heads, building cooling towers, or decorative fountains).”

Biofilm, a glue-like mixture of bacteria, fungi, amoebas, and other microorganisms, occur in water lines when taps are not turned on for extended periods of time, allowing stagnant water to accumulate. The report identified 17 different diseases, resulting in over 7 million waterborne illnesses each year, over 600,000 annual visits to emergency rooms, 118,000 hospitalizations, and 6,630 deaths in 2014.

“If you’ve ever felt that slimy film on your teeth when you haven’t brushed in a while, that’s a biofilm,” lead author Sarah Collier, an analytic epidemiologist at the CDC, told CNN. “Biofilms tend to form anywhere there’s microbes and water.”

Swimming pools, waterparks, water playgrounds, hot tubs, and other venues that rely largely on chlorination as the major barrier against disease transmission have been unable to prevent outbreaks of cryptosporidium, which is extremely chlorine resistant and has a low infectious dose.

Otitis externa, commonly known as swimmer’s ear, was identified in 4.7 million cases, accounting for 65% of annual waterborne illnesses and 20% of hospitalizations. Norovirus infections, known as the winter vomiting bug, were the second most commonly recorded waterborne transmissions, with 1.3 million cases, followed by the diarrheal disease giardiasis.

Most hospitalizations and deaths were caused by biofilm-associated pathogens (nontuberculous mycobacteria, Pseudomonas, Legionella), costing $2.39 billion annually in the U.S. Approximately 7.15 million waterborne illnesses occur annually, incurring $3.33 billion in direct U.S. healthcare costs.

Due to the country’s aging infrastructure, the CDC expects a further increase to the transmission of diseases through biofilms and water systems. The agency recommends running the water in your faucets for a couple minutes if you have not used them in a while, regularly flushing your water heater, and emptying your humidifiers to prevent an increase in stagnant water and biofilms.


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