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Clear water is not always a sign of clean water — or so suggest two new reports on water-associated disease outbreaks published Thursday by the US Centers for Disease Control and Prevention.

In 2013-14, a total of 42 drinking-water-associated outbreaks caused by infectious pathogens, chemicals or toxins were reported to the CDC from 19 states. The reports do not include lead contamination.

These outbreaks led to at least 1,006 cases of illness, 124 hospitalizations and 13 deaths across Alaska, Arizona, Florida, Idaho, Indiana, Kansas, Maryland, Michigan, Montana, New York, North Carolina, Ohio, Oregon, Pennsylvania, Rhode Island, Tennessee, Virginia, West Virginia and Wisconsin.

“The number of drinking water outbreaks has increased from 32 in 2011-2012,” said Kathy Benedict, lead author of the report and an epidemiologist in CDC’s Waterborne Disease Prevention Branch. “This may be due to a true increase in disease, better reporting or changes in capacity in states to do surveillance.”

Legionella caused more than half — 57% — of the outbreaks, 88% of the hospitalizations and all 13 deaths, according to the CDC. These bacteria causes legionellosis, a less severe version of the respiratory disease known as Legionnaire’s disease. Cough, shortness of breath, fever, and muscle and headaches are the symptoms.

Legionella bacteria are present in the environment and enter drinking water through various activities, including floods, explained Wilma Subra, president of the Subra Co., an environmental consulting firm. She was not involved in the CDC reports.

Though water systems frequently “chlorinate before they distribute,” Subra explained, in some cases, the level of chlorination “isn’t sufficient to make it all the way to the end of this distribution system.”

“So if these bacteria are in there and don’t get properly treated before they leave the plant … then the bacteria grows again and causes the people in the farthest regions of the distribution system to become contaminated and to become ill,” Subra said.

Cryptosporidium or Crypto, a parasite that causes a diarrheal illness, caused five outbreaks in the CDC report, and Giardia, another parasite leading to diarrheal illness, caused three outbreaks.

“Giardia is known to be active and alive in groundwater sources, particularly,” Subra said.

Five outbreaks were caused by chemicals or toxic algal blooms rather than bacteria or parasites.

The report said that 75% of the 1,006 cases of illness were linked to community water systems, which are government-regulated.

A related CDC report brought similar news.

Waterborne disease

During the same 2013-14 time frame, 15 outbreaks associated with an environmental exposure to water contaminated with harmful pathogens, chemicals or toxins were reported to the CDC by 10 states. A total of 226 cases of illness, 69 hospitalizations and nine deaths were recorded in Colorado, Illinois, Michigan, Minnesota, New Mexico, New York, Ohio, Pennsylvania, Utah and Virginia.

An additional 12 outbreaks caused by undetermined exposure to contaminated water were reported by eight states during the 2013-2014 period. Alabama, California, Kentucky, Montana, New York, Ohio, Pennsylvania and Texas together recorded 63 cases of illness, 39 hospitalizations and eight deaths.

Benedict said outbreaks associated with environmental exposure to water increased from eight outbreaks in 2011-2012, while no change occurred in undetermined exposure outbreaks.

Undetermined exposures could include cases in which, for example, an unreported spill of chemicals or waste products into the Mississippi River causes illness downriver.

“By the time everyone was really ill, that slug of water had gone through the system, and so it was indeterminate what that contaminant was,” Subra said.

For the combined environmental and undetermined disease outbreaks, Legionella was responsible for 63% of the illnesses, 94% of hospitalizations and all deaths.

Among the environmental exposure outbreaks, eight involved human-made systems, such as cooling towers and decorative fountains, while seven involved natural water bodies, such as rivers and streams, according to the CDC. Giardia caused most of the natural water illnesses.

“In general, there are fewer waterborne disease outbreaks reported today in comparison to the late ’70s or early ’80s,” said Benedict. Yet she also noted that the “data likely do not capture all of the outbreaks or cases that occurred” during the 2013-14 time period due to variations in surveillance and reporting among the states.

Combined, the two reports suggest action is needed.

Aging infrastructure, no funds

“I see aging infrastructure is one of the major, major, major sources of the problem,” Subra said. “And it’s because a lot of these smaller, poorer communities just don’t have the resources to put into infrastructure repair, and they also can’t afford to get a loan, because they can’t afford to repay it.”

A second major problem is the source: where the raw water comes from.

“Whether it be surface water or groundwater, it has a lot of contaminants that historically have not been monitored for,” Subra said. In recent years, we have become more knowledgeable about new chemical contaminants. “Those materials were missed, and it was degrading our water quality and not being accounted for. And then of course you have the potential for all the bacterial contamination.”

Historically, water systems would test for bacteria from leaks at sewage plants and septic tanks, but they weren’t looking “for all the other things,” she said. “So you have chemical contamination and bacterial contamination that you weren’t looking out for historically that are also now contaminating the water and causing severe health impacts to the community.”

Though environmental scientists figured these issues were happening, there was no testing to verify them and no requirements at the federal or state level that tests be done by water systems.

What’s a water-drinking human to do?

“Citizens can become educated and empowered in order to bring these issues to the forefront — to their elected official, to the regulatory agencies,” Subra said. “It’s really up to the citizens to be able to identify what’s going on with their drinking water source.”

If people think their water may be contaminated, they should “absolutely” test their own water, she added. “However, there are so many of those people who have individual wells who don’t have the resources to pay for testing.”

Benedict said, “Providing safe drinking water was one of the most important public health achievements of the 20th century.” She added that “investments in upgrading and maintaining drinking water treatment and distribution systems are important to continue providing safe water to communities in the US.”

On the household level, though, it may not always be clear when water is polluted.

“If you have iron in your water, you get this orangey-red-brown slimy sediment in your water, and you know something’s wrong,” Subra said. “A lot of these bacteria and chemicals are colorless, odorless, and you aren’t aware the quality of your water is bad until you consume it and become ill.”