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.
"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.
Legionella caused more than half — 57% — of the outbreaks, 88% of the hospitalizations and all 13 deaths, according to the CDC.
"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.
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.
An additional 12 outbreaks caused by undetermined exposure to contaminated water were reported by eight states during the 2013-2014 period.
"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."
"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.