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It’s nearly certain the use of the Flint River as a municipal water source caused the outbreak of Legionnaires’ disease that killed 12 people and sickened 91 during the summers of 2014 and 2015, according to a team of scientists investigating the city’s water issues.

Conditions created by switching the city to the river water without adding proper corrosion controls in April 2014 created a perfect environment for the deadly Legionella bacteria to thrive, Virginia Tech Professor Marc Edwards told The News.

“We have very little doubt that the outbreak was caused by the switch to Flint River water,” Edwards said.

According to Edwards, the corrosive nature of the Flint River depleted bacteria-fighting chlorine residuals in the water. It also ate away at the pipes, filling the water with iron and rust, nutrients that Legionella feed on. At the same time, the temperature of water in the system increased slightly because the Flint River is warmer than the city’s previous source, Lake Huron, creating an incubator for pathogens.

“(Water) temperatures were also slightly elevated as well, as compared with historical levels, because of the Flint River source,” Edwards said. “It’s very, very likely that the removal of the disinfectant, higher iron and warmer temperatures caused the Legionella outbreak.”

Last week, Edwards’ team presented data showing Flint’s water system is recovering following a switch back to Detroit’s city water in October 2015. Pipes that were stripped of their protective coating by highly corrosive river water are healing, and lead and iron levels continue to drop. Much of the loose sediment that once turned the water brown has been flushed from the system.

The water is still not considered safe to drink without use of a filter.

Researchers tested water heaters in 30 homes in June for L. pneumophila serogroup 1, the deadly strain of bacteria that causes Legionnaires’ disease. They found culture-able levels in two out of the homes — what they described as a low number. They asked those homeowners to flush and scour their water heaters. They found no culture-able levels of the deadly pathogen when they returned to retest in November.

“We attribute (the absence of pathogens) to the fact that there were good chlorine residuals entering the homes at the time that we sampled,” said William Rhoads, a graduate student on Edwards’ team who researches Legionella in Flint.

Michigan officials didn’t agree with Edwards’ findings on Friday. State health officials have said they can’t link the outbreak with the water without an exact DNA match between Legionella found in a Legionnaires’ patient and bacteria found in the water.

The News reported in February the Michigan Department of Health and Human Services’ laboratory has eight clinical isolates, or cultures, of Legionella bacteria found in patients sickened during the outbreak, but they’ve never been compared to any other samples.

“Due to an inadequate number of clinical isolates, and the fact that environmental testing was not indicated by the epidemiology, MDHHS cannot conclude whether the outbreak is related solely to the events related to the water switch,” Eisner said in an email Friday. She added the isolates are still at the state laboratory.

“At the same time, the department recognizes how conditions for Legionella colonization in high-risk areas were optimized during the water switch. We continue to work with our partners to better understand the prevalence of Legionella bacteria within the Flint water system and to identify conditions that increase its growth.”

Eisner noted the state is challenging a protective order entered in Genesee County Circuit Court that limits the state health department’s ability to fully investigate Legionnaires’ cases in Genesee.

Dr. Janet Stout, a research associate professor with the University of Pittsburgh who has assisted with Legionnaires’ outbreaks in New York City and elsewhere, said the state should test its isolates against those collected from the environment, even if they only have eight.

“Based on the pattern of the cases of Legionnaires’ disease occurring right after the switch, and then disappearing after the change back to the Detroit water source, plus based on what I know about the microbiology of Legionnaires’ disease, I have said all along that they’re linked,” Stout said Friday. “There’s no question that they’re related.

Asked if the eight clinical isolates in the state’s possession are enough to determine a link to Flint’s water or another environmental source, Stout said: “That’s certainly enough.”

“I think when they say they’ll never know, it’s because at the time of the outbreak, despite the fact that some people like myself were saying, ‘test the water for Legionella,’ that was not done,” Stout said. “But I think they can still investigate that, and they should.”

The state health department has been under scrutiny for failing to notify the public about the outbreak until Jan. 13, when Gov. Rick Snyder held a press conference to announce it. The governor said he’d heard about the outbreak just two days before.

Several current and former state employees facing criminal charges for their alleged roles in the city’s water crisis will face preliminary examinations in 2017, nearly three years from when the city’s water problems began.

Genesee County Health Officer Mark Valacak thanked Edwards’ team for their investigation in Flint, but said he doesn’t think it should stop there.

“Edwards is definitely one of the experts in this area and has done a lot of research on this, and it is unfortunate, I think, that we couldn’t get the support from the state to do the testing when we had the concerns,” Valacak said Friday.

“I’d like to see the clinical isolates sent to the CDC for analysis.”

Also last week, researchers also presented results of a study that found Flint’s water was not the source of an outbreak of shigellosis that has sickened 180 people in Genesee and Saginaw Counties since March, causing no deaths. The number of cases peaked during the summer and has since declined.

The Shigella bacteria that causes severe diarrhea, abdominal pain and fever was not detected in any of 150 water samples drawn from 30 houses on the Flint water system.

Edwards said research has found residents’ fear of bathing over concerns about rashes and breathing difficulties is unfounded and may have contributed to the outbreak.

kbouffard@detroitnews.com

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