The immunocompromised, kids and seniors advised to avoid drinking water in parts of Baltimore area after parasite detected

Baltimore City officials are advising immunocompromised individuals, children and senior citizens to avoid drinking tap water across a large swath of its service area in the city, Baltimore County and a small part of Howard County due to parasitic contamination.

Testing has detected low levels of a microscopic parasite called cryptosporidium in Baltimore’s drinking water reservoir at Druid Lake, officials announced Thursday.

Vulnerable people in the affected area are advised to boil their drinking water for one minute, to drink bottled water or to drink water filtered through filters equipped to remove objects 1 micron or larger.

The affected area stretches across city from southwest to northeast Baltimore, including much of West and North Baltimore, and north and east into Baltimore County, from Towson up through Hunt Valley to Cockeysville and Sparks and including Parkville, Perry Hall and Overlea, according to a map shared by Baltimore City’s Department of Public Works. It also reaches in southwest into Baltimore County to include Arbutus and into Howard County’s Elkridge along Route 1.

Officials said the low concentration of the parasite presents a low risk to the general public, but cryptosporidium can cause gastrointestinal problems, including diarrhea, stomach cramps and nausea.

Therefore, immunocompromised people, including those with HIV/AIDS and cancer, transplant patients taking immunosuppressive drugs and those with other conditions of the immune system, are urged to take precautions.

So far, no cases of cryptosporidiosis, the illness caused by the bacteria, have been reported in the city within the last two months, said Tamara Green, chief medical officer at the Baltimore City Department of Health.

“For most people, if they have a healthy immune system, they will not have any symptoms,” Green said. “But we want people to be vigilant and monitor their symptoms.”

On Tuesday, the city received the results from a laboratory indicating that samples collected Sept. 19 contained a 0.09% concentration of the parasite, said Richard Luna, the interim director of the city’s Department of Public Works. The city announced the contamination Thursday morning.

During a news conference Thursday, Luna said that the city notified the Maryland Department of the Environment and the federal Environmental Protection Agency on Tuesday, and the agencies have been collaborating on the public communication strategy.

“For us, it’s really important to give you the right information as quickly as possible, but to really look at those communications prior to, so that they’re clear and understandable for the public,” Luna said.

The city was heavily criticized last year for what some called a slow response to and announcement about the discovery of E. coli bacteria in tap water in West Baltimore during routine testing. In that instance, the city also took about two days to notify the public.

During Thursday’s news conference, City Administrator Faith Leach drew a distinction between the E. coli contamination and the cryptosporidium contamination. The E. coli contamination resulted in a weeklong “boil water advisory” for all residents in the affected area — not just vulnerable residents — because it was considered more dangerous.

“I don’t want to conflate E. coli with cryptosporidium. These two are completely different things,” Leach said. “The big takeaway ... is that we believe that our drinking water remains safe for the general population.”

The Druid Lake Reservoir holds water that already has been treated by the city’s facilities, and is later sent to homes and businesses in the city and surrounding counties. Construction crews are working to replace the open-air reservoir with underground storage tanks in an effort to protect the water from contaminants. It’s a project that has been marred by years of delays, and earlier this year, the federal Environmental Protection Agency served the city an order to cover the reservoir, and a second open-air reservoir at Lake Ashburton, by the end of the year.

The order also included a mandate that the city initiate monthly testing for giardia and cryptosporidium while the reservoirs remained uncovered. That testing began in late July and early August, Luna said. Those initial samples indicated no evidence of contamination.

The raw water from the city’s reservoirs at Loch Raven, Prettyboy and Liberty, which is later treated for contaminants like cryptosporidium, also does not show evidence of contamination, according to a news release from the city.

Luna said the efforts to get the covered water sources online are proceeding according to the EPA-mandated schedule, with the Ashburton project expected to finish by Nov. 30, and the Druid project by Dec. 30.

The levels of cryptosporidium in the water at Druid Lake were “so low that it was even hard for the laboratory analyst to detect” the parasite, Luna said.

“They stated to us that it would be too difficult to pinpoint the exact source of that bacteria,” Luna said.

City officials studied the water system in order to determine all of the possible areas in the city and surrounding counties that could have received the contaminated water, which already would have been distributed by the time the city received the positive result, Luna said.

“Our analyzers looked at all of the modeling data to see: Water that was released through Druid Lake: Where did that end up in our system?” Luna said. “And so overall, that map that you see is probably the largest capture of where that water could have gone.”

The city has yet to announce whether there are plans to distribute bottled water in impacted areas, but that is being “coordinated internally,” Luna said.

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