Low levels of the parasite Cryptosporidium were discovered in Druid Lake Reservoir, one of several open-air reservoirs that feed into the water supply for parts of Baltimore City and Baltimore County, as well as Howard County, the city Department of Public Works informed the public Thursday.

Cryptosporidium, or crypto for short, is known to cause gastrointestinal problems, especially among those with compromised immune systems, as well as the elderly and children, according to a release from the department.

Those with weakened immune systems and “other sensitive populations” are advised to drink bottled water, boil water for one minute before using, or filter tap water. People should discuss with their health care provider whether children and older adults should take these same precautions if they have concerns, said Dr. Tamara Green, chief medical officer for the Baltimore City Health Department.

According to Baltimore City’s advisory, people with compromised immune systems include those with HIV/AIDS, inherited diseases that affect the immune system, or cancer, and organ transplant patients who are taking certain immunosuppressive drugs.

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Green said the current low level of contamination in the water supply means the risk of developing symptoms of cryptosporidiosis — the disease caused by a crypto infection — is low for the general population with healthy immune systems. The most common symptom of cryptosporidiosis is watery diarrhea. Other symptoms include stomach cramps, dehydration, nausea, vomiting, fever or weight loss. People who are infected may not experience symptoms.

An interactive map shows impacted areas, which extend from the city through central and northern Baltimore County, including Towson, Parkville, Timonium and Cockeysville, where potable water is supplied by Baltimore City. Portions of southwestern Baltimore County and Elkridge in Howard County are also affected.

The city Department of Public Works said the detection of parasites is “not related, or in any way comparable, to previous water-related issues.” An E. coli outbreak in September 2022 prompted Baltimore City to institute a five-day boil-water advisory for about 1,500 homes and businesses, while tens of thousands of residents in West Baltimore and parts of Baltimore County were told to boil their tap water as a precaution.

“This is not E. coli,” said Faith Leach, the city’s chief administrative officer. “The concept of crypto in our water is new to us all,” she said, noting that there are no regulations for notification and testing post-contamination.

Cryptosporidium was found during a routine monthly test on Sept. 19, and due to the weeklong processing time of an outside lab, results were received by the city on September 26.

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Richard Luna, interim director for Baltimore City’s Department of Public Works, said DPW tested the water again yesterday, based on guidance from the Environmental Protection Agency, and stressed that the department will continue to coordinate closely with the federal agency to monitor and resolve the cryptosporidium contamination. Due to the lab’s processing time, however, results of the second sample will not be known for about another week.

DPW tests monthly for both cryptosporidium and giardia, another parasite that can cause intestinal illness, in the Druid Lake and Lake Ashburton reservoirs. According to the press release, DPW will test the water more frequently until the cryptosporidium contamination is resolved and is awaiting guidance from the Maryland Department of the Environment to determine how often to test.

The city began testing for both crypto and giardia after it was ordered to do so in May by the Environmental Protection Agency, when the agency imposed a consent decree. The EPA found the city had not been routinely testing the water supply, as required by the Safe Drinking Water Act.

The EPA had previously ordered Baltimore to install underground tanks at two of its open-air reservoirs — one of which is Druid Lake — by the end of 2018, and the agency found the city had failed to do so. Three other open-air drinking water sources managed by the city met federal standards years ago: The Towson reservoir in 2013, the Montebello reservoir in 2014 and the Guilford reservoir in 2019, according to the EPA order.

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Luna said DPW is on track to complete upgrades of the Ashburton reservoir by the end of November, and the Druid Hill reservoir by the end of the year.

Crypto is spread through the feces of an infected person or animal, and the parasite can be found in water, food, soil or on surfaces or unwashed hands, according to the Centers for Disease Control and Prevention. Symptoms of cryptosporidiosis typically appear between two and seven days post-infection, and usually last one to two weeks in people with healthy immune systems. Those infected with the parasite can continue to shed it and potentially infect others for weeks after symptoms stop.

Between 2001 and 2010, crypto was the leading cause of waterborne disease outbreaks linked to freshwater and coastal waterways used for public recreation. Cryptosporidiosis can be contracted by consuming contaminated water. The parasite’s high tolerance to chlorine enables it to survive for long periods of time in chlorinated drinking and swimming pool water, as well.

Speaking on WYPR’s Midday with Tom Hall, Baltimore County Executive Johnny Olszewski Jr. said the detection of a parasite in a facility that provides drinking water, which Baltimore City delivers to about 1.8 million homes and businesses, “reinforces why we need to have a governance structure that emphasizes” customers’ needs “are at the forefront.”

The task force, appointed jointly by the city and its suburban counterpart, was convened under state legislation in January requiring such a group study water and wastewater governance in the Baltimore region. They’re required to recommend how the system should be owned, run and managed, and deliver recommendations to city, county and Maryland leaders in January 2024.

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”Baltimore actually has some of the best drinking water in the nation — but we also know the infrastructure is aging,” Olszewski, a second-term Democrat, said. He recalled the E. coli outbreak last fall and the huge quantities of untreated sewage that were released into a Chesapeake Bay tributary by the city’s Back River Wastewater Treatment Plant before an explosion this spring, along with “years of neglect” at the Dundalk treatment plant, led to Maryland regulators to take control of the facility earlier this year.

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This story has been updated to correctly identify Lake Ashburton, and to note the number of open-air reservoirs managed by the city. It also has been updated to clarify the details of ongoing projects to install tanks for storing drinking water.

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