A microscopic parasite was detected in the Druid Lake Reservoir in Baltimore, and vulnerable residents are being told to take precautions when drinking water.

Traces of Cryptosporidium were found in the lake during a routine test by the Baltimore City Department of Public Works crew members.

Cryptosporidium is a microorganism which can cause gastrointestinal problems, including diarrhea, vomiting, fever, and stomach pain, according to a public works press release.

Children, the elderly, and those with an immunocompromising condition are more likely to experience these symptoms if exposed to the parasite.

"People with healthy immune systems typically are not impacted or quickly recover without medical treatment," the release noted.

This microorganism discovery only affects the water systems in Baltimore City and Baltimore and Howard counties in Maryland.

While Cryptosporidium poses potential health issues, the levels that were detected indicated "low risk for the general public" and do not pose an immediate health risk, according to DPW officials.

That means drinking water is still safe for most people in the city -- however, DPW advises vulnerable populations to drink bottled water, boil water for one minute before consuming or filter tap water.

DPW crews will continue to conduct testing until results show that Cryptosporidium is no longer detected.