Kingston, Ontario, is grappling with a stomach illness outbreak that has now affected 114 people, according to local health officials. Southeast Public Health is leading the investigation into the cluster of cryptosporidiosis cases, which began in early May 2026 and was officially identified on June 4, 2026.
Dr. Ethan Toumishey, deputy medical officer of health at Southeast Public Health, says the number of cases is highly unusual for the region. “The common experience of cryptosporidiosis in Ontario is sporadic cases that people might be exposed to in more limited numbers,” he explained. “So this is definitely a very significant signal that we’re seeing.”
Cryptosporidiosis is caused by a microscopic parasite called Cryptosporidium. It spreads when people swallow contaminated food or water, or through contact with infected feces from animals or people. Symptoms include watery diarrhea, nausea, vomiting, stomach pain, fever, and fatigue. They can start two to ten days after exposure and typically last one to two weeks. Some people may feel better for a few days and then get sick again before recovering fully.
Health officials have tested water samples from multiple locations across Kingston, including the water treatment plant run by Utilities Kingston. All samples came back negative for the parasite. The source of the outbreak is still under investigation. While the parasite can be spread through contaminated food, the health unit has said its investigation has not yet led to testing any food sources.
Residents are being urged to wash their hands often with soap and water. Hand sanitizer does not kill Cryptosporidium. Anyone with symptoms should stay home for at least 48 hours after diarrhea stops and avoid swimming pools for 14 days. People with weakened immune systems, such as those receiving cancer treatment, may face more severe illness.
Nationally, cryptosporidiosis surveillance shows an average of nearly two cases per 100,000 people each year since 2003. The Kingston outbreak, with 114 cases in a concentrated period, is a sharp departure from that norm. Anyone experiencing stomach illness is asked to contact Southeast Public Health for guidance.
