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As summer unfolds, the U.S. Centers for Disease Control and Prevention (CDC) has launched an investigation into a notable increase in cases of cyclosporiasis, a parasitic infection that causes severe watery diarrhoea. The state of Michigan has reported a significant spike in infections, with the CDC detailing that between May 1 and June 16, 145 cases were identified across 17 states, resulting in 20 hospitalisations. The affected individuals range in age from five to 86, raising concerns about the spread of this illness during peak season.
Michigan’s Alarming Outbreak
On July 1, the Michigan Department of Health and Human Services announced it is “actively investigating a large and growing outbreak of cyclosporiasis.” In just nine days leading up to the end of June, the state confirmed over 170 cases across several counties, including Monroe, Lenawee, and Wayne. This marks a stark rise compared to the typical annual average of approximately 50 cases reported in the state. The rapid increase has left public health officials scrambling to understand the source of this outbreak and mitigate further spread.
Understanding Cyclosporiasis
Cyclospora is a parasite responsible for causing intestinal illness, primarily contracted through the consumption of food or water contaminated with the organism. The Public Health Agency of Canada (PHAC) explains that the parasite often enters the water supply through faecal contamination from infected individuals. Once in the water, it can taint crops during irrigation or food processing, especially when sanitation measures such as hand washing and the use of gloves are neglected.
Diagnosing cyclosporiasis typically involves identifying oocysts—essentially the eggs of the parasite—in a stool sample. Treatment is achievable through prescribed medication, with symptoms generally subsiding within a few days of commencement. However, patients may experience lingering intestinal issues for weeks following treatment.
Symptoms and Timing
The onset of cyclosporiasis symptoms can be delayed, appearing anywhere from seven to 14 days after exposure. Common symptoms include:
– Watery diarrhoea
– Abdominal bloating and gas
– Fatigue
– Stomach cramps
– Loss of appetite
– Weight loss
– Mild fever
– Nausea
When left untreated, symptoms can persist for several weeks, often returning intermittently.
Global Context and Canadian Precautions
While cyclosporiasis can occur globally, it is particularly prevalent in tropical and subtropical regions such as Peru, India, and Mexico. In Canada, the PHAC reports no active investigations into outbreaks as of now, although historical data indicates an average of 238 cases reported annually from 2004 to 2019. A study published in September 2025 revealed a total of 5,337 cases between 2000 and 2022, with adults aged 30 to 59 disproportionately affected.
To mitigate the risk of infection, particularly for travellers to high-risk areas, the PHAC offers several recommendations:
– Avoid food washed in local water
– Drink water from safe sources
– Consume cooked food or fruit that can be peeled
Notably, some imported foods, including certain berries and lettuce varieties, have previously been associated with cyclospora outbreaks.
Why it Matters
The resurgence of cyclosporiasis during the summer months underscores the urgent need for enhanced public health measures and education regarding food safety. As international travel resumes and food imports rise, the potential for exposure to this parasite increases, particularly for vulnerable populations such as children, the elderly, and those with compromised immune systems. Awareness and proactive measures can help protect communities and prevent the spread of this often-overlooked but serious illness.
