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Alert Date: 
Wednesday, July 19, 2017 - 12:00pm

July 19, 2017

Dear Health Care Provider,

Re: Cyclospora outbreak

Ontario is experiencing a large outbreak of Cyclospora infection. As of July 11, 2017, 52 locally-acquired cyclosporiasis cases have been reported in Ontario since May 1, which is substantially higher than the same time period in previous years. Additional cases continue to be reported. The purpose of this communication is to provide information about cyclosporiasis to support prompt diagnosis and treatment of infected patients.

  • Diagnosis: Cyclospora infection can be diagnosed by a stool ova and parasite (O&P) examination.
    If patients present with cyclosporiasis-compatible symptoms between now and the end of summer, please request a stool ova and parasite (O&P) on the lab requisition. It may be helpful on the lab requisition to also specify the request to rule out Cyclospora.
  • Treatment: First-line treatment of laboratory-confirmed Cyclospora is trimethoprim-sulfamethoxazole (TMP-SMX).

Additional information and resources on cyclosporiasis are provided below.

What is cyclosporiasis?

Cyclosporiasis is a gastrointestinal illness caused by infection with the parasite Cyclospora cayetanensis. It is commonly characterized by frequent watery diarrhea, as well as other symptoms such as anorexia, fatigue, abdominal cramps, nausea, and myalgia. Left untreated, symptoms typically last 6 to 7 weeks and can wax and wane in intensity. Symptoms typically improve within 2 to 3 days of starting trimethoprim-sulfamethoxazole (TMP-SMX), the first-line treatment for cyclosporiasis.

How is Cyclospora infection acquired?

People are infected by ingesting food or water infected with the parasite. As Cyclospora is not endemic in Canada, most reported cases in Ontario are infected when visiting an endemic country (e.g., countries in the Caribbean, South and Central America, South and South East Asia). However, when cases occur in individuals who did not travel, an investigation is launched. Most outbreaks in Ontario occur in the spring and summer and outbreaks of locally-acquired infections have been related to produce such as berries or herbs imported from Cyclospora endemic countries. The infection is unlikely to spread from person to person.

Additional resources on cyclosporiasis

For more details on Cyclospora infection, see: Cyclospora Information for Health Professionals.

For more information on cyclosporiasis in Ontario, including links to testing information, see:


Dr. Wajid Ahmed, MBBS, MAS, MSc, FRCPC

Acting Medical Officer of Health