August 4, 2026 Author : Saraiva da Cunha (infectious diseases ) Cyclosporiasis is an intestinal parasitic infection caused by the protozoan Cyclospora cayetanensis , the only Cyclospora species capable of infecting humans. The parasite was named in honor of Cayetano Heredia University in Lima, Peru, where the first investigations were carried out. Cyclosporiasis occurs mainly in tropical and subtropical regions where the parasite is endemic, and in areas with poor sanitation conditions and hygiene practices. Infection occurs after consuming food or water contaminated with Cyclospora cayetanensis. It causes diarrhea and other symptoms and may require medical treatment. In some European countries, cases of cyclosporiasis have been identified in travelers returning from endemic areas and, more rarely, in people with no travel history. In the United States, a large outbreak of cyclosporiasis is ongoing in 2026 and has been linked to the consumption of lettuce imported from Mexico. For travelers, prevention consists of following the standard traveler’s diarrhea prevention measures . Causes and transmission of cyclosporiasis Cyclosporiasis is an intestinal parasitic infection transmitted through contaminated food or beverages. Transmission occurs via the oral route, through the consumption of food or water contaminated with Cyclospora cayetanensis . Cyclospora cayetanensis is shed in the feces of infected individuals. Poor sanitation conditions and inadequate hygiene practices can lead to contamination of water and food with fecal residues. Depending on the type of food, contamination may occur during production, processing, distribution, storage, or handling before consumption. Fresh raw produce, such as fruits and vegetables, is most commonly involved. Direct person-to-person transmission does not occur . One reason is that the forms of the parasite shed in feces must spend some time in the environment and complete a maturation process (sporulation) before they become infectious. Only sporulated oocysts are capable of causing infection. Symptoms of cyclosporiasis The incubation period (the time between infection and the appearance of symptoms) of cyclosporiasis is about one week , although it may range from two days to more than two weeks. The main symptom is profuse watery diarrhea. Other symptoms vary but may include: Lack of appetite Weight loss Abdominal cramps and bloating (gas) Nausea and vomiting Headaches and muscle pain Other nonspecific symptoms When left untreated, symptoms may resolve within a few days, but they can also persist for more than a month or recur intermittently. The illness may be more prolonged and debilitating in children, older adults, and people with severe chronic diseases or weakened immune systems , such as individuals living with human immunodeficiency virus (HIV) infection. Some infected individuals, particularly in areas where the parasite is endemic, may remain asymptomatic. Diagnosis and treatment A definitive diagnosis of cyclosporiasis requires stool testing to identify the parasite . Multiple stool samples collected over several days are often necessary because shedding of the parasite may be intermittent. Molecular biology techniques are increasingly being used for diagnosis. Treatment consists of specific antimicrobial drugs , most commonly a combination of trimethoprim and a sulfonamide, together with supportive measures, particularly maintaining adequate hydration to compensate for fluid losses caused by diarrhea. Prevention of cyclosporiasis Since no vaccine is available, the main preventive measures are: Do not consume food or water that may have been contaminated with fecal matter. Strictly follow hygiene measures when handling food, both by professionals involved in the different stages of the food production chain and by consumers when purchasing, transporting, and preparing food for consumption. Although it is not among the most common causes, Cyclospora cayetanensis is one of the microorganisms that can cause traveler’s diarrhea . Therefore, travelers to endemic areas should follow the recommendations for traveler diarrhea prevention . Sources Autoridade de Segurança Alimentar e Económica. Cyclospora . Centers for Disease Control and Prevention. About cyclosporiasis . 2026. Mathison BA, Pritt BS. Cyclosporiasis-updates on clinical presentation, pathology, clinical diagnosis, and treatment. microorganisms . 2021;9:1863. Meet the infectious diseases clinical team from Hospital da Luz network. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item. English translation generated with AI and reviewed by the editorial team
