Cyclosporiasis in 2026: A clinical update for pediatricians

An active, multistate cyclosporiasis outbreak is underway this summer, and pediatric providers should have a low threshold to consider Cyclospora cayetanensis in children presenting with protracted or relapsing watery diarrhea — particularly during the current outbreak season.¹

Current epidemiology

Per CDC surveillance data, the agency received reports of 1,645 domestically acquired cyclosporiasis cases among people with illness onset from May 1 through July 13, 2026. Of these, 141 were hospitalized and no deaths have been reported. Cases have been reported across 34 states. Patients ranged from 2 to 95 years of age (median 44), 56% were female, and median illness onset was June 22, 2026 (range from May 1 to July 9).^1,2

Local, state, and federal public health authorities, including CDC and FDA, are investigating several clusters spanning more than one state, with source investigations ongoing. A parallel cohort of 440 travel-associated cases underscores that recent international travel remains an important element of the exposure history, independent of the domestic outbreak.

CDC and state/federal regulatory partners monitor cases year-round to detect outbreaks linked to a common food source, and case counts characteristically rise during spring and summer, with the cyclosporiasis season generally spanning May 1 through August 31 — this outbreak falls squarely within that window.

Reporting obligations

Cyclosporiasis is a nationally notifiable disease and is reportable in 47 states, the District of Columbia, and New York City. Even in jurisdictions where it is not formally reportable, clinicians are encouraged to notify local health departments of suspected cases and clusters to support outbreak detection. Confirmed cases should be reported to the local health department per standard notifiable disease protocols.

Clinical presentation and why it's easily missed

Unlike most acute infectious diarrheal illnesses that resolve within days, cyclosporiasis characteristically produces a protracted or relapsing course. Robert W. Frenck Jr., MD, FAAP, chair of the AAP Section on Infectious Diseases, notes that the diagnostic clue distinguishing it from typical viral gastroenteritis is exactly this pattern: watery diarrhea, bloating, and fatigue lasting weeks, sometimes with a remitting-relapsing course in which symptoms appear to resolve and then recur.²

Associated findings can include anorexia, nausea, cramping, bloating, flatulence, fatigue, unintended weight loss, low-grade fever, vomiting, headache, and myalgias. Incubation is typically about one week post-exposure but can range from 2 days to 2+ weeks, which frequently complicates exposure-source recall. Asymptomatic infection occurs and still permits oocyst shedding, which has implications for community transmission even in the absence of clinical illness.

Differential and diagnostic considerations

Consider Cyclospora in the differential for:

• Diarrhea persisting beyond the typical 5–7 day course of viral gastroenteritis
• Relapsing/remitting GI symptoms
• Recent consumption of fresh produce (berries, leafy greens, herbs such as basil/cilantro) or unsafe water
• Recent travel to Cyclospora-endemic regions
• Immunocompromised patients with prolonged diarrhea

Diagnosis requires stool testing; oocyst shedding can be intermittent, so a single negative sample does not rule out infection, and repeat sampling may be warranted when clinical suspicion is high. Modified acid-fast staining and UV autofluorescence microscopy remain classic methods, but many labs now use multiplex molecular (PCR-based) GI pathogen panels, which improve sensitivity and can simultaneously screen for other causes of infectious diarrhea in the differential.

Treatment

First-line therapy is trimethoprim-sulfamethoxazole (TMP-SMX), typically for 7–10 days; immunocompromised patients may require an extended course. For patients with sulfa allergy or intolerance, alternative regimens are limited and less well-established — consult current CDC clinical guidance and consider infectious disease consultation for these cases. Supportive care with oral or IV rehydration should be addressed alongside antimicrobial therapy, particularly given the potential for prolonged fluid losses.

Populations at higher risk for severe or prolonged disease

Immunocompromised pediatric patients — including those with malignancy, solid organ transplant, or on immunosuppressive therapy — are at risk for more severe, prolonged, or relapsing disease and warrant closer follow-up and consideration of extended treatment courses.

Counseling points for families

• The parasite is not directly person-to-person transmissible; excreted oocysts require 1–2 weeks in the environment to become infectious, after which they can contaminate food or water sources.
• Routine produce washing reduces but does not eliminate risk, since oocysts adhere tenaciously to produce surfaces.
• No vaccine or chemoprophylaxis exists; prevention counseling should emphasize hand hygiene, produce rinsing, and safe water sourcing, especially for travel.

Bottom line for practice

Given the current outbreak intensity and the seasonal timing, maintain a heightened index of suspicion for Cyclospora in any child with watery diarrhea persisting beyond a week or following a remitting-relapsing pattern, obtain stool testing (with repeat sampling as needed), initiate TMP-SMX when confirmed, and report suspected and confirmed cases to your local health department to support ongoing multistate outbreak investigations.

References

1. Centers for Disease Control and Prevention. Surveillance of cyclosporiasis. CDC. Updated June 18, 2026. Accessed July 15, 2026. https://www.cdc.gov/cyclosporiasis/php/surveillance/index.html

2. Frenck RW Jr. Cyclosporiasis in children: symptoms, treatment & prevention. HealthyChildren.org. American Academy of Pediatrics. July 10, 2026. Accessed July 15, 2026. https://www.healthychildren.org/English/health-issues/conditions/infections/Pages/cyclosporiasis-in-children-symptoms-treatment-and-prevention.aspx