EM Field Card · Foodborne

Cyclospora cayetanensis

Parasitic diarrheal illness. Fecal-oral via contaminated fresh produce or water. Not spread person to person. Seasonal in the US, May through August.

Updated Jul 2026 Status Active multistate surge Read time 60 sec
1,645
confirmed US cases since May 1
5,100+
additional under review
34
states reporting
9%
hospitalized · 0 deaths
Why now

Epidemiology

Case counts are running far above baseline. 1,645 confirmed vs 249 at the same point in 2025. Michigan is the largest cluster.

No single food source confirmed yet. FDA investigation ongoing. Historical culprits: raspberries, basil, cilantro, snow peas, lettuce, salad mixes.

Washing does not reliably remove it. Cooking to 158 F kills it.

Recognize it

Typical presentation

  • Watery diarrhea, frequent, often explosive
  • Marked anorexia and weight loss
  • Bloating, gas, cramping, nausea, fatigue
  • Low-grade fever and vomiting are less common
  • Relapsing-remitting waves are the classic clue
The discriminator

Incubation window

Day 2Day 7Day 14+

Symptoms start about a week after exposure, range 2 to 14 days. If diarrhea began within hours of a meal, it is not Cyclospora. That gap separates it from bacterial food poisoning.

Clinical Pearl

You have to ask for the test.

Routine stool O&P misses Cyclospora. Specifically order Cyclospora testing (ova & parasite with acid-fast or modified stains, or GI PCR panel that includes it).

Shedding is intermittent. A single negative does not rule it out. Send multiple samples if suspicion is high.

Treat it

Treatment

TMP-SMX DS (160/800)
1 tab PO BID × 7–10 days
  • First line for immunocompetent adults and children over 2 months
  • Immunocompromised: longer course, ID input
  • Sulfa allergy: limited alternatives, involve ID
  • Supportive: hydration, electrolytes
Escalate

Alarm signs

  • Cannot tolerate PO, ongoing volume loss
  • Clinical dehydration or electrolyte derangement
  • Significant or rapid weight loss
  • Prolonged or worsening course despite treatment
  • Immunocompromised with severe illness → admit, IV fluids
Watch closely

High-yield populations

  • Immunocompromised (HIV/AIDS, transplant, chemo): prolonged, severe, relapsing
  • Travelers to tropical or subtropical regions
  • Very young and elderly: dehydration risk
  • Anyone with prolonged watery diarrhea in summer or fall plus fresh produce exposure
Set expectations

Course & anticipatory guidance

  • Treated: improves within a few days of starting Bactrim
  • Untreated: days to a month or longer, comes and goes in waves
  • Reinfection is possible. No lasting immunity
  • Return for inability to keep fluids down, lightheadedness, or worsening after day 3 of treatment
Sources: CDC Health Alert Network notice and Cyclosporiasis Surveillance, July 2026. Numbers evolve, confirm current counts and dosing against CDC guidance. For clinician education only, not a substitute for clinical judgment.
@BloodSweatxED · Emergency Medicine · Chalk Talk No. 001 · Human curated, AI generated · ← Back to the deck