Epidemiological investigation of a large trichinellosis outbreak in Lebanon, October 2023-February 2024.

On 4 December 2023, trichinellosis cases were notified in Jahliyeh, Mount Lebanon. We investigated to determine the source, magnitude, and control measures. We defined a suspected case as a Jahliyeh resident with ≥1 compatible symptom diagnosed by a physician after 1 October 2023; a probable case as having ≥3 typical symptoms (fever, myalgia, edema, or eosinophilia); and a confirmed case as a suspected or probable case with laboratory confirmation by muscle biopsy or serology. We surveyed reachable households (252/561) to identify cases and assess meat consumption practices, inspected local butcheries, and tested meat samples. We identified 290 cases: 268 (92%) suspected, 21 (7.2%) probable, and 1 (0.3%) confirmed. Median age was 35 years (range 2-85); 34% required hospitalization. Illness was associated with Butchery A meat (risk ratio [RR] = 8.2; 95% confidence interval [CI]: 5.6-12.1) and uncooked meat (RR = 1.9; 95% CI: 1.4-2.6), while freezing and cooking were protective. Food inspection revealed major hygiene breaches at Butchery A and Trichinella larvae in minced beef and sausage. This outbreak was epidemiologically confirmed despite limited laboratory confirmation in humans. We recommend strengthening food safety inspections, intersectoral One Health collaboration, laboratory capacity, and public awareness of safe meat preparation.