The United States has closed the book on the cyclosporiasis outbreak that ran through its summer. The Centers for Disease Control and Prevention updated its investigation page on 11 September with a single flat sentence — “This outbreak has ended” — and a final count: 12,883 people made ill across 21 states, at least 570 of them admitted to hospital, and two deaths, both in Michigan. The illnesses began between 14 June and 17 August.
The agency’s own alert from the middle of the outbreak gives the sense of scale. On 14 July, when the CDC issued Health Alert Network notice 00531, it had 1,645 confirmed domestically acquired cases on its books and more than 5,100 more awaiting confirmation. By the same point a year earlier, the national count had been 249. Cyclospora cayetanensis is a single-celled parasite carried on food and in water rather than passed from person to person, which is why an outbreak of this kind traces back to a product rather than to a place.
It ended, on the CDC’s account, less because anything was switched off than because the vehicle ran out. Investigators traced the contamination to processed iceberg lettuce grown in central Mexico; the implicated lettuce was recalled on 17 July, and by September the affected products had passed their shelf life and were no longer in shops or restaurants. The Food and Drug Administration’s work on how the parasite entered the supply has not concluded.
What the CDC leaves the public with is the ordinary advice it gives every summer, and which this outbreak did not make redundant: wash hands and fresh produce thoroughly under running water before eating, cutting or cooking — and, because washing alone cannot guarantee the parasite’s removal, cook produce to 70°C when in doubt, since cooking kills it. Twelve thousand illnesses is a large number for a food-borne outbreak in a country with a well-instrumented surveillance system. It is also, now, a closed number.