Missouri's Cyclospora Outbreak Nears 2,000 Cases as Federal Investigators Track Outbreaks With No Known Source

New federal data show cyclosporiasis cases in the United States have surged past 14,000 since May, more than ten times last year's total for the same months, and health investigators still cannot identify what is causing several of the outbreaks feeding that number.

A State Outbreak Still Climbing

Missouri health officials reported 1,950 confirmed cyclosporiasis cases as of Sunday, a 24 percent increase from the week before.

The Missouri Department of Health and Senior Services said many of the state's cases are part of the outbreak linked to iceberg lettuce grown in central Mexico, which food company Taylor Farms recalled on July 17 after epidemiologic and traceback data connected the lettuce to the illnesses.

Officials have also been clear that not every Missouri case has been tied to that outbreak, meaning some infections in the state are part of the wider, still unresolved picture.

Missouri typically records only about a dozen cyclospora cases in an entire year. This year's total is already well over a hundred times that.

One Confirmed Source, Several Open Cases

The Centers for Disease Control and Prevention reported nearly 14,000 domestically acquired cyclospora cases nationwide since May 1, compared with roughly 1,180 cases over the same stretch last year.

Of this year's cases, 9,481 fall within the outbreak tied to the recalled lettuce, which now spans 17 states after Maine and Massachusetts were added earlier this month.

That outbreak has caused at least 398 hospitalizations and two deaths, both in Michigan patients who had underlying health conditions, according to the CDC.

Beyond that outbreak, the Food and Drug Administration is tracking seven separate active cyclospora investigations.

Only the lettuce outbreak has a confirmed source. Two of the others have grown in recent weeks, including one that climbed from 115 cases to 172.

The FDA said traceback work is continuing on the outbreaks that remain unresolved.

Why the Source Is So Hard to Pin Down

Cyclospora is a microscopic parasite that spreads through contaminated food or water, most often fresh produce.

Public health investigators say tracing it back to a specific farm or shipment is difficult in part because standard tests do not always catch the small amounts of the parasite that can still make someone sick.

The CDC also notes that many infected people recover without seeking medical care and are never tested, and confirming whether a case belongs to a specific outbreak can take up to six weeks, delaying the full picture.

That lag is one reason officials expect confirmed case counts, in Missouri and nationally, to keep climbing even after new infections slow.

It is also why some outbreaks each year are never traced to a specific food at all.

What This Means Going Forward

Doctors treating patients in Missouri told local reporters there are early signs the state's outbreak may be nearing its peak, based on the recent pace of new cases.

That is a hopeful signal, but it does not close the investigation. State and federal officials are still working through the cases not yet linked to the lettuce recall, and the FDA's separate, unexplained outbreaks remain open.

For now, the confirmed source of the largest share of this year's cyclospora cases is the recalled lettuce, and that recall has been in effect for a month. The cases still without an answer are the ones investigators are watching most closely.