CIDRAP Op-Ed: The Cyclospora outbreak was, and still is, a communications failure | CIDRAP

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CIDRAP Op-Ed: The Cyclospora outbreak was, and still is, a communications failure

Jess Steier, DrPh

Cyclospora

Foodborne Disease

Public Health

Water Alternatives / Flickr cc

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The response to the current large outbreak of food-related illnesses caused by a microscopic parasite is a communications failure, not a failure of the investigation.<br>A few characteristics of Cyclospora make it tricky to chase down. Because it will not grow in culture, the standard playbook doesn't apply. With most foodborne bacteria, a lab grows the organism, sequences it, and uploads the genetic fingerprint to PulseNet, the national network that flags when a case in one state matches a case in another.<br>The US Centers for Disease Control and Prevention (CDC) has instead been working from partial genotyping, because Cyclospora's genome is complicated enough to defeat the sequencing methods that work for bacteria. Cyclospora contamination on produce is often sparse and unevenly distributed, and it tends to sit close to the limit of what a test can detect, which is how contaminated lettuce ends up testing clean. Investigators were left with the oldest tools in the kit: interviews and shipping records.<br>Important early clues widely missed<br>Dr. Mike Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy (which, of course, publishes my CIDRAP Op-Eds), taught me that when cases start rolling in, the demographics of who is getting sick can hand you an important early clue. These cases skewed heavily toward adults, with the CDC putting the median age at 44 across a range from 1 to 89 years, and the relative absence of young children pointed toward something green rather than something fruit.<br>If you have young kids you know exactly why. They are devoted fruit eaters. (I used to joke that my daughter was going to turn into a strawberry.) But more spotty toward veggies.<br>That narrows things, but the hunt continues. There are other important factors, too, like understanding how a growing region is organized into blocks, when each produce item was cut and by whom, how product from different fields gets combined at a processor, how long it takes to move from a field in central Mexico to a restaurant in Michigan, and how fast a perishable product cycles off the shelf.<br>That knowledge does more than point at a culprit. It also helps estimate how many people could have been exposed and where. It tells you when contaminated products should have cleared the shelves and new exposures should stop, even though reported counts will keep climbing for weeks afterward. Because molecular typing cannot deliver the clean fingerprint that is available in a bacterial outbreak, it is also central to deciding whether a case in one state belongs with a case in another. Trace-back is a supply chain exercise as much as an epidemiologic one.<br>Michigan went through ingredient-level food histories from 190 people who had eaten at Taco Bell before falling ill, and 90% of them had eaten iceberg lettuce. The FDA's trace-back investigation followed the paper backward, converging on one supplier and then on a single independent farm in central Mexico that Taylor Farms says accounts for less than 1% of the US iceberg supply. The recall came July 17.<br>9 states in the outbreak, but 41 affected overall<br>This is the largest documented Cyclospora outbreak in US history, and the coverage has that part right. What has reached the public is a scary number that keeps going up.<br>It misses the fact that, while cyclosporiasis—which is what a Cyclospora infection is called—has now been reported in 41 states, the outbreak is only in nine. The numbers being reported measure different things. The CDC and Food and Drug Administration (FDA) have included 1,947 confirmed cases in the nine-state Taco Bell outbreak, which epidemiologic and trace-back evidence links to iceberg lettuce, while the CDC separately reports more than 4,000 confirmed domestically acquired cases nationally since May.<br>In addition, thousands of samples from patients are still awaiting CDC confirmation, plus several hundred more in travelers who got sick abroad. Some states count probable and confirmed cases together, so their totals run higher still. Stack all of it, as plenty of coverage has, and you get a single national outbreak that doesn't exist.<br>Consider what happened when the CDC added four states to the outbreak on July 24. It read as though the outbreak had spread, but investigators think those patients may have gotten sick around the same time as the patients in the original five states, and simply took longer to connect to the same source.<br>Stack all of it, as plenty of coverage has, and you get a single national outbreak that doesn't exist.

Cyclosporiasis turns up somewhere every summer, following a seasonal...