In late February, the U.S. Centers for Disease Control and Prevention (CDC) released a detailed report describing a summer 2014 outbreak of Salmonella linked to cucumbers grown in the Delmarva region of Maryland. The outbreak resulted in 275 confirmed illnesses and the death of one man. Considering that CDC estimates only one in 30 Salmonella cases are confirmed, the outbreak is believed to have had a wide-reaching impact on consumers. Given the size of this Salmonella outbreak, some consumers were surprised and even alarmed to first hear about it several months after it ended. Why did CDC not previously alert the public, as they do with many other foodborne illness outbreaks? The answer to that question comes down to whether or not health officials at CDC believe they can release information that will protect public health and prevent illnesses. The incident highlights many of the challenges of investigating outbreaks caused by fresh produce, said Matthew Wise, the outbreak response team lead in CDC’s Division of Foodborne, Waterborne and Environmental Diseases. Unfortunately, Wise told Food Safety News, investigators felt that, in this case, they determined the source too late to help the public. Outbreak investigations always require a balancing act between wanting to work as quickly as possible and wanting to be absolutely sure you’ve found the right source, he noted. When outbreaks involve fresh produce, the timeline for finding the source and alerting the public is significantly shortened. For one thing, cucumbers are a short shelf-life product, typically lasting no more than two weeks. Once the growing season ends, there isn’t much time for the product to continue sitting in stores or refrigerators to pose a risk to consumers. Because of that, investigators were hard-pressed for time to figure out what was going on, Wise said. The cucumber outbreak began picking up steam in early July and peaked on July 30. Yet, at that point, no one knew an outbreak was occurring. It wasn’t until mid- to late-August that CDC and state health officials started piecing together the outbreak that seemed to be impacting a large number of people who lived in, or traveled near, the Delmarva region, based on data from PulseNet, CDC’s national disease database. The first suspect was tomatoes. The genetic fingerprint of the Salmonella outbreak strain matched one associated with numerous outbreaks and hundreds of illnesses caused by tomatoes grown in the region between 2002 and 2010. It wasn’t until September that investigators shifted their focus from tomatoes to cucumbers, a product associated much less frequently with Salmonella. On Sept. 11, 2014, CDC and U.S. Food and Drug Administration (FDA) had a meeting with produce industry trade associations to present their data and get feedback on their hypothesis that the outbreak was coming from cucumbers. Wise said that the idea to host consultation meetings with industry was an idea recently proposed by The Pew Charitable Trusts. In late September, the agency was finally confident that it had traced the cucumbers back to a single farm. The outbreak had significantly tapered off, with the last illness appearing on Sept. 30. By then, Wise said, there wasn’t much use in sending out an alert. “We’re constantly discussing our decision to notify the public with an outbreak posting, from the day we detect the cluster to the day we close the investigation,” he said. “Our general principle is to communicate with the public when we have something concrete and specific — information that can reduce consumer risk.” CDC recently made the call to notify the public about the risk of Listeria associated with certain caramel apples before they could confirm the exact producer involved. But that was because the caramel apple outbreak had already caused at least five deaths and dozens of serious hospitalizations, and caramel apples have a long shelf life, Wise explained. Also, it’s likely the agency hasn’t forgotten a 2008 Salmonella outbreak ultimately linked to jalapeño peppers. At the time, the incident was the largest Salmonella outbreak in almost 30 years, with more than 1,300 confirmed illnesses. At first, health officials declared tomatoes as the source. By the time they rescinded that declaration and pointed to jalapeños as the real cause, members of the produce industry had sharply criticized investigators for wrongfully damaging tomato sales. With the history of Salmonella outbreaks caused by tomatoes grown in the Delmarva region, Wise said that it would have been easy to assume tomatoes were also responsible for the summer 2014 outbreak. “Even if we go into an investigation with ideas about the usual suspects, we have to make sure we ask patients about a wide range of exposures to make sure we don’t miss something new,” he said.