Every year, one in six Americans is sickened by contaminated food. There is a seemingly endless stream of national outbreaks; in the past few months alone, we've seen a salmonella outbreak linked to imported cucumbers, closely followed by an outbreak of listeria in soft cheeses, and the recent E. Coli outbreak in Chipotle restaurants in Washington and Oregon. These headline-grabbing multi-state outbreaks account for only 11 percent of all foodborne illnesses, but are responsible for 34 percent of hospitalizations and more than half of associated deaths each year. Of the 48 million people affected annually, there will be roughly 128,000 hospitalizations and 3,000 deaths from foodborne bacteria like listeria, salmonella, and E. coli.
A recent Centers for Disease Control report found that the number of multi-state foodborne disease outbreaks are on the rise, currently averaging around two per month. These outbreaks are seemingly bigger, more frequent, and deadlier than before. The reality is not quite that simple.
What qualifies as an outbreak?
According to the CDC, a foodborne disease outbreak is defined as "when two or more people get the same illness and investigation shows it came from the same contaminated food or drink." This can mean anything from contaminated vegetables at a family potluck to the recent incidents of contaminated tomatoes at Chipotle, which sickened more than 40 people in Oregon and Washington.
Multi-state foodborne illness outbreaks represent just three percent of all reported outbreaks in the U.S., but account for 56 percent of foodborne illness deaths.
Local, single-state outbreaks are most likely to be caused by the comparatively mild norovirus, which presents with what many consider the classic signs of food poisoning: diarrhea, vomiting, and stomach pain. Ninety-one percent of multi-state outbreaks are caused by the more serious pathogens salmonella, listeria, and E. coli, bacteria that can cause severe disease and death. Multi-state foodborne disease outbreaks represent just three percent of all reported outbreaks in the U.S., but account for 56 percent of all foodborne illness deaths.
In 2015, salmonella, listeria, and E. coli were responsible for eight of the nine multi-state outbreaks. The CDC report covering outbreaks from 2010 to 2014 identified salmonella as the cause of the greatest number of illnesses and hospitalizations, responsible for a full 82 percent of cases and the three largest outbreaks over the four-year period (attributed to eggs, chicken, and ground tuna). Listeria, a bacteria that is particularly dangerous for pregnant women, the elderly, and the immunocompromised, was responsible for 86 percent of deaths, more than half of which were related to a single 2011 outbreak linked to cantaloupe.
When an outbreak occurs, it is first investigated by the local and state health departments. They identify the source of the outbreak through interviews and laboratory testing, taking any additional steps necessary to control it. Foodborne illness is a "notifiable condition," which means local health departments are responsible for reporting confirmed outbreaks to the CDC within seven days. The CDC maintains a shared database — PulseNet — that allows investigators to compare the DNA fingerprint of the bacteria from a specific patient with strains identified in other infected individuals the national other patients. If the two are a match, they can quickly identify outbreaks that may otherwise have gone unnoticed.
Through DNA tracking, what would otherwise appear to be isolated groups of sickened individuals may be revealed as originating from a single source. Investigators will then try to identify the common product involved to pinpoint the place of contamination. This is not always possible — Chipotle restaurants in the PNW are reopening this week after a thorough cleaning, despite the fact that officials have still not identified the source of the recent outbreak. In other cases, DNA testing can lead investigators to solve years-old cases of foodborne illness — as demonstrated by the recent listeria outbreak traced back to Blue Bell Creameries. Infected patients as far back as 2010 were connected to the present-day outbreak through the PulseNet database.
Identifying a source and treating the infected are important steps in protecting public health, but the ideal situation is to stop outbreaks from happening in the first place. That's the role of the Food and Drug Administration (FDA) and the US Department of Agriculture (USDA), the government agencies in charge of protecting our food. The recent CDC reports suggests they are failing.
Why do outbreaks occur?
That depends on the case. We know how food is contaminated and, in most cases, how that contamination can be prevented. The majority of outbreaks can be traced back to a failure to observe safe food practices — practices that should be enforced by the FDA and USDA.
In the case of the cantaloupe outbreak, the deadliest foodborne illness outbreak since 1985, infections in 28 states were traced back to a single farm in Colorado. The cause of the outbreak was the presence of listeria bacteria, but the food was contaminated due to a lack of federally standardized food safety regulations and a failed monitoring system. Less than a week before the outbreak, the farm received a food safety score of 96 (out of 100) in an audit by an outside contractor. Investigators later identified listeria in multiple locations, including on a conveyor belt, in standing water around the farm, in a melon drying area, and on corroded farming equipment. Shortly after the outbreak, Robert Stovicek, the head of the involved auditing company, was asked how the farm could have received such high marks. He attributed it to "variations as to how people interpret unsanitary conditions." In reality, there should be no variation; unsanitary food conditions should be absolutes. The lack of oversight from the FDA, which requires no regular testing from manufacturers, plays a significant role in allowing cases such as these to slip through the cracks.
The listeria outbreak at Blue Bell Creameries earlier this year was similarly connected to a lack of oversight. Originally thought to be a result of contamination at one Oklahoma plant, further sampling identified listeria at additional plants in Texas. The FDA ultimately found that the company had failed to observe basic food safety practices and that Blue Bell had discovered listeria in the same facility two years before the national outbreak —but failed to address the problem.
Are known outbreaks on the rise?
Yes. Between 2010 and 2014, there were a total of 120 outbreaks — for an average of 24 each year — involving anywhere between two and 37 states. Compared to the 79 identified outbreaks between 2005 and 2009 and 51 outbreaks between 2000 and 2004, there's been a definite upward trend in the number of outbreaks nationwide. And these numbers only reference reported cases — they do not include people who self-misdiagnose or decide to tough it out without contacting a health care professional. The CDC estimates that for every one case identified, there are more than 20 that go by undiagnosed.
Because our food today is globally distributed, a single source of infection can quickly spread to multiple areas of the country. The CDC explains that "increasing integration and consolidation of agriculture and food production can result in a contaminated food rapidly causing a geographically widespread outbreak." As the American agriculture industry shifts from small independent farms to larger corporate ones, a greater proportion of food products share a single source. Contamination can quickly spread across multiple states when one affected location supplies hundreds of outlets across the country .
It is particularly disconcerting that outbreaks caused by antibiotic resistant bacteria are on the rise. In a test of 10 people sickened by salmonella-contaminated pork this August, 100 percent of patients carried multi-drug resistant bacteria. Sub-therapeutic levels of human antibiotics have been used to induce rapid growth in livestock for almost half a century. Over time, this practice has helped to cause our alarmingly high rates of antibiotic resistant bacteria. These bacteria are introduced to our food supply, increasing the potential for more difficult to treat outbreaks.
"Americans shouldn’t have to worry about getting sick from the food they eat."
The outbreak of salmonella earlier this year that was traced back to imported cucumbers from Mexico exposes another reason for the increase in outbreaks: the US imports almost 20 percent of its food, from countries with food safety standards that may differ widely from our own. The more steps between farm and table, the more difficult it is to prevent contamination. Consumer pressure to eliminate preservatives from foods are another possible explanation. Those preservatives help food last longer but they may also inhibit bacterial growth, adding a layer of protection.
As the number of foodborne illness outbreaks has increased, so has the media coverage. The CDC report reflects what we've seen in the news — outbreaks are a large and seemingly constant threat. But this heightened awareness may not reflect legitimate changes in our food safety. There may be more outbreaks happening, but it is equally possible that the improved methods for investigating outbreaks have simply increased our ability to identify them. There were only 34 outbreaks identified between 1995 and 1999, but those numbers predate the widespread use of PulseNet, CDC's nationwide bacterial DNA database, which was first launched in 1996.
Regardless of whether the number of outbreaks is genuinely increasing, or the numbers are merely an artifact of improved technologies, the fact remains that they are happening far too often. As CDC director Dr. Tom Frieden succinctly put it, "Americans shouldn't have to worry about getting sick from the food they eat."
What is the FDA doing about this?
According to Jason Strachman Miller, an FDA spokesman, the agency has recognized that they must be proactive in protecting food safety rather than simply reacting to outbreaks as they happen. "New preventive controls rule issued this September require food manufacturers to identify potential hazards in food and take steps to prevent those hazards," Miller says. With imported foods responsible for 18 of the documented outbreaks between 2010 and 2014, "for the first time, importers will have an explicit responsibility to verify that their foreign suppliers have adequate preventive controls in place to ensure that the food they produce is safe."
These rules are promising, although it is shocking that basic concepts like verifying international suppliers' food safety measures are only just now being implemented. But, as with many reforms to large industries, it's unclear how these rules will actually impact food safety. FSMA, "the most sweeping reform of our food safety laws in more than 70 years," had no apparent impact, but it's possible that the rules released this year will have a greater influence on the food industry.