Outbreaks caused by eating contaminated sprouts — “sproutbreaks” — have occurred every year in the United States since at least 1995. These episodes have taught us that sprouts are a risky food to eat.
Sprouts were found to be the cause of a devastating outbreak of Shiga toxin-producing E coli infections in Europe this summer. Ultimately, this outbreak caused more than 4,000 illnesses, more than 900 cases of hemolytic uremic syndrome, and 50 deaths.
Why are sprouts a risky food, you might ask? Some people think of them as the ultimate healthy food — fresh and natural. In fact, raw sprouts can be anything but safe. Lessons from outbreaks have taught us that it is a good idea for people who want to lower their risk for food poisoning to cook raw sprouts or avoid eating them raw.
Here is what we have learned:
Lesson 1: A sprouted seed is a perfect vehicle for pathogens.
A sprouting seed offers as inviting and nourishing an environment as bacteria like Salmonella or E coli could want–and the warm, moist conditions in which sprouts are produced only make matters worse. A single Salmonella organism on the outside of a seed can easily grow to an infectious dose after it has sprouted. The bacteria in or on growing sprouts cannot be washed off. Because even a low dose of Shiga toxin-producing E coli can make you sick, sprouts are a powerful vehicle for transmitting illness. Sprouts have also been the vehicle for Listeria, which causes a very dangerous infection for pregnant women and the elderly.
Lesson 2: Sprouts have caused many outbreaks of illness.
Since sprouts were first recognized as a source of food poisoning in the mid-1990s, they have become one of the “usual suspects” that foodborne disease epidemiologists look for when investigating an E coli or Salmonella outbreak. Since 1998, more than 30 outbreaks have been reported to the Centers for Disease Control and Prevention (CDC), due to many different kinds of sprouts — alfalfa, bean, clover, and others. In fact, CDC’s foodborne disease surveillance systems have identified three sprouts-associated outbreaks since June of 2010 that spread across multiple states.
Lesson 3: It is difficult to grow “safe” sprouts.
Once the potential dangers of sprouts became known, the U.S. Food and Drug Administration (FDA) developed guidance to help sprout growers reduce the risk of germs contaminating sprouts they produce and sell. Many sprouts growers now use practices to decontaminate seeds before sprouting, but no available method has proved completely effective. People who eat raw sprouts, including those who grow their own sprouts, ought to know that they are taking a risk, because contamination typically starts with the seed.
Lesson 4: Sprouts can make even young and healthy people ill.
This is one of the biggest lessons learned from the outbreak in Europe in 2011 and from our experience with outbreaks in this country. Sproutbreaks in the United States mainly affect healthy people aged 20-49 years. A typical victim may be an especially health conscious person in the prime of life. But illnesses from sprouts can be particularly severe in vulnerable populations, such as young children, older adults, pregnant women, and people with compromised immunity.
Lesson 5: It can be hard for those who become ill to remember having eaten sprouts.
We have found in our investigations that people often do not remember having eaten sprouts, because they are often just a garnish or one of many ingredients in a food dish. It is not necessary to eat large quantities of sprouts to get sick. An ill person’s inability to accurately recall what they ate sometimes makes it difficult to pinpoint an outbreak of sprouts.
For more information, visit these resources:
CDC Multistate Outbreaks Reports
By Lt. Cmdr. Rajal Mody, MD, MPH, U.S. Public Health Service, and originally posted Oct. 13, 2011 on the Keep Food Safe Blog.