Worldwide, at least 37 outbreaks of foodborne illnesses have been linked to sprouts between 1973 and 2005. In most instances, the illnesses were caused by either Escherichia coli (E. coli) O157:H7 or Salmonella bacteria.
Between 1996 and 2005, raw alfalfa sprouts and mung bean sprouts contaminated with Salmonella have been linked to a number of outbreaks in British Columbia, Quebec, Ontario, Saskatchewan and Alberta, as well as in the United States.
The largest outbreak linked to sprouts took place in Japan in 1996, when 6,000 people got sick and 17 died after eating radish sprouts contaminated with E. coli O157:H7. This type of bacteria was also implicated in outbreaks involving sprouted seeds in several U.S. states between 1997 and 2004.
How Sprouts Can Become Contaminated
Scientists believe that the most likely source of contamination is the seeds that are used to grow the sprouts. Seeds may become contaminated by animal manure in the field or during storage, and the conditions required to grow sprouts (e.g, warmth and humidity) are ideal for the rapid growth of bacteria. Poor hygienic practices in the production of sprouts have also caused some sprout-related outbreaks of foodborne illness in the past.
Most sprouts, including alfalfa sprouts, can only be eaten raw. This means they are not exposed to temperatures high enough to kill bacteria that may be present. Some sprouts, such as mung bean sprouts, can also be eaten cooked. To ensure that bacteria are destroyed, these sprouts should be cooked thoroughly. A recent outbreak of salmonellosis in Ontario in 2005 was linked to the consumption of raw and lightly-cooked mung bean sprouts, such as those found in some stir-fry dishes."