There have been many instances around the world of people getting sick from sprouts. The problem is that sprouts come from seeds that come from farms. Farms tend to have animals on them and animals (even healthy animals) often carry Salmonella or E.coli O157:H7. Just a small amount of contamination can contaminate a huge amount of seed because seed is processed in bulk. Even a very low level of contamination with Salmonella or E. coli O157:H7 can cause problems because these two pathogens can multiply under the condition used for sprouting the seeds.
Here is a report from the American CDC on disease outbreaks associated with sprouts along with the Editorial Note from the report:
“7 Outbreaks of Escherichia coli O157:H7 Infection Associated with Eating Alfalfa Sprouts – Michigan and Virginia, June-July 1997 MMWR Vol 46, No 32;741
(http://www.cdc.gov/mmwr/PDF/wk/mm4632.pdf)
Summary: In June and July 1997, simultaneous outbreaks of Escherichia coli O157:H7 infection in Michigan and Virginia were independently associated with eating alfalfa sprouts grown from the same seed lot. The outbreak strains in Michigan and Virginia were indist…”
"Editorial Note: These are the first reported outbreaks of E. coli O157:H7 infection associated with eating alfalfa sprouts. Since 1995, four outbreaks of Salmonella infection have occurred in the United States because of consumption of contaminated alfalfa sprouts (1,2; CDC, unpublished data, 1997). In 1996 in Japan, radish sprouts were associated with the largest recorded outbreak of E. coli O157:H7 infection, in which approximately 6000 cases occurred (3).
"As in previous alfalfa sprout-associated outbreaks of infection with Salmonella serotype Stanley (1) and Salmonella serotype Newport (2), the Michigan and Virginia outbreaks of E. coli O157:H7 infection probably were caused by contaminated alfalfa seeds, rather than contamination ring the sprouting process. Because alfalfa seeds are a raw agricultural commodity, they can become contaminated with animal feces that may harbor pathogens such as Salmonella or E. coli O157:H7 during growth, harvest, processing, storage, shipping, or sprouting. The recurrent implication of alfalfa sprouts as a vehicle for foodborne illness highlights the need for strengthened prevention and control measures to ensure the safety of this product. Studies of alfalfa seed inoculated with low numbers of Salmonella suggest that the number of organisms present on seeds may increase up to 10,000-fold during the sprouting process (4). The effect of the sprouting process on the growth of E. coli O157:H7 is unknown. In April 1996, representatives of the sprout industry met with the Food and Drug Administration (FDA) and CDC to discuss research needs to identify effective methods of alfalfa seed decontamination. However, research has not identified such a method; treatments, such as soaking seeds in water with chlorine concentrations of 2000 ppm (the highest allowable concentration), reduce the level of contamination but can leave viable microorganisms that may then be amplified during the sprouting process (4). Further efforts are needed to evaluate seed and sprout disinfection strategies.
"In addition to seed decontamination, prevention of future alfalfa sprout-related outbreaks will depend on identification of critical control points to reduce the likelihood of contamination during seed production and distribution. Additional prevention approaches could include categorizing sprout growers as food service workers rather than agricultural harvesters, along with systematic inspection and certification of sprouting facilities. As with all fresh produce, consumers should thoroughly rinse alfalfa sprouts before eating; however, the effectiveness of rinsing to reduce contamination is unknown. Persons at higher risk for severe complications of E. coli O157:H7 or Salmonella infection, such as infants and young children, the elderly, pregnant women, or immunocompromised persons, can reduce their risk by not eating raw alfalfa sprouts.
“The Michigan and Virginia E. coli O157:H7 outbreaks demonstrate the value of molecular subtyping in the investigation of foodborne outbreaks. In both states, an
increase in the number of reported cases of E. coli O157:H7 infection was suggested by PFGE analysis to be a common-source outbreak rather than an increase in sporadic cases. In addition, molecular subtyping of isolates from both states by PFGE and phage typing at CDC demonstrated that these outbreaks were linked by a common strain, corroborating the epidemiologic and traceback findings. CDC has established a National Network for Molecular Subtyping (5), with four area laboratories in Massachusetts, Minnesota, Texas, and Washington serving as reference PFGE laboratories; other state laboratories also have begun using the same method. Standardized laboratory procedures and electronic links to share data among laboratories and CDC make this network a key element of the recently announced President’s Food Safety Initiative (6) and an important aspect of outbreak detection and coordination.”