Sprout Food-Borne Illness Outbreaks

Until the development of ISS's trusted and proven process for screening sprouting seeds, sprout seeds were the root cause of many outbreaks of food-borne illness. At ISS, we have been involved in the sprouts industry since its inception and have led the industry in mitigating the risks of outbreaks and making sprouts a safe food to grow and eat. This page chronicles some of the challenges our industry faced in its earliest years.

Data Concerning Historic Sprout Outbreaks

According to the Center for Science in the Public Interest, in a paper called "Outbreak Alert! 2002, "Closing the Gaps in Our Federal Food-Safety Net", sprouts made up 7% of the outbreaks from fruit and vegetables during the period of 1990-2002 (September). 

Produce Outbreaks

1990-2002

Vegetables

Potatoes

3%

Mushrooms

4%

Home-canned vegetables 

5%

Sprouts

7%

Produce Dishes

9%

Other Vegetables

14%

Lettuce

11%

Salad

28%

Fruit

Melon

2%

Berries

4%

Other Fruits

13%

Total

100%

Table 1. Sprouts were suspected in 7% of the produce related outbreaks from 1990 to 2002

Sprout Related Outbreaks

Although there have been documented outbreaks in sprouts since 1973, federal regulators, public health officials, and the sprouting industry did not wake up to dangers associated with sprouting until about 1996.  All parties concerned, including ISS, were bent on coming up with a way to sanitize the seed.  Between 1998 and June 2006, there have been 36 reported outbreaks in the world that were attributed to sprouts.  Twenty-seven of which involved US and/or Canadian sprout growers. 

US Sprout Related Outbreaks 1996 - 2004

(FDA figures)

Year

Alfalfa sprouts & mixes with alfalfa sprouts

Clover sprouts

Mung bean sprouts

Total

Outbreaks

Cases

1996

1

1

 

2

650

1997

3

 

 

3

277

1998

3

 

 

3

48

1999

5

1

 

6

389

2000

 

 

1

1

75

2001

1

 

2

3

88

2002

1

 

1

2

21

2003

5

 

 

5

52

2004

2

 

 

2

36

Total

21

2

4

27

1633

Table 2.  Sprouts were suspected in 27 outbreaks and 1633 cases from 1996 to May 2005

Update:  There have been additional US sprout related outbreaks reported since 2004.

Several of the Outbreaks Appear to be Related

  • Three separate bean sprout outbreaks of Salmonella were reported to be the SAME phage type. (18, 24, 52, 89)  According to the Canada Communicable Disease Report,

"This outbreak represents the first known occurrence of SE PT 913 infection in humans." (18) 

  • Three separate alfalfa sprout outbreaks of E.coli 0157:H7 were reported to have the SAME PFGE pattern.(31, 101) According to the investigative report,

 "These Pulse patterns had never been previously identified in the United States." (31)  

  • One outbreak reportedly involved FOUR strains of salmonella in ONE seed lot.  From the report:

"Six opened packages of alfalfa sprouts were taken from cases' homes? Two packages were positive for S. paratyphi B var java, PT "Worksop", PFGE pattern A1. One package was positive for S. litchfield, one for S. thompson and one for S. newport; one package was negative." (33) 

  • A 1996  outbreak appears to have matched the seed from a 1995 outbreak.  From the report on the 1996 outbreak:

"PFGE testing on four isolates from University A students and two from University B students showed them to be identical to the 1995 outbreak strain." (117)

Sprouting Seed Often to Blame for Outbreaks

Since 1988, with one exception, seed have been the likely source of contamination in every outbreak in which the source was determined.

World Sprout Related Outbreaks 1988 - Early 2005

(Food Standards Agency, UK.)

Year

Pathogen

Cases

Location(s)

Type of sprout

Likely source of contamination

1988

S. Saint-Paul, S. Havana, S. Muenchen

148

Sweden

Mung

ND

1988

S. Saint Paul

143

United Kingdom

Mung

Seed

1988

S. Virchow

7

United Kingdom

Mung

ND

1989

S. Gold-Coast

31

United Kingdom

Cress

Seed and/or sprout grower

1990

S. Anatum

15

Washington

Alfalfa

ND

1992

S. enterica

272

Finland

Alfalfa

ND

1994

S. Bovis mordificans

492

Finland, Sweden

Alfalfa

Seed

1995

S. Stanley

242

Finland, 6 US States

Alfalfa

Seed

1995

S. Newport

154

Denmark (Probably USA and Canada)

Alfalfa

Seed

1995

S. Newport

133

7 US States, Canada, Denmark

Alfalfa

Seed

1996

E. coli O157:H7

5,727

Japan

Radish

Seed

1996

E. coli O157:H7

126

Japan

Radish

Sprout growers

1996

S. Montevideo and S. Meleagridis

492

California, Nevada

Alfalfa

Seed and/or sprout grower

1997

S. Anatum & S. Infantis

109

Kansas, Missouri

Alfalfa

Seed

1997

E. coli O157:H7

79

4 US States

Alfalfa

Seed

1997

E. coli O157:H7

108

Michigan, Virginia

Alfalfa

Seed

1997

S. Meleagridis

78

Canada

Alfalfa

Seed (organic)

1997

S. Senftenberg

60

California, Nevada

Alfalfa

Seed and/or sprout drum

1998

S. Havana

18

2 US States

Alfalfa

Seed

1998

S. Cubana

22

5 US States

Alfalfa

Seed

1998

E. coli O157:H7

8

California, Nevada

Alfalfa, Clover

Seed and/or sprout grower

1999

S. Mbandaka

75

4 US states

Alfalfa

Seed

1999

S. Muenchen

>157

Multistate, USA

Alfalfa

Seed

1999

S. Saint-Paul,

36

California, USA

Clover

ND

1999

S. paratyphi var Java

51

Canada

Alfalfa

Seed

1999

S. typhimurium

120

Colorado

Alfalfa

Seed

2000

Salmonella spp.

22

California, USA

Alfalfa

ND

2000

S. Enteritidis PT 4b

27

The Netherlands

Mung

Seed

2000

S. Enteritidis

75

4 US states

Mung

ND

2001

S. Enteritidis PT 913

84

Canada

Mung

Seed

2001

S. Kottbus

31

4 US states

Alfalfa

Seed

2002

S. Enteritidis

n/a

Maine

Mung

ND

2003

S. Saint-Paul

>9

Oregon, Washington

Alfalfa

ND

ND = Non Determined

Table 3.  Seed was suspected in all but one of the outbreak in which a likely source was determined.