Att D - MMWR

Morbidity and Mortality Weekly Report

Surveillance for Foodborne Disease Outbreaks — United States, 2008
Foodborne agents cause an estimated 48 million illnesses
annually in the United States, including 9.4 million illnesses
from known pathogens (1,2). CDC collects data on foodborne
disease outbreaks submitted from all states and territories
through the Foodborne Disease Outbreak Surveillance System.
During 2008, the most recent year for which data are finalized,
1,034 foodborne disease outbreaks were reported, which
resulted in 23,152 cases of illness, 1,276 hospitalizations,
and 22 deaths. Among the 479 outbreaks with a laboratoryconfirmed single etiologic agent reported, norovirus was the
most common, accounting for 49% of outbreaks and 46% of
illnesses. Salmonella was the second most common, accounting
for 23% of outbreaks and 31% of illnesses. Among the 218
outbreaks attributed to a food vehicle with ingredients from only
one of 17 defined food commodities (3), the top commodities
to which outbreaks were attributed were poultry (15%), beef
(14%), and finfish (14%), whereas the top commodities to
which outbreak-related illnesses were attributed were fruits
and nuts (24%), vine-stalk vegetables (23%), and beef (13%).
Outbreak surveillance provides insights into the agents that
cause foodborne illness, types of implicated foods, and settings
where transmission occurs. Public health, regulatory, and
food industry professionals can use this information to target
prevention efforts against pathogens and foods that cause the
most foodborne disease outbreaks.
Since 1992, CDC has defined a foodborne disease outbreak
as the occurrence of two or more similar illnesses resulting
from ingestion of a common food. State, local, and territorial
health department officials use a standard, Internet-based form
to voluntarily submit reports of foodborne outbreaks to CDC.
An online toolkit of clinical and laboratory information is
available to support investigation and reporting of outbreaks.*
This report includes outbreaks in which the first illness
occurred in 2008 and were reported to CDC by June 28,
2011. Data requested for each outbreak include the number
of illnesses, hospitalizations, and deaths; the etiologic agent
(confirmed or suspected†); the implicated food or foods;
and the setting of food preparation and consumption.
CDC classifies foods as one of 17 commodities if a single
contaminated ingredient is identified or if all ingredients
belong to that commodity (3). Outbreaks that could not be
assigned to one of the 17 commodities, or for which the report
* The reporting form is available at http://www.cdc.gov/outbreaknet/nors; the
toolkit is available at http://www.cdc.gov/outbreaknet/references_resources.
† Definitions are available at http://www.cdc.gov/outbreaknet/references_
resources/guide_confirming_diagnosis.html.

contained insufficient information for commodity assignment,
were not attributed to any commodity. Population-based rates
of reported outbreaks were calculated for each state, using U.S.
Census estimates of the 2008 state populations.§
Public health officials from 47 states, the District of
Columbia, and Puerto Rico reported 1,034 outbreaks;
multistate outbreaks involving three additional states (Indiana,
Mississippi, and Montana) were reported by CDC (Figure).
The number (1,034) of outbreaks was 10% lower than the
annual average reported (1,151) for 2003–2007, and the
number of outbreak-related illnesses was 5% lower (23,152
versus 24,400) (Table 1). An average of 24 (range: 2–128)
outbreaks were reported from each state or territory (Figure).
The average rate was 0.53 (range: 0.06–2.20) outbreaks per
100,000 population.
Of the total number of outbreak-related foodborne illnesses,
1,276 (6%) resulted in hospitalization. Salmonella was the most
common cause of outbreak-related hospitalizations, causing
62% of hospitalizations reported, followed by Shiga toxin–
producing Escherichia coli (STEC) (17%) and norovirus (7%).
Outbreaks caused by Clostridium botulinum resulted in the
highest proportion of persons hospitalized (90%), followed by
Listeria outbreaks (76%). Among the 22 deaths associated with
foodborne disease outbreaks in 2008, 20 were attributed to
bacterial etiologies (13 Salmonella, three Listeria monocytogenes,
three STEC [two O157, one O111], one Staphylococcus), one
to norovirus, and one to a mycotoxin.
A single confirmed or suspected etiologic agent was identified
in 666 (64%) outbreaks (479 confirmed, 187 suspected)
(Table 1). Among the 479 outbreaks with a single confirmed
etiologic agent, viruses caused 234 (49%) outbreaks, bacteria
caused 212 (44%) outbreaks, chemicals and toxins caused
27 (6%) outbreaks, and parasites caused six (1%) outbreaks.
Norovirus was the most common cause of outbreaks and
illnesses, accounting for 233 (49%) of the confirmed, singleetiology outbreaks and 7,235 (46%) illnesses. Salmonella was
the second most common etiologic agent, causing 110 (23%)
confirmed, single-etiology outbreaks and 52% of those caused
by bacteria. Among the 108 Salmonella outbreaks with a
serotype reported, Enteritidis was the most common serotype,
causing 29 (27%) confirmed, single-etiology outbreaks. STEC
caused 36 (8%) confirmed, single-etiology outbreaks, of which
35 were caused by serogroup O157.
§ Available

at http://www.census.gov/popest/datasets.html.

MMWR / September 9, 2011 / Vol. 60 / No. 35

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Morbidity and Mortality Weekly Report

FIGURE. Rate of reported foodborne disease outbreaks per 100,000 population* and number of outbreaks,† by affected states and major
etiology group§ — Foodborne Disease Outbreak Surveillance System, United States, 2008

All outbreaks (N = 1,206)¶
48

15

2

33

7
9

128

39
8

6

10
11

62
26

3

65

44
7
20

57

43

8

2

8

17

Bacterial (N = 449)¶

94

77 4
7

5

6

3

25

15
14
4
27

7 16
14

26

3

29
6 8 15

12

5
4

7

16
3

5
4

8

25

14

7

17

4 23
4
11

3

14

2

5

12

2

6
89

18

2

10

40

27

4
4

7

8

7

2

3

3

15
4 12
12

7

7
6

11
5
7
10
2
8

6

9

22

0.97–2.20

0.54–0.87

0.54–0.96

0.30–0.53

0.30–0.53

0.17–0.29

0.17–0.29

0.10–0.16

0.06–0.16

0.02–0.09

Chemical and toxin (N = 36)

Viral (N = 355)

2

18
5

1

5
1

1
1

2

1

6

43

1

3

1

2

1

1

1

18

10
1

3
26

42

13

4

1
11

10

5

15

2

3
1

4

1
1

1

1

3

6

28

12

9

13

5

2
1
8
1
1
13

2

26

0.16–0.31

0.28–0.82

0.06–0.15

0.19–0.27

0.03–0.05

0.09–0.18

0.003–0.02

0.01–0.08

No reports

No reports

* Cutpoints for outbreak rate categories determined using Jenks Natural Breaks Optimization in ArcGIS. Legend differs for each etiology.
† Number of reported outbreaks in each state.
§ Analysis restricted to outbreaks caused by a single confirmed or suspected etiology.
¶ Includes 17 multistate outbreaks that are assigned as an outbreak to each state involved.

A food vehicle was reported for 481 (47%) outbreaks,
among which the food vehicle could be assigned to one of
the 17 commodities in 218 (45%) of the outbreaks (Table 2).
The commodities most commonly implicated were poultry
(32 outbreaks), beef (31), and finfish (30). The commodities
associated with the most outbreak-related illnesses were
fruits-nuts (1,755 illnesses), vine-stalk vegetables (1,622),
and beef (952). The pathogen-commodity pairs responsible
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MMWR / September 9, 2011 / Vol. 60 / No. 35

for the most outbreaks were norovirus in leafy vegetables (18
outbreaks), ciguatoxin in finfish (14), STEC O157 in beef (12),
and Salmonella in poultry (11). The pathogen-commodity
pairs responsible for the most outbreak-related illnesses were
Salmonella in vine-stalk vegetables (1,604 illnesses) and
Salmonella in fruits-nuts (1,401).
Seventeen multistate outbreaks (i.e., outbreaks in which
the exposure occurred in more than one state) were reported.

Morbidity and Mortality Weekly Report

TABLE 1. Number and percentage of reported foodborne outbreaks and outbreak-associated illnesses, by etiology* — Foodborne Disease
Outbreak Surveillance System, United States, 2008, and 2003–2007 mean annual totals
Outbreaks
2008

Hospitalizations

2008

2003–2007

Mean annual
total†

Total
Etiology

Illnesses
2003–2007

2008

2003–2007

Mean annual
total†

Total

Mean annual
total†

Total

CE

SE

No

(%)

No.

(%)

CE

SE

No.

(%)

No.

(%)

CE

110
21
36

7
19
—

117
40
36

(18)
(6)
(5)

129
44
27

(17)
(6)
(4)

4,883
965
920

77
444
—

4,960
1,409
920

(27)
(8)
(5)

3,290
1,815
402

(17)
(9)
(2)

791
3
214

21
3
6

4
12
8

25
15
14

(4)
(2)
(2)

22
18
35

(3)
(2)
(5)

604
73
257

11
49
54

615
122
311

(3)
(1)
(2)

623
138
472

(3)
(1)
(2)

SE

No.

(%)

No.

(%)

6
1
—

797
4
214

(66)
(<1)
(18)

369
12
115

(49)
(2)
(15)

20
—
12

5
1
—

25
1
12

(2)
(<1)
(1)

13
—
20

(2)
(0)
(3)

Bacterial
Salmonella§
Clostridium perfringens
Escherichia coli, Shiga
toxin–producing (STEC)¶
Campylobacter**
Bacillus cereus
Staphylococcus
enterotoxin††
Shigella§§
Clostridium botulinum
Other bacterial
Listeria¶¶
Vibrio parahaemolyticus
Vibrio other
Escherichia coli,
enterotoxigenic
Brucella sp.
Yersinia enterocolitica
Total

6
4
1
3
1
—
—

—
—
2
—
—
1
—

6
4
3
3
1
1
—

(1)
(1)
(<1)
(<1)
(<1)
(<1)
(0)

11
3
15
2
5
1
2

(1)
(<1)
(2)
(<1)
(1)
(<1)
(<1)

170
10
64
33
2
—
—

—
—
24
—
—
3
—

170
10
88
33
2
3
—

(1)
(<1)
(<1)
(<1)
(<1)
(<1)
(0)

500
10
117
13
109
2
125

(3)
(<1)
(1)
(<1)
(1)
(<1)
(1)

4
9
—
25
—
—
—

—
—
—
—
—
—
—

4
9
—
25
—
—
—

(<1)
(1)
(0)
(2)
(0)
(0)
(0)

12
8
1
11
1
—
1

(2)
(1)
(<1)
(1)
(<1)
(0)
(<1)

—
—
212

—
—
53

—
—
265

(0)
(0)
(40)

1
1
316

(<1)
(<1)
(41)

—
—
7,981

—
—
662

—
—
8,643

(0)
(0)
(47)

2
3
7,623

(<1)
(<1)
(40)

—
—
1,078

—
—
13

—
—
1,091

(0)
(0)
(91)

1
1
566

(<1)
(<1)
(75)

Chemical and toxin
Scombroid toxin/histamine
Ciguatoxin
Cleaning agents
Heavy metals
Other chemical
Mycotoxins
Paralytic shellfish poison
Plant/herbal toxins
Neurotoxic shellfish poison
Puffer fish tetrodotoxin
Other natural toxins
Total

10
11
—
2
1
1
1
1
—
—
—
27

2
3
3
—
1
—
—
—
—
—
—
9

12
14
3
2
2
1
1
1
—
—
—
36

(2)
(2)
(<1)
(<1)
(<1)
(<1)
(<1)
(<1)
(0)
(0)
(0)
(5)

31
12
—
1
12
2
1
—
1
—
1
63

(4)
(2)
(0)
(<1)
(2)
(<1)
(<1)
(0)
(<1)
(0)
(<1)
(8)

51
60
—
54
39
3
3
6
—
—
—
216

4
21
14
—
3
—
—
—
—
—
—
42

55
81
14
54
42
3
3
6
—
—
—
258

(<1)
(<1)
(<1)
(<1)
(<1)
(<1)
(<1)
(<1)
(0)
(0)
(0)
(1)

125
51
1
4
147
18
2
3
4
1
4
361

(1)
(<1)
(<1)
(<1)
(1)
(<1)
(<1)
(<1)
(<1)
(<1)
(<1)
(2)

1
—
—
—
—
3
3
6
—
—
—
13

—
—
—
—
2
—
—
—
—
—
—
2

1
—
—
—
2
3
3
6
—
—
—
15

(<1)
(0)
(0)
(0)
(<1)
(<1)
(<1)
(<1)
(0)
(0)
(0)
(1)

4
8
—
—
7
8
2
—
2
1
1
33

(1)
(1)
(0)
(0)
(1)
(1)
(<1)
(0)
(<1)
(<1)
(<1)
(4)

Parasitic
Cyclospora
Cryptosporidium
Giardia
Trichinella
Other parasitic
Total

3
2
1
—
—
6

—
—
—
—
—
—

3
2
1
—
—
6

(<1)
(<1)
(<1)
(0)
(0)
(1)

2
2
2
1
—
7

(<1)
(<1)
(<1)
(<1)
(0)
(1)

66
32
8
—
—
106

—
—
—
—
—
—

66
32
8
—
—
106

(<1)
(<1)
(<1)
(0)
(0)
(1)

185
39
44
1
4
273

(1)
(<1)
(<1)
(<1)
(<1)
(1)

2
—
—
—
—
2

—
—
—
—
—
—

2
—
—
—
—
2

(<1)
(0)
(0)
(0)
(0)
(<1)

—
1
—
—
—
3

(0)
(<1)
(0)
(0)
(0)
(<1)

Viral
Norovirus
Hepatitis A
Rotavirus
Other viral
Total

233
1
—
—
234

123
—
1
1
125

356
1
1
1
359

(54)
(<1)
(<1)
(<1)
(54)

376
5
1
3
385

(49)
(1)
(<1)
(<1)
(50)

7,235
22
—
—
7,257

1,940
—
27
9
1,976

9,175
22
27
9
9,233

(50) 10,534
(<1)
234
(<1)
17
(<1)
126
(51) 10,911

(55)
(1)
(<1)
(1)
(57)

70
4
—
—
74

20
—
—
—
20

90
4
—
—
94

(7)
(<1)
(0)
(0)
(8)

117
37
—
3
158

(15)
(5)
(0)
(<1)
(21)

Known etiology***
Unknown etiology†††
Multiple etiologies
Total

479
—
11
490

187
—
7
194

666
350
18
1,034

(64)
(34)
(2)
(100)

771
344
36
1,151

(67)
(30)
(3)
(100)

15,560
—
540
16,100

2,680 18,240
—
4,262
110
650
2,790 23,152

(79) 19,167
(18)
4,379
(3)
854
(100) 24,400

(79)
(18)
(3)
(100)

1,167
—
33
1,200

35
—
1
36

1,202
40
34
1,276

(94)
(3)
(3)
(100)

759
50
52
861

(88)
(6)
(6)
(100)

Abbreviations: CE = confirmed etiology, SE = suspected etiology.
* If at least one etiology was laboratory-confirmed, the outbreak was considered to have a confirmed etiology. If no etiology was laboratory-confirmed, but an etiology was reported based
on clinical or epidemiologic features, the outbreak was considered to have a suspected etiology.
† Because of rounding, numbers might not add up to the etiology category total or the known etiology total.
§ Salmonella serotypes accounting for more than five reported outbreaks include: Enteriditis (30 outbreaks), Typhimurium (18), Heidelberg (eight), and Braenderup (six).
¶
STEC O111 (one confirmed outbreak), STEC O157:H7 (32 confirmed outbreaks), and STEC O157:NM(H-) (three confirmed outbreaks).
** Campylobacter coli (one confirmed outbreak, no suspected outbreaks), Campylobacter jejuni (15 confirmed outbreaks, four suspected outbreaks).
†† Staphylococcus aureus (six confirmed outbreaks, five suspected outbreaks) and Staphylococcus unknown (three suspected outbreaks).
§§ Shigella sonnei (six confirmed outbreaks, no suspected outbreaks).
¶¶ Listeria monocytogenes (three confirmed outbreaks, no suspected outbreaks).
*** The denominator for the etiology percentages is the known etiology total. The denominator for the known etiology, unknown etiology, and multiple etiologies percentages is the total.
††† An etiologic agent was not confirmed or suspected based on clinical, laboratory, or epidemiologic information.

MMWR / September 9, 2011 / Vol. 60 / No. 35

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Morbidity and Mortality Weekly Report

TABLE 2. Number of reported foodborne disease outbreaks and outbreak-associated illnesses, by etiology* and food commodity — Foodborne
Disease Outbreak Surveillance System, United States, 2008
Outbreaks (illnesses)
Attributed to a single
commodity

Etiology
Bacterial
Salmonella†
Clostridium perfringens
Escherichia coli, Shiga toxin–producing (STEC)§
Campylobacter¶
Bacillus cereus
Staphylococcus enterotoxin**
Shigella††
Clostridium botulinum
Other bacterial
Listeria§§
Vibrio parahaemolyticus
Vibrio other
Total
Chemical and toxin
Scombroid toxin/histamine
Ciguatoxin
Cleaning agents
Heavy metals
Other chemical
Mycotoxins
Paralytic shellfish poison
Plant/herbal toxins
Total
Parasitic
Cyclospora
Cryptosporidium
Giardia
Total
Viral
Norovirus
Hepatitis A
Rotavirus
Other viral
Total
Known etiology¶¶
Unknown etiology***
Multiple etiologies
Total

Attributed to food vehicle
containing >1 commodity

Attributed to
unknown commodity

Total

40
20
21
17
7
3
0
1
1
2
1
0
113

(3,690)
(897)
(427)
(538)
(70)
(27)
(0)
(2)
(64)
(28)
(2)
(0)
(5,745)

24
12
5
2
7
8
0
2
2
1
0
0
63

(734)
(226)
(98)
(6)
(50)
(124)
(0)
(6)
(24)
(5)
(0)
(0)
(1,273)

53
8
10
6
1
3
6
1
0
0
0
1
89

(536)
(286)
(395)
(71)
(2)
(160)
(170)
(2)
(0)
(0)
(0)
(3)
(1,625)

117
40
36
25
15
14
6
4
3
3
1
1
265

(4,960)
(1,409)
(920)
(615)
(122)
(311)
(170)
(10)
(88)
(33)
(2)
(3)
(8,643)

11
14
0
0
0
1
1
1
28

(53)
(81)
(0)
(0)
(0)
(3)
(3)
(6)
(146)

1
0
1
1
0
0
0
0
3

(2)
(0)
(3)
(2)
(0)
(0)
(0)
(0)
(7)

0
0
2
1
2
0
0
0
5

(0)
(0)
(11)
(52)
(42)
(0)
(0)
(0)
(105)

12
14
3
2
2
1
1
1
36

(55)
(81)
(14)
(54)
(42)
(3)
(3)
(6)
(258)

3
0
0
3

(66)
(0)
(0)
(66)

0
0
0
0

(0)
(0)
(0)
(0)

0
2
1
3

(0)
(32)
(8)
(40)

3
2
1
6

(66)
(32)
(8)
(106)

35
1
0
0
36
180
33
5 
218

(618)
(22)
(0)
(0)
(640)
(6,575)
(409)
(193)
(7,177)

94
0
1
0
95
161
67
9
237

(2,484)
(0)
(27)
(0)
(2,511)
(3,791)
(577)
(202)
(4,570)

227
0
0
1
228
325
250
4
579

(6,073)
(0)
(0)
(9)
(6,082)
(7,852)
(3,276)
(255)
(11,383)

356
1
1
1
359
666
350
18
1,034

(9,175)
(22)
(27)
(9)
(9,233)
(18,240)
(4,262)
(650)
(23,152)

* If at least one etiology was laboratory-confirmed, the outbreak was considered to have a confirmed etiology. If no etiology was laboratory-confirmed, but an
etiology was reported based on clinical or epidemiologic features, the outbreak was considered to have a suspected etiology.
† Salmonella serotypes accounting for more than five reported outbreaks included: Enteriditis (30 outbreaks), Typhimurium (18), Heidelberg (eight), and Braenderup (six).
§ STEC O111 (one confirmed outbreak), STEC O157:H7 (32 confirmed outbreaks), and STEC O157:NM(H-) (three confirmed outbreaks).
¶ Campylobacter coli (one confirmed outbreak, no suspected outbreaks), Campylobacter jejuni (15 confirmed outbreaks, four suspected outbreaks).
** Staphylococcus aureus (six confirmed outbreaks, five suspected outbreaks) and Staphylococcus unknown (three suspected outbreaks).
†† Shigella sonnei (six confirmed outbreaks, no suspected outbreaks).
§§ Listeria monocytogenes (three confirmed outbreaks, no suspected outbreaks).
¶¶ The denominator for the etiology percentages is the known etiology total. The denominator for the known etiology, unknown etiology, and multiple etiologies
percentages is the total.
*** An etiologic agent was not confirmed or suspected based on clinical, laboratory or epidemiologic information.

Multistate outbreaks involved a median of seven (range: 2–46)
states. Nine were caused by Salmonella. The etiologic agent was
isolated from an implicated food in six of these outbreaks. The
foods in these six outbreaks were cantaloupe, cereal, ground
turkey, ground white pepper, jalapeño and serrano peppers
(4), and peanut butter and peanut paste (5). Six multistate
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MMWR / September 9, 2011 / Vol. 60 / No. 35

outbreaks were caused by STEC O157; STEC was isolated
from ground beef in two outbreaks. Two multistate outbreaks
were caused by Listeria. One outbreak was caused by Listeria
in Mexican-style cheese made from pasteurized milk, the other
by Listeria in sprouts.

Morbidity and Mortality Weekly Report

Among the 868 outbreaks with a known single setting where
food was consumed, 52% resulted from food consumed in a
restaurant or deli, 15% in a private home, and the remainder
in other locations.¶ Among the 481 outbreaks for which
a food vehicle was identified, 19 (4%) resulted in product
recalls.** The recalled foods were beef (five outbreaks), dietary
supplements (two), cantaloupe (two), alfalfa sprouts (two),
and cereal, cheese, fish, jalapeño and serrano peppers, melon,
pancakes, spices, and peanut butter and peanut paste (one
each). One beef establishment had two product recalls (6).
Reported by

L. Hannah Gould, PhD, Amie L. Nisler, MPH, Karen M.
Herman, MSPH, Dana J. Cole, DVM, PhD, Ian T. Williams,
PhD, Barbara E. Mahon, MD, Patricia M. Griffin, MD, Div
of Foodborne, Waterborne, and Environmental Diseases, National
Center for Emerging and Zoonotic Infectious Diseases; Aron J.
Hall, DVM, Div of Viral Diseases, National Center for
Immunization and Respiratory Diseases, CDC. Corresponding
contributor: L. Hannah Gould, [email protected], 404-639-3315.

What is already known about this topic?
Surveillance for foodborne disease outbreaks can identify
opportunities to prevent and control foodborne diseases, which
cause millions of illnesses in the United States each year.
What is added by this report?
Among the 1,034 foodborne disease outbreaks reported in
2008, most of the single, laboratory-confirmed agents of
outbreak-associated illnesses were norovirus and Salmonella.
The largest numbers of foodborne disease outbreaks were
associated with beef, poultry, and fish, and the largest numbers
of outbreak-associated illnesses were associated with vine-stalk
vegetables, fruits-nuts, and beef.
What are the implications for public health practice?
Public health, regulatory, and food industry professionals can
use surveillance data to target prevention efforts against
pathogens and foods that cause the most foodborne disease
outbreaks.

As for the previous 10 years, beef, poultry, and finfish
were the commodities associated with the largest number of
foodborne outbreaks. As a result of several large multistate
outbreaks, vine-stalk vegetables, fruits-nuts, and beef were the
commodities with the most outbreak-associated illnesses. The
number of STEC O157 and Salmonella Enteritidis outbreaks
in 2008 continued to exceed the Healthy People 2010 food
safety objective to reduce outbreaks of infections caused by
key foodborne bacteria (objective 10-2) (7). The 35 outbreaks
caused by STEC O157 was more than triple the Healthy
People 2010 target of 11, and the 29 outbreaks attributed to
Salmonella serotype Enteritidis exceeded the target of 22 by
nearly a third.
Salmonella was the leading cause of hospitalizations and
deaths and the cause of more than half of the multistate
outbreaks. Two of the most common foods implicated in
outbreaks of Salmonella infections have been poultry and
eggs or egg products; consequently, several U.S. food safety
initiatives have been implemented since the 1960s to limit
contamination of these commodities. Recent Food and Drug
Administration safety initiatives include additional regulations
to improve the safety of shell eggs that went into effect in 2010.
In addition, new U.S. Department of Agriculture Food Safety

and Inspection Service performance standards lowered the
allowable limit for Salmonella contamination of young chicken
and turkey carcasses at processing plants, effective July 2011.††
Norovirus remained the leading cause of outbreaks and
illnesses in 2008. Most norovirus outbreaks with an implicated
food vehicle were attributed to foods containing more than
one commodity; a specific food vehicle was reported in a
lower proportion of norovirus outbreaks than in outbreaks
attributed to other causes. In norovirus outbreaks caused by
a single food commodity, produce commodities that typically
are not cooked, (i.e., leafy vegetables), continued to be the
leading commodities implicated. Many outbreaks result from
contamination of food during preparation and service via
unwashed or improperly washed hands of food workers who
are shedding norovirus in their stools. This often results in
contamination of more than one food item. Contaminated
environmental surfaces and infected consumers also lead to
transmission of norovirus in food service settings. Additionally,
norovirus contamination can occur during food production
and processing, resulting in widespread exposure.
The findings in this report are subject to at least four
limitations. First, only a small proportion of foodborne illnesses
reported each year are identified as associated with outbreaks.
The extent to which the distributions of food vehicles and
preparation and consumption settings implicated in foodborne
disease outbreaks reflect the same sources of infection and
settings of sporadic illnesses is difficult to determine (8).

¶ Additional

†† Egg safety final rule, available at http://www.fda.gov/food/foodsafety/product-

Editorial Note

data on foodborne disease outbreaks and illnesses for the 17
commodity categories and by settings where food was consumed is available
at http://www.cdc.gov/outbreaknet/surveillance_data.html.
** Additional information on product recalls is available at http://www.fda.gov/
safety/recalls/default.htm and http://www.fsis.usda.gov/fsis_recalls/index.asp.

specificinformation/eggsafety/eggsafetyactionplan/ucm170615.htm; and Food
Safety and Inspection Service new performance standards for Salmonella and
Campylobacter in young chicken and turkey slaughter establishments; new
compliance guides, available at http://www.fsis.usda.gov/oppde/rdad/
frpubs/2010-0029.pdf.

MMWR / September 9, 2011 / Vol. 60 / No. 35

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Morbidity and Mortality Weekly Report

Second, CDC’s outbreak surveillance database is dynamic;
agencies can submit new reports and can change or delete
previous reports as new information becomes available.
Therefore, the results of this analysis might differ from those
published earlier or subsequently. Third, many reported
outbreaks had an unknown etiology, an unknown food
vehicle, or both, and conclusions drawn from outbreaks with
a confirmed or suspected etiology or food vehicle might not
apply to outbreaks of unknown etiology or food source. Finally,
because of variations in outbreak detection, investigation, and
reporting, comparisons with previous years should be made
with caution.
Ensuring adequate epidemiologic and regulatory investigative
capacity at the state and federal levels is essential to identify
outbreak sources and implement timely control measures (9).
Public health, regulatory, and food industry professionals use
foodborne outbreak surveillance data to target prevention efforts
against pathogens and foods that cause the most foodborne
disease outbreaks. Additional information on outbreaks,
including the Foodborne Outbreak Online Database (FOOD),
is available at http://www.cdc.gov/foodborneoutbreaks.

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MMWR / September 9, 2011 / Vol. 60 / No. 35

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