Foodborne Disease Outbreaks, 2019

Background

Known pathogens are estimated to cause 9.4 million foodborne illnesses each year in the United States.1 Although relatively few of these illnesses occur in the setting of a recognized outbreak, data collected during outbreak investigations provide insight into the pathogens and foods that cause illness. Public health officials, regulatory agencies, and the food industry can use these data to inform efforts to prevent foodborne illness.

Findings

Outbreaks were reported by public health officials from 44 states, Washington, D.C., and Puerto Rico (Figure). The median reporting rate per million population was 4.51 outbreaks; rates ranged from 0.34 in Mississippi to 11.22 in Vermont.

Etiologic agents

A single etiologic agent was confirmed in 417 (48%) outbreaks, resulting in 7,551 (64%) illnesses (Table 1).

Salmonella was the most common cause of confirmed, single-etiology outbreaks, accounting for 115 (28%) outbreaks and 2,278 (30%) illnesses. Among the 111 Salmonella outbreaks with a serotype reported, the most common serotypes were

1. Enteritidis (31 outbreaks, 28%)
2. Typhimurium (9, 8%)
3. Javiana (8, 7%)
4. Newport (8, 7%)
5. Infantis (6, 5%)

Norovirus was the next most common cause of confirmed, single-etiology outbreaks, accounting for 106 (25%) outbreaks and 2,360 (31%) illnesses. Cyclospora caused 42 (10%) confirmed, single-etiology outbreaks and Shiga toxin-producing E. coli (STEC) caused 37 (9%) confirmed, single-etiology outbreaks, of which 27 (73%) were caused by O157. Among all outbreaks, 171 (19%) reports did not include an etiologic agent.

The most outbreak-associated hospitalizations were caused by

1. Salmonella (573 hospitalizations, 62%)
2. STEC (217, 24%)
3. Hepatitis A virus (25, 3%)

Outbreaks caused by Clostridium botulinum (11 hospitalizations, 100%) and Listeria monocytogenes (7 hospitalizations, 100%) resulted in the highest percentage of ill persons hospitalized, followed by hepatitis A virus (25, 60%), and STEC (212, 35%).

Among the 7 deaths reported, all were attributed to bacterial etiologies (Salmonella [3], C. botulinum [2], STEC [1], and Listeria [1]).

Food categories implicated

A confirmed or suspected food source was reported for 336 (38%) outbreaks. In 221 (66%) of these outbreaks, the food could be classified into a single category (Table 2a).

The categories most implicated were

1. Fish (53 outbreaks, 24%)
2. Chicken (26 outbreaks, 12%)
3. Herbs (22 outbreaks, 10%)
4. Mollusks (19 outbreaks, 9%)

The most outbreak-associated illnesses were from

1. Herbs (770 illnesses, 19%)
2. Fruits (585, 14%)
3. Chicken (501, 12%)
4. Vegetable row crops (400, 10%)
5. Beef (312, 8%)

Etiologic agents and food category pairs

The pathogen-food category pairs responsible for most outbreaks with a single confirmed etiologic agent were ciguatoxin in fish (31 outbreaks), Cyclospora in herbs (18), scombroid toxin/histamine in fish (18), Salmonella in chicken (12), and Vibrio parahaemolyticus in mollusks (9) (Table 2b).

The pathogen-food category pairs responsible for the most illnesses in outbreaks with a single confirmed etiologic agent were Cyclospora in herbs (716 illnesses), Salmonella in fruits (508), Salmonella in chicken (415), STEC in vegetable row crops (287), and STEC in beef (121).

The pathogen-food category pairs responsible for the most hospitalizations in outbreaks with a single confirmed etiologic agent were Salmonella in fruits (172 hospitalizations), STEC in vegetable row crops (129), Salmonella in chicken (76), Salmonella in beef (26), and STEC in beef (24).

Deaths were reported for the following pathogen-food category pairs: Salmonella in chicken (1 death), Salmonella in beef (1), C. botulinum in other aquatic animals (1), and C. botulinum in root and other underground vegetables (1).

Among all outbreaks reported in 2019, 141 (16%) outbreaks did not report an etiologic agent or a food source.

Location of food preparation

Among the 766 outbreaks and 9,535 illnesses with a reported single location where food was prepared, 512 outbreaks (67%) and 4,883 associated illnesses (51%) were attributed to foods prepared in a restaurant (Table 3).

Among these, sit-down dining restaurants were the type of restaurant most reported (371 outbreaks, 48%).

Multistate outbreaks with first identified illness onset during 2019

These outbreaks involved a median of eight states (range 2–35).

Thirty-two multistate outbreaks were caused by Salmonella; the most frequent serotypes were Enteritidis (6), Javiana (4), and Braenderup (3). Fourteen multistate outbreaks were caused by STEC, 11 of which were due to serogroup O157. The remaining multistate outbreaks were caused by Vibrio parahaemolyticus (2 outbreaks), Listeria (1), Cyclospora cayetanensis (1), scombroid toxin/histamine (1), and Hepatitis A virus (1).

The confirmed food sources for multistate Salmonella outbreaks were chicken (3 outbreaks), tuna, papaya, melon, tahini, ground beef, hummus, raw tomatoes, and mixed cut fruit (1 outbreak each). In addition, chicken (4 outbreaks), prepackaged salad mix, iceberg lettuce, vegetable trays, pork, ground beef, oysters, and strawberries (1 outbreak each) were suspected sources. A food source was not identified for 10 multistate outbreaks caused by Salmonella.

The confirmed food sources for multistate STEC outbreaks were romaine lettuce (3 outbreaks), iceberg lettuce, beef, bison, frozen pizza, and pre-packaged salad (1 outbreak each). Ground beef, spinach, leafy greens, and pre-packaged salad mix (1 outbreak each) were suspected sources. Two multistate STEC outbreaks did not have a food source identified.

Raw oysters were the confirmed source in both multistate Vibrio parahaemolyticus outbreaks. No food source was identified in the multistate Listeria outbreak.

Fresh basil was the suspected source of the multistate Cyclospora cayetanensis outbreak, yellowfin tuna was the confirmed source in the multistate scombroid toxin/histamine outbreak, and blackberries were the suspected source in the multistate Hepatitis A outbreak.

Multistate outbreaks spanning multiple years

Twenty-two multistate outbreaks investigated during 2019 in which the last outbreak-associated illness occurred in 2019 were not included in the 2019 tally because the first outbreak-associated illness occurred before 2019.

Eleven multistate outbreaks were caused by Salmonella; the confirmed food sources were onions, chicken, tahini, turkey, ground turkey, raw tuna, eggs, beef, ground beef, and queso fresco type cheese (first illness onset in 2017 or 2018).

Seven multistate outbreaks were caused by Listeria; the confirmed food sources were enoki mushrooms, avocado, artisanal soft cheese, queso fresco type cheese, leafy greens, hard-boiled eggs, and deli products (first illness onset ranging from 2016 to 2018).

Three multistate outbreaks were caused by STEC, with confirmed food sources of chicken salad, ground beef, and flour (first illness onset in 2018).

One outbreak caused by raw oysters had multiple etiologies identified.

Multistate outbreaks spanning multiple years may be identified more frequently in recent years due to the increased use of whole genome sequencing technology, especially for Salmonella and Listeria, which enhances the ability to link cases with a long duration between onset of illness.

Recalls

Twenty-one outbreaks resulted in product recalls.

The foods recalled after being implicated in outbreaks for which the exposure occurred in a single state were basil (4 outbreaks), yellowfin tuna (2), tuna (2), milk (1), ground beef (1), clover sprouts (1), and oysters (1). Tuna (2 outbreaks), ground bison, ground beef, salad products, fruit luau mix, melons, basil, and tahini (1 outbreak each) were recalled in multistate outbreaks.

The data

Figure

_{*Cut points for outbreak rate categories determined using quartiles. Legend differs for each map.}

_{† Reported outbreaks in each state. Puerto Rico reported 25 outbreaks and Washington, D.C. reported 3 outbreaks (not shown).}

_{‡ Includes 52 multistate outbreaks (i.e., outbreaks in which exposure occurred in more than one state) assigned as an outbreak to each state involved. Multistate outbreaks involved a median of 8 states (range: 2–35).}

_{§ Etiologies are reported to FDOSS by the reporting site as confirmed or suspected. 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.}

Table 1

_{Abbreviations: CE = confirmed etiology, SE = suspected etiology.}

_{^*Etiology reported to FDOSS by the reporting site as confirmed or suspected. 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 causing more than five outbreaks were Enteritidis (35 outbreaks), Typhimurium (10), unknown serotype (9), Javiana (8), Newport (8), and Infantis (6). Serotypes reported here include both confirmed and suspected etiologies.}

_{^‡STEC serogroups O157 (27 outbreaks), unknown serogroup (6), O103 (3), O26 (2), O145 (1), O111 (1), multiple serogroups (1), other serogroup (1). Serogroups reported here include both confirmed and suspected etiologies.}

_{^§Campylobacter jejuni (18 outbreaks), Campylobacter unknown species (13), and Campylobacter coli (1).}

_{^¶Shigella sonnei (3 outbreaks), Shigella unknown species (2), Shigella flexneri (1).}

_{^**The denominator for the etiology percentages is the single etiology total. The denominator for the single etiology, multiple etiologies, and unknown etiology is the total. Because of rounding, numbers might not add up to the single etiology total or the total.}

_{^††If at least two etiologies are confirmed in an outbreak, it is considered a confirmed multiple etiology outbreak; otherwise it is considered a suspected multiple etiology outbreak.}

_{^‡‡ An etiologic agent was not confirmed or suspected based on clinical, laboratory, or epidemiologic information.}

Table 2a

_{^*Interagency Food Safety Analytics Collaboration (IFSAC) food categorization scheme}

_{^†Bivalve mollusks (19 outbreaks).}

_{^‡Unpasteurized dairy products (6 outbreaks) and pasteurized dairy products (1).}

_{^§Leafy vegetables (12 outbreaks) and stem vegetables (2).}

_{^¶Grains (8 outbreaks) and beans (4 outbreaks).}

_{^**Melons (3 outbreaks), sub-tropical fruits (2), small fruits (2), tropical fruits (1), and fruits not further classified (2).}

_{^††Tubers (2 outbreaks), and root/underground vegetables not further classified (1).}

_{^‡‡Solanaceous seeded vegetables (2 outbreaks).}

_{^§§Seeds (1 outbreak).}

_{^¶¶The denominator for the food category percentages is the "food reported, attributed to a single food category" total. The denominator for the "food reported attributed to a single food category", "food reported, not attributed to a single food category", and "No food reported" is the total. Because of rounding, numbers might not add up to the "food reported, attributed to a single food category" total or the total.}

Table 2b

Most common confirmed pathogen-food category pairs resulting in outbreaks, outbreak-associated illnesses, hospitalizations, and deaths — Foodborne Disease Outbreak Surveillance System, United States, 2019

_{^*Interagency Food Safety Analytics Collaboration (IFSAC) food categorization scheme. Pathogen-food category pairs are limited to outbreaks with an identified food vehicle and a single, confirmed etiology.}

Table 3

_{^*The denominator for the location percentages is the single location total. The denominator for the single location, multiple locations, and unknown location is the total. Because of rounding, numbers might not add up to the single location total or the total.}

Table 4

_{^*Implicated foods in multistate outbreaks are further classified as confirmed or suspected based on epidemiologic, traceback, and laboratory evidence. A food is considered the confirmed source if two types of evidence are obtained, while a food is considered suspected if only one type of evidence is available.}

About the data

Suggested citation

Centers for Disease Control and Prevention (CDC). Surveillance for Foodborne Disease Outbreaks, United States, 2019, Annual Report. Atlanta, Georgia: U.S. Department of Health and Human Services, CDC, 2026.