Category Archives: Cyclospora

USA – Domestically Acquired Cases of Cyclosporiasis — United States, May–June 2022

CDC

LAST UPDATED JUNE 30, 2022 4:00 PM EDT

Cyclosporiasis illnesses are reported year-round in the United States. However, during the spring and summer months there is often an increase in cyclosporiasis acquired in the United States (i.e., “domestically acquired”). The exact timing and duration of these seasonal increases in domestically acquired cyclosporiasis can vary, but reports tend to increase starting in May. In previous years the reported number of cases peaked between June and July, although activity can last as late as September. The overall health impact (e.g., number of infections or hospitalizations) and the number of identified clusters of cases (i.e., cases that can be linked to a common exposure) also vary from season to season. Previous U.S. outbreaks of cyclosporiasis have been linked to various types of fresh produce, including basil, cilantro, mesclun lettuce, raspberries, and snow peas.

At a Glance
  • Illnesses: 61
  • Hospitalizations: 6
  • Deaths: 0
  • States reporting cases: 13

CDC, along with state and federal health and regulatory officials, monitor cases of cyclosporiasis in the United States in the spring and summer months to detect outbreaks linked to a common food source. However, many cases of cyclosporiasis cannot be directly linked to an outbreak, in part because of the lack of validated laboratory “fingerprinting” methods needed to link cases of Cyclospora infection. Officials use questionnaires to interview sick people to determine what they ate in the 14-day period before illness onset. If a commonality is found, CDC and partners work quickly to determine if a contaminated food product is still available in stores or in peoples’ homes and issue advisories.

Latest Information

  • This is the first monthly report on the number of domestically acquired cyclosporiasis illnesses with onset on or after May 1, 2022. Cases continue to be reported.
  • As of June 28, 2022, 61 laboratory-confirmed cases of cyclosporiasis in people who had no history of international travel during the 14-day period before illness onset have been reported to CDC by 13 states since May 1, 2022.
    • The median illness onset date is May 31, 2022 (range: May 3–June 20, 2022).
    • At least 6 people have been hospitalized; no deaths have been reported.

USA – Will There Be a Cyclospora Outbreak in the U.S. This Summer?

Food Poisoning Bulletin

Will there be a cyclospora outbreak in the United States this summer? There have been multiple cyclospora outbreaks in the past nine years, including in 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, and 2021. This year may be no exception.

In the past, Cyclospora outbreaks have been linked to fresh produce, including cilantro, raspberries, basil, mesclun, vegetable trays, bagged salad mixes, and snow peas. The cyclospora parasite is transmitted through human feces. The oocyst must mature, or sporulate, outside of the body before it becomes infectious. This infection is not passed person-to-person.

It is very difficult to protect yourself against this parasite, since it can cling to produce, especially produce such as leafy greens and herbs, and is not easily washed or rinsed off. And since most of the foods it contaminates are eaten without being heated, there is no kill step to destroy the parasite.

USA – CDC – Lettuce, Other Leafy Greens, and Food Safety

CDC

Leafy greens arranged on a white background

Vegetables are an important part of a healthy diet. Leafy vegetables (called leafy greens on this page), such as lettuce, spinach, cabbage, kale, and bok choy, provide nutrients that help protect you from heart diseasestroke, and some cancers.

But leafy greens, like other vegetables and fruits, are sometimes contaminated with harmful germs. Washing leafy greens does not remove all germs. That’s because germs can stick to the surface of leaves and even get inside them. If you eat contaminated leafy greens without cooking them first, such as in a salad or on a sandwich, you might get sick.

Although anyone can get a foodborne illness, sometimes called food poisoning, some groups of people are more likely to get one and to have a serious illness. These groups include:

  • Adults aged 65 and older
  • Children younger than 5 years
  • People who have health problems or take medicines that lower the body’s ability to fight germs and sickness (a weakened immune system)external icon
  • Pregnant people

Eating Leafy Greens

Are leafy greens safe to eat?

Millions of servings of leafy greens are eaten safely every day in the United States. But leafy greens are occasionally contaminated enough to make people sick. To reduce your chance of getting sick, always follow the steps for safely handling and preparing leafy greens before eating or serving them.

Are leafy greens safe for my pet to eat?

Some animals can get sick from some germs that also make people sick. Always follow the steps for safely handling and preparing leafy greens before feeding them to pets and other animals. Never feed recalled food to pets or other animals.

Safely Handling and Preparing Leafy Greens

Do I need to wash all leafy greens?

Prewashed greens don’t need to be washed again. If the label on a leafy greens package says any of the following, you don’t need to wash the greens:

  • Ready-to-eat
  • Triple washed
  • No washing necessary

Prewashed greens sometimes cause illness. But the commercial washing process removes most of the contamination that can be removed by washing.

All other leafy greens should be thoroughly washed before eating, cutting, or cooking.

What is the best way to wash leafy greens?

The best way to wash leafy greens is by rinsing them under running water. Studies show that this step removes some of the germs and dirt on leafy greens and other vegetables and fruits. But no washing method can remove all germs.

Follow these steps to wash leafy greens that you plan to eat raw:

  • Wash your hands for 20 seconds with soap and water before and after preparing leafy greens.
  • Get rid of any torn or bruised leaves. Also, get rid of the outer leaves of cabbages and lettuce heads.
  • Rinse the remaining leaves under running water. Use your hands to gently rub them to help get rid of germs and dirt.
  • Dry leafy greens with a clean cloth or paper towel.

Should I soak leafy greens before washing them?

No. Do not soak leafy greens. If you soak them in a sink, germs in the sink can contaminate the greens. If you soak them in a bowl, germs on one leaf can spread to the other leaves. Rinsing leafy greens under running water is the best way to wash them.

Should I wash leafy greens with vinegar, lemon juice, soap, detergent, or produce wash?

Use plain running water to wash leafy greens and other produce. Kitchen vinegar and lemon juice may be used, but CDC is not aware of studies that show vinegar or lemon juice are any better than plain running water.

Do not wash leafy greens or other produce with soap, detergent, or produce wash. Do not use a bleach solution or other disinfectant to wash produce.

What other food safety steps should I keep in mind when I select, store, and prepare leafy greens and other produce?

  • Select leafy greens and other vegetables and fruits that aren’t bruised or damaged.
  • Make sure pre-cut produce, such as bagged salad or cut fruits and vegetables, is refrigerated or on ice at the store.
  • Separate produce from raw meat, poultry, seafood, and eggs in your shopping cart, grocery bags, and refrigerator.
  • Store leafy greens, salads, and all pre-cut and packaged produce in a clean refrigerator with the temperature set to 40°F or colder.
  • Use separate cutting boards and utensils for produce and for raw meat, poultry, seafood, and eggs. If that isn’t an option, prepare produce before working with raw meat.
  • Wash utensils, cutting boards, and kitchen surfaces with hot, soapy water after each use.
  • Cook thoroughly or throw away any produce that touches raw meat, poultry, seafood or their juices.
  • Refrigerate cooked or cut produce, including salads, within 2 hours (1 hour if the food is exposed to temperatures above 90°F, like a hot car or picnic).

Germs, Outbreaks, and Recalls

How do leafy greens get contaminated with germs?

Germs that make people sick can be found in many places, including in the soil, in the feces or poop of animals, in refrigerators, and on kitchen surfaces.

Germs can contaminate leafy greens at many points before they reach your plate. For example, germs from animal poop can get in irrigation water or fields where theexternal icon vegetables grow. Germs can also get on leafy greens in packing and processing facilities, in trucks used for shipping, from the unwashed hands of food handlers, and in the kitchen. To prevent contamination, leafy greens should be grown and handled safely at all points from farm to fork.

Read a study by CDC and partners on what we have learned from 10 years of investigating E. coli outbreaks linked to leafy greens.

How common are outbreaks linked to leafy greens?

In 2014–2018, a total of 51 foodborne disease outbreaks linked to leafy greens (mainly lettuce) were reported to CDC. Five of the 51 were multistate outbreaks that led CDC to warn the public. Among those five outbreaks, two were linked to packaged salads, two were linked to romaine lettuce, and one could not be linked to a specific type of leafy greens.

Most recently, in 2019–2021, CDC investigated and warned the public about nine multistate outbreaks linked to leafy greens. Among those outbreaks, six were linked to packaged salads, one was linked to romaine lettuce, one was linked to baby spinach, and one could not be linked to a specific type of leafy greens. Learn about these outbreaks.

Most foodborne illnesses are not part of a recognized outbreak. The nearly 2,000 illnesses reported in 2014–2020 outbreaks linked to leafy greens represent only a small part of illnesses caused by contaminated leafy greens during those years.

Does CDC warn the public about every foodborne disease outbreak?

No. CDC does not warn the public about every foodborne outbreak—including ones linked to leafy greens. Some reasons for this include:

  • Most sources of foodborne outbreaks are never identified.
  • By the time a source is identified, it might no longer be in stores, restaurants, or homes. This can happen with foods that are perishable (foods that spoil or go bad quickly), such as leafy greens.
  • Most outbreaks affect people in only one state, so local or state health departments lead the work to identify, investigate, and communicate about those outbreaks. CDC typically communicates only about outbreaks that affect people in more than one state.

Investigating outbreaks linked to leafy greensexternal icon can be especially challenging. These outbreaks often go unidentified or unsolved.

What should I do with leafy greens that are part of a recall?

  • Never eat, serve, or sell food that has been recalled, even if some of it was eaten and no one got sick.
  • Return the recalled food to the store or throw it away at home.
    • Throw out the recalled food and any other foods stored with it or that touched it.
    • Put it in a sealed bag in an outside garbage can with a tight lid (so animals cannot get to it).
    • If the recalled food was stored in a reusable container, wash the container in the dishwasher or with hot, soapy water.
  • Follow CDC’s instructions for cleaning your refrigerator after a food recall.

Organic, Hydroponic, and Home-Grown Leafy Greens

Are organic leafy greens less likely to be contaminated than non-organic ones?

All kinds of produce, including organic leafy greens, can be contaminated with harmful germs at any point from farm to fork. CDC is not aware of any evidence that organic greens are safer.

Learn about some outbreaks linked to organic foodsexternal icon.

Are hydroponic or greenhouse-grown leafy greens less likely to be contaminated?

Leafy greens grown using these methods also can be contaminated with harmful germs at any point from farm to fork.

Learn about an outbreak linked to greenhouse-grown leafy greens.

How do I keep leafy greens in my garden safe to eat?

Home gardens can be an excellent source of fruits and vegetables. Follow these tips to help prevent food poisoning:

  • Plant your garden away from animal pens, compost bins, and manure piles.
  • Water your garden with clean, drinkable water.
  • Keep dirty water, including storm runoff, away from the parts of plants you will eat.

Learn about raised bed gardening pdf icon[PDF – 1 page].

Looking to the Future

What steps are industry and the government taking to make leafy greens safer?

CDC is collaborating with FDA, academia, and industry to investigate the factors that contribute to leafy greens contamination.

The leafy greens industry, FDA, and state regulatory authorities have been implementing provisions of the Produce Safety Ruleexternal icon as part of the FDA Food Safety Modernization Act (FSMA).external icon They are considering what further measures can be taken. FDA’s 2020 Leafy Greens STEC Action Planexternal icon describes the agency’s plans to work with partners to make leafy greens safer.

Research – What Is Cyclospora?

Food Poisoning News

Cyclospora cayetanensis is a protozoan parasite that causes the diarrheal illness known as cyclosporiasis. People acquire this infection by consuming food or water contaminated with feces containing Cyclospora. Cyclosporiasis was not previously a reportable disease in the U.S., so its rise in prevalence is due in large part to the increased availability of tests that can detect Cyclospora. It is now a nationally notifiable disease, so physicians are required to report cases of this infection.

The first three cases of cyclosporiasis were reported in 1977 and 1978, but the parasite that was causing the illnesses could not at that time be identified as Cyclospora cayetanensis; it was not until 1979 that the correct identification was made.

Norway – Cyclospora, Toxoplasma and Cryptosporidium detected in berries sold in Norway

Fresh Plaza

water contamination

Cyclospora, toxoplasma and cryptosporidium have been detected in berries sold in Norway. Blueberries, strawberries and raspberries were tested for Echinococcus multilocularis, Toxoplasma gondii, Cyclospora cayetanensis and Cryptosporidium. Raspberries were the most contaminated, followed by strawberries and blueberries. Strawberries and raspberries were mainly tainted with Cryptosporidium, while blueberries were contaminated mostly with Cyclospora. Toxoplasma and Cyclospora were frequently found in raspberries, according to the study published in the journal Food Microbiology.

However, researchers said it was important to note that only DNA was detected, so there is no certainty that the intact, infective stages of parasites were present, and there is no information on viability.

In Norway, because of the short growing season, many berries come from abroad, with more than 13,000 tons imported in 2020. In total, 86 berry samples were from domestic fruit while others came from countries such as Peru, Morocco, Chile, Netherlands, Portugal and Poland.

Researchers said that while findings are cause for some degree of concern for Norwegian food safety authorities, encouraging consumers to wash berries before consumption could reduce the risk of infection.

Research -Surveillance of berries sold on the Norwegian market for parasite contamination using molecular methods

Science Direct

water contamination

The risk of foodborne parasite infection linked to the consumption of contaminated fresh produce has long been known. However, despite epidemiological links between the outbreaks and contaminated berries, few studies have assessed the magnitude of parasite contamination on fresh produce sold in Europe. The present study was aimed to address the knowledge gap on parasite contamination of berries sold in Norway. Samples of blueberries, strawberries, and raspberries were analysed by multiplex qPCR for detection of Echinococcus multilocularisToxoplasma gondii, and Cyclospora cayetanensis. In addition, a simplex qPCR method was employed for detecting contamination of the berries with Cryptosporidium spp. A total of 820 samples of berries, each of around 30 g (274 samples of blueberries, 276 samples of raspberries, and 270 samples of strawberries), were analysed. We found an overall occurrence of 2.9%, 6.6%, and 8.3% for T. gondii, C. cayetanensis, and Cryptosporidium spp., respectively, whereas E. multilocularis was not detected from any of the samples investigated. Strawberries and raspberries were most often contaminated with Cryptosporidium spp., whereas blueberries were contaminated mostly with C. cayetanensis. Detection of parasite contaminants on fresh berries indicates the need for a system to ensure the parasitological safety of fresh berries.

CPS – Funded Research Projects 2022 – Cyclospora

220px-Cyclospora_cayetanensis_stained

CPS

Cyclospora cayetanensis monitoring in agricultural water

The parasite Cyclospora Cayetanensis is producing illness in people consuming infected produce. Because this pathogen is in very low concentrations on actual produce, which makes it close to impossible to detect, and for prevention reasons, it is more effective to check for its presence in irrigation water, from where it is typically transferred on produce. However, even in water, this parasite is very difficult to detect. It only can be detected by lengthy molecular laboratory procedures such as PCR. One major problem for scientists to develop better and faster detection methods is the fact that there is no antibody or other recognition molecule that would be able to bind to the surface of this intact parasite.

We propose to design and synthesize, for the first time, aptamers, molecules that will be able to bind to intact Cyclospora Cayetanensis oocysts, and use them to design simple paper based colorimetric tests that can detect it in the field without the need of sample preparation or specialized laboratories. The paper based test will turn from pink to purple to indicate the water sample being tested is positive for this parasite, making this a very simple and easy to use detection method for Cyclospora Cayetanensis.

CPS

AFECCT: Assessing filtration efficacy for Cyclospora control

The reputation of growers and the health of consumers suffer when people contract foodborne illness from fresh produce contaminated with Cyclospora cayetanensis. Because filtration has been established as effective in concentrating parasites for environmental surveillance, we propose to establish how effectively filters remove such parasites from irrigation water. To achieve this, we will first conduct a series of filtration experiments using abundant parasites (of chickens) that pose no risk to the study team. We’ll then assess how well these filters reduce water contamination with Cyclospora. We will also determine whether any parasites surviving filtration are harmed in the process. We hope these findings will directly benefit growers seeking tools to mitigate risk, and hasten future research progress by validating a needed surrogate system for studying other interventions against this dangerous and enigmatic human parasite.

 

USA – Domestically Acquired Cases of Cyclosporiasis — United States, May–August 2021

CDC

cardcyclosporasme

LAST UPDATED SEPTEMBER 30, 2021 4:00 PM EDT

Cyclosporiasis illnesses are reported year-round in the United States. However, during the spring and summer months there is often an increase in cyclosporiasis acquired in the United States (i.e., “domestically acquired”). The exact timing and duration of these seasonal increases in domestically acquired cyclosporiasis can vary, but reports tend to increase starting in May. In previous years the reported number of cases peaked between June and July, although activity can last as late as September. The overall health impact (e.g., number of infections or hospitalizations) and the number of identified clusters of cases (i.e., cases that can be linked to a common exposure) also vary from season to season. Previous U.S. outbreaks of cyclosporiasis have been linked to various types of fresh produce, including basil, cilantro, mesclun lettuce, raspberries, and snow peas.

At a Glance
  • Illnesses: 1020
  • Hospitalizations: 70
  • Deaths: 0
  • States reporting cases: 36

CDC, along with state and federal health and regulatory officials, monitor cases of cyclosporiasis in the United States in the spring and summer months to detect outbreaks linked to a common food source. However, many cases of cyclosporiasis cannot be directly linked to an outbreak, in part because of the lack of validated laboratory “fingerprinting” methods needed to link cases of Cyclospora infection. Officials use questionnaires to interview sick people to determine what they ate in the 14-day period before illness onset. If a commonality is found, CDC and partners work quickly to determine if a contaminated food product is still available in stores or in peoples’ homes and issue advisories.

Final Update

  • In 2021, multiple outbreaks of cyclosporiasis cases associated with different restaurants or events were investigated by state public health authorities, CDC, and FDA.
    • CDC investigated two large multistate outbreaks of cyclosporiasisexternal icon, one including 40 illnesses and one with 130 illnesses, in which ill people reported eating various types of leafy greens. State officials and FDA conducted traceback investigations for these two outbreaks, but a specific type or grower of leafy greens was not identified as the source of either outbreak.
  • As of September 28, 2021, 1,020 laboratory-confirmed cases of cyclosporiasis in people who had no history of international travel during the 14-day period before illness onset have been reported to CDC by 37 jurisdictions, including 36 states and New York City, since May 1, 2021.
    • The median illness onset date is June 25, 2021 (range: May 1–August 31, 2021).
    • At least 70 people have been hospitalized; no deaths have been reported.

September 30, 2021

Geographic Distribution of Reported Cases of Domestically Acquired Cyclosporiasis—May 1 to August 31, 2021*

outbreak_map_season_9_30_21

* Data are current as of 09/28/2021 (9:00am EDT). States/jurisdictions highlighted on the map have each reported at least one case. New York State includes case reports from New York City. Data are preliminary and subject to change. For questions related to the number of cases reported in each state, contact that state’s health department.

USA – Cyclospora cases top 1000 in the US, 36 states reporting cases

Outbreak News Today

The Centers for Disease Control and Prevention (CDC) reported 156 additional Cyclospora cases in the past month, putting the total cases since May 2021.

The 1,020 laboratory-confirmed cases of cyclosporiasis were reported in people who had no history of international travel during the 14-day period before illness onset. Cases have been reported in 37 jurisdictions, including 36 states and New York City.

Seventy people required hospitalization for their illness.

USA- Decreased Incidence of Infections Caused by Pathogens Transmitted Commonly Through Food During the COVID-19 Pandemic — Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 2017–2020

CDC

Summary

What is already known about this topic?

Before 2020, the incidence of infections transmitted commonly by food had not declined for many years.

What is added by this report?

During 2020, FoodNet identified 26% fewer infections compared with the average annual number during 2017–2019, including decreased infections associated with international travel.

What are the implications for public health practice?

The pandemic and resulting public health response present challenges to explaining changes in observed foodborne illness incidences. Continued surveillance might help elucidate the impact of the COVID-19 pandemic on foodborne illness and identify strategies to decrease illnesses. Concerted efforts are needed to reduce the incidence of these infections from farm to processing plant to restaurants and homes. Consumers can reduce their risk of foodborne illness by following safe food-handling and preparation recommendations.

Foodborne illnesses are a substantial and largely preventable public health problem; before 2020 the incidence of most infections transmitted commonly through food had not declined for many years. To evaluate progress toward prevention of foodborne illnesses in the United States, the Foodborne Diseases Active Surveillance Network (FoodNet) of CDC’s Emerging Infections Program monitors the incidence of laboratory-diagnosed infections caused by eight pathogens transmitted commonly through food reported by 10 U.S. sites.* FoodNet is a collaboration among CDC, 10 state health departments, the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS), and the Food and Drug Administration. This report summarizes preliminary 2020 data and describes changes in incidence with those during 2017–2019. During 2020, observed incidences of infections caused by enteric pathogens decreased 26% compared with 2017–2019; infections associated with international travel decreased markedly. The extent to which these reductions reflect actual decreases in illness or decreases in case detection is unknown. On March 13, 2020, the United States declared a national emergency in response to the COVID-19 pandemic. After the declaration, state and local officials implemented stay-at-home orders, restaurant closures, school and child care center closures, and other public health interventions to slow the spread of SARS-CoV-2, the virus that causes COVID-19 (1). Federal travel restrictions were declared (1). These widespread interventions as well as other changes to daily life and hygiene behaviors, including increased handwashing, have likely changed exposures to foodborne pathogens. Other factors, such as changes in health care delivery, health care–seeking behaviors, and laboratory testing practices, might have decreased the detection of enteric infections. As the pandemic continues, surveillance of illness combined with data from other sources might help to elucidate the factors that led to the large changes in 2020; this understanding could lead to improved strategies to prevent illness. To reduce the incidence of these infections concerted efforts are needed, from farm to processing plant to restaurants and homes. Consumers can reduce their risk of foodborne illness by following safe food-handling and preparation recommendations.

FoodNet conducts active, population-based surveillance of laboratory-diagnosed infections caused by Campylobacter, Cyclospora, Listeria, Salmonella, Shiga toxin-producing Escherichia coli (STEC), Shigella, Vibrio, and Yersinia reported from 10 sites covering approximately 15% of the U.S. population (approximately 50 million persons per U.S. Census Bureau estimates in 2019). Bacterial infections are defined as isolation of bacteria from a clinical specimen by culture or detection of pathogen antigen, nucleic acid sequence, or, for STEC, Shiga toxin or Shiga toxin genes by a culture-independent diagnostic test (CIDT).§ Listeria infections are defined as isolation of L. monocytogenes or detection of its nucleic acid sequences from a normally sterile site, or from placental or fetal tissue in the instance of miscarriage or stillbirth. Cyclospora infections are defined as detection of the parasite using ultraviolet fluorescence microscopy, specific stains, or polymerase chain reaction.

In this analysis, patients with no history of international travel or unknown travel were considered to have domestically acquired infection. Death was attributed to infection when it occurred during hospitalization or within 7 days after specimen collection for non-hospitalized patients. Incidence (cases per 100,000 population) was calculated by dividing the number of infections in 2020 by the U.S. Census estimates of the surveillance area population for 2019. Incidence measures included all laboratory-diagnosed infections. A negative binomial model with 95% confidence intervals (CIs) was used to estimate change in incidence during 2020 compared with those during 2017–2019, adjusting for changes in the population over time.

Surveillance for physician-diagnosed post-diarrheal hemolytic uremic syndrome (HUS), a complication of STEC infection characterized by renal failure, thrombocytopenia, and microangiopathic anemia, was conducted through a network of nephrologists and infection preventionists and by hospital discharge data review. This report includes HUS data for children aged <18 years for 2019, the most recent year for which data are available. FoodNet surveillance activities were reviewed by CDC and were conducted consistent with applicable federal law and CDC policy.**

During 2020, FoodNet identified 18,462 cases of infection, 4,788 hospitalizations, and 118 deaths (Table). The overall incidence was highest for Campylobacter (14.4 per 100,000 population), followed by Salmonella (13.3), STEC (3.6), Shigella (3.1), Yersinia (0.9), Vibrio (0.7), Cyclospora (0.6), and Listeria (0.2). During 2020, 26% fewer infections were reported compared with the average annual number reported during 2017–2019; the incidence in 2020 was significantly lower for all pathogens except Yersinia and Cyclospora. The percentage of infections resulting in hospitalization increased 2% compared with 2017–2019 (Figure 1). During 2020, 5% (958) of infections were associated with international travel compared with 14% during 2017–2019. In 2020, most (798; 83%) of these infections occurred during January–March.

Overall, 59% of bacterial infections were diagnosed using a CIDT (range = 14% [Listeria] to 100% [STEC]); this was a 2% increase from 2017−2019. The percentage diagnosed using only a CIDT (i.e., including specimens with negative cultures and those not cultured) was 1% higher during 2020 than the percentage during 2017−2019. Among specimens with a positive CIDT result during 2020, a reflex culture†† was performed for 73%, which was 2% lower than during 2017–2019. Reflex cultures decreased for Vibrio (by 15%), Yersinia (7%), Campylobacter (5%), and STEC (2%); increased for Salmonella (2%), and Shigella (2%); and did not change for Listeria.

Among 5,336 (91%) fully serotyped Salmonella isolates in 2020, the seven most common serotypes were Enteritidis (1.6 per 100,000 population), Newport (1.5), Javiana (1.0), Typhimurium (0.9), I 4,[5],12:i:- (0.5), Hadar (0.4), and Infantis (0.3). Compared with 2017–2019, incidence during 2020 was significantly lower for I 4,[5],12:i:- (48% lower), Typhimurium (37% lower), Enteritidis (36% lower), and Javiana (31% lower). Incidence was significantly higher for Hadar (617% higher; 95% CI = 382–967) and did not change significantly for Newport or Infantis. Most (73%) of the 631 outbreak-associated Salmonella infections during 2020 were caused by three serotypes: Newport (220; 35%), Hadar (135; 21%), and Enteritidis (108; 17%). All outbreak-associated Hadar infections were from one multistate outbreak linked to contact with backyard poultry; 47 (35%) illnesses resulted in hospitalization. Four serogroups accounted for 63% of the 955 culture-positive STEC isolates. Serogroup O157 was most common (264; 28%), followed by O26 (148; 15%), O103 (115; 12%), and O111 (78; 8%).

FoodNet identified 63 cases of post-diarrheal HUS in children aged <18 years (0.6 cases per 100,000 population) during 2019; 55 (87%) had evidence of STEC infection and 41 (65%) were in children aged <5 years (1.4 per 100,000 population). These rates were similar to those during 2016–2018.