Questions and Answers about the 2012 FoodNet MMWR
Questions about this report
1. What is the MMWR article "Incidence and Trends of Infection with Pathogens Transmitted Commonly Through Food – Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 1996-2012" about?
Foodborne illnesses are an important public health problem in the United States. This MMWR article, entitled “Incidence and Trends of Infection with Pathogens Transmitted Commonly Through Food — Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 1996–2012,” is an annual summary of data collected through the Foodborne Diseases Active Surveillance Network (FoodNet). FoodNet collects information to track rates and determine trends for Campylobacter, Cryptosporidium, Cyclospora, Listeria, Salmonella, Shiga toxin-producing Escherichia coli (STEC) O157 and non-O157, Shigella, Vibrio, and Yersinia infections diagnosed by laboratory testing of samples from patients, and for physician-diagnosed hemolytic uremic syndrome (HUS). It is a collaborative program among CDC, 10 state health departments, the US Department of Agriculture's Food Safety and Inspection Service (USDA-FSIS), and the Food and Drug Administration (FDA). This report summarizes 2012 preliminary surveillance data and describes trends since 1996; the information contributes to our understanding of the human health impact of foodborne diseases.
2. What are the main take-home points of the report?
- FoodNet provides accurate counts of the frequency of diagnosed infections. In 2012, FoodNet identified 19,531 laboratory-confirmed cases of infection, 4,563 hospitalizations, and 68 deaths among 48 million residents of 10 states (15% of the US population).
- The most frequent infection was caused by Salmonella accounting for 40% of reported infections, and the second by Campylobacter (35%).
- The incidence of infection caused by nearly all pathogens tracked were highest among either children aged <5 years or among older adults aged ≥65 years.
- Persons aged ≥65 years are at greater risk than younger persons for hospitalization and death related to most of the infections under FoodNet surveillance.
- FoodNet provides the best information we have on trends in specific foodborne illnesses. Comparison of incidence rates in 2012 with incidence rates in 2006–2008 shows some clear short-term changes:
- Incidence of Campylobacter infection was 14% higher. Campylobacter was the second most common infection reported in FoodNet (14.3 cases reported per 100,000 population).
- Incidence of Vibrio infection was 43% higher. Vibrio infections are rare (0.41 cases reported per 100,000 population).
- But most rates in 2012 did not change in comparison with rates in 2006–2008:
- The incidence of laboratory-confirmed Listeria, Salmonella, Shiga toxin-producing Escherichia coli (STEC) O157, and Yersinia infections did not change significantly.
- As a group, the incidence of infection with six key pathogens transmitted commonly through food (Campylobacter, E. coli O157, Listeria, Salmonella, Vibrio, and Yersinia) was unchanged.
- In 2011, the incidence of HUS was 44% lower among children aged <5 years and 29% lower among children aged <18 years compared with rates from 2006–2008 (complete HUS case detection lags behind the rest of FoodNet surveillance).
- In comparison with the first three years of FoodNet surveillance (1996–1998), long-term changes were observed:
- Declines in the incidence of infections caused by Campylobacter, Listeria, STEC O157, Shigella, and Yersinia in the early part of the decade were sustained.
- The incidence of Vibrio infection was 116% higher.
- As a group, the incidence of infection with six key foodborne pathogens (Campylobacter, Listeria, Salmonella, STEC O157, Vibrio, and Yersinia) was 22% lower. However, the incidence of Salmonella was unchanged.
Questions about specific infections
1. How do people get Campylobacter infections? What are the symptoms? How can they be prevented?
- Campylobacter transmission occurs through consumption of the organism in undercooked poultry and meat, unpasteurized dairy products, or other contaminated food or water. One can also be infected by direct contact with animals such as puppies, kittens, and farm animals, or their environments.
- Most people who become ill with campylobacteriosis get diarrhea, cramping, abdominal pain, and fever within two to five days after exposure to the organism. The diarrhea may be bloody and can be accompanied by nausea and vomiting. The illness typically lasts one week. Although most infections are self-limited, sequelae include arthritis and Guillain-Barré syndrome (a type of paralysis).
- To learn more about Campylobacter infections and how they can be prevented, visit the Campylobacter webpage.
2. How do people get Vibrio infections? How can they be prevented? Why have they increased in frequency?
- Vibrio infections are rare but often serious. Vibrio is a naturally occurring organism commonly found in marine and estuarine waters, including the Gulf of Mexico and the Atlantic and Pacific Oceans. Many Vibrio infections are due to eating raw oysters. The Vibrio bacteria multiply when the seawater where oysters grow is warm. As a result, these infections are most common during the warm months, when waters and oysters naturally contain high numbers of Vibrio organisms.
- Infections can be prevented by treating oysters at processing plants with heat, freezing, or high pressure. The risk of infection can be reduced by rapidly refrigerating oysters after harvest and by thorough cooking, especially when they come from warm growing waters. Continued Vibrio infections highlight the lack of implementation of these control measures.
- Not all Vibrio infections are due to oyster consumption. Some species, such as Vibrio alginolyticus, cause ear or wound infections after contact with marine or estuarine water. Vibrio vulnificus, which is usually transmitted through food, can also cause wound infections after contact with warm seawater.
- The incidence of Vibrio infection has increased in recent years. It is possible that global climate change resulting in warmer waters plays a role. To learn more about Vibrio infections and how they can be prevented, visit the Vibrio web pages.
Questions about specific groups of people
1. Why is the incidence of so many of these infections higher in young children, and what are some risk factors for these infections in young children?
The incidence of Campylobacter, Cryptosporidium, Salmonella, Shigella, STEC O157, STEC non-O157, and Yersinia infection were highest among children aged <5 years. Young children are more likely than persons in other age groups to be brought to medical attention for diarrheal illness, and this is part of the explanation. However, the immune system in young children is not fully developed, which is another reason why they are at highest risk for many infections. Studies in young children have identified various food and non-food exposures—including visiting a farm, riding in a shopping cart near raw meat or poultry, and contact with turtles, water frogs, and baby chicks —that can increase the risk of infection with these pathogens. Breastfeeding provides important protection to infants and should continue to be encouraged.
2. Why are the hospitalization and death rates for so many of these infections higher in older adults?
For infections with most pathogens under FoodNet surveillance, persons aged ≥65 years are at greater risk than are other persons for hospitalization and death, probably reflecting the fact that many older adults have other health issues that put them at higher risk for severe illness if they get one of these infections. These data highlight the need for prompt diagnosis and treatment in this age group as well as for careful attention to food safety.
Where can I go for more information on foodborne illness?
- To view the article, ‘Incidence and Trends of Infection with Pathogens Transmitted Commonly Through Food — Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 1996–2012’ in its entirety along with supplemental tables, visit the FoodNet website.
- For information on past reports, visit the Reports page of the FoodNet website.
- For information on foodborne disease prevention and current activities, visit the CDC's Food Safety and the Food Safety.gov websites.
- For information on the new Food Safety Modernization Act and CDC’s role, visit the Food Safety Modernization Act web page.
- For information on what consumers can do to reduce the risk for foodborne illness, visit the CDC’s Food Safety, the Food Safety.gov, and the Fight Bac websites.