Older Americans, pregnant women face highest risk from Listeria food poisoning

Most recent outbreaks linked to soft cheese, raw produce

Listeria can cause serious infection in certain vulnerable groups, resulting in higher rates of hospitalization and death than most other bacteria commonly spread by contaminated food. A new Vital Signs report by the Centers for Disease Control and Prevention outlines the key groups particularly hard hit by listeria food poisoning. It also highlights the importance of safety measures to prevent contamination of cheese and raw produce, such as those included in the 2011 Food Safety Modernization Act.

Adults aged 65 years and older are among the groups most affected; they are four times more likely to get listeria infection than the general U.S. population. Pregnant women are 10 times more likely get it and pregnant Hispanic women are 24 times more likely. These groups – along with newborns and people with other health conditions that weaken their immune systems – account for at least 90 percent of reported listeria infections. The Vital Signs report highlights the need to educate these groups about how to prevent listeria infections.

The Vital Signs report provides a national snapshot of 2009-2011 illness rates and foods associated with listeria outbreaks reported to CDC through three monitoring systems. Key findings include:

More than 1,650 listeria illnesses were reported to CDC over a three-year period.

About 20 percent of infections caused a death. Deaths primarily occurred among older people and as miscarriages or stillbirths. Pregnant women who have listeria infections often have only mild symptoms or fever, but their infections may result in miscarriage, premature labor and serious illness or death in newborn infants.

Over three years, twelve outbreaks sickened 224 patients in 38 states. These include the large 2011 outbreak linked to whole cantaloupes from one farm.

Of the 10 outbreaks with an identified food source, six were linked to soft cheese (mostly Mexican-style cheeses) and two to raw produce (whole cantaloupe and pre-cut celery).

“Listeria strikes hard at pregnant women, the elderly, and people with weakened immune systems, sending many to the hospital and causing miscarriage or death in as many as one in five,” said Tom Frieden, M.D., M.P.H., Director, CDC. “We need to develop new cutting edge molecular technologies to help us link illnesses and outbreaks to foods faster to prevent illness and death, which is why the President’s Budget proposes investing in new tools to advance this work.”

Since the 1990s, genetic fingerprinting of listeria through CDC’s PulseNet has helped identify many listeria outbreaks, which led to food industry and regulatory changes to help make foods like hot dogs and deli meat safer. Rates of illness fell by about 25 percent by the early 2000s; however, rates have since leveled off. The President’s FY 2014 Budget proposes an investment of $40 million for CDC’s Advanced Molecular Detection Initiative, which would strengthen the U.S. public health system’s ability to protect communities from disease and foodborne illness. Additionally, CDC has plans to test an advanced DNA fingerprinting method on listeria, called whole genome sequencing, to find and control outbreaks faster.

“The lower rates of listeria infection attributed to meat and poultry over the past decade point to the success of prevention-based policies and industry best practices,” said Elisabeth Hagen, M.D., Undersecretary for Food Safety, U.S. Department of Agriculture. “However, important work remains if we hope to continue this momentum. Additional research and continual monitoring of evolving risks will allow us to develop policies that further reduce these illness rates.”

USDA and the U.S. Food and Drug Administration recently analyzed nearly 27,000 ready-to-eat food samples from retailers to help determine the level of listeria in them. USDA, CDC and FDA also continue to work with several states to examine which handling, storing and preparation practices may lead to cross-contamination of ready-to-eat foods.

Recent outbreaks have been linked to foods not usually linked to listeria infection, which highlights new opportunities for control measures and highlights the need to identify more foods causing infection and keep listeria from entering the food supply.

“Through the 2011 Food Safety Modernization Act, FDA is developing rules aimed at preventing the introduction of Listeria and other dangerous bacteria into our food supply,” said Michael R. Taylor, Deputy Commissioner for Foods and Veterinary Medicine, FDA. “We are also working with produce growers, food processors, and our state partners to further implement what we know works to minimize food safety risks.”

CDC recommends that no one consume unpasteurized milk or soft cheese made from unpasteurized milk. Soft cheeses can be crumbly, like queso fresco, or soft and spreadable. People at higher risk for listeria infection should also be aware that some Mexican-style soft cheeses, like queso fresco, made from pasteurized milk have caused listeria illnesses, likely because of contamination during cheese making. They should always heat hot dogs and deli meat until steaming hot (165° F), and everyone should follow good food safety practices of clean, separate, cook and chill.

For more information on safely preparing and refrigerating foods prone to contamination with listeria and other foodborne germs, please visit www.cdc.gov/listeria. Advice for consumers on preventing all foodborne diseases is available at www.foodsafety.gov.

About Vital Signs

CDC Vital Signs is a report that appears on the first Tuesday of each month as part of the CDC journal Morbidity and Mortality Weekly Report (MMWR). Vital Signs is designed to provide the latest data and information on key health indicators — cancer prevention, obesity, tobacco use, alcohol use, HIV/AIDS, motor vehicle safety, health care-associated infections, cardiovascular health, teen pregnancy,  viral hepatitis, and food safety.

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U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES