Epidemiology of Foodborne Disease

ENVR 421

Mark D. Sobsey

Foodborne Disease Outbreaks 1998-2002

• For majority of outbreaks food was eaten outside the home

• Restaurants were the most commonly reported place where food was eaten.

• Many outbreaks caused by Salmonella or norovirus occurred at a school or nursing home.

• For outbreaks caused by ciguatoxin and L. monocytogenes, food was more commonly reported to have been eaten at a private home

FBDOs 1998-2002, Cont’d.• Notable outbreaks were caused by ground beef contaminated with E.

coli O157:H7 and fresh produce contaminated with Salmonella, E. coli O157:H7, Cyclospora cayetanensis, or hepatitis A

• Multidrug-resistant strains of Salmonella caused outbreaks linked to unpasteurized milk and ground beef.

• A large multistate outbreak of listeriosis caused by contaminated deli meat led to one of the largest food recalls in the United States.

• Scombrotoxin (fish-derived histaminic agent) caused the majority of outbreaks attributable to a chemical etiology. – Majority of outbreaks associated with tuna, – Some from with nonscombroidae fish, including 10 by escolar

• Unexpected vehicles of transmission: dry cereal, parsley and mangoes

FBDOs, 1998-2002, Cont’d.

• Norovirus caused 657 (30%) of the 2,167 FBDOs with a known etiology and 39% of all outbreak-related cases in these outbreaks.

• S. Enteritidis: most frequent bacterial cause of FBDOs – Caused 204 outbreaks – Accounted for 9% of OBs for which etiology was determined– Eggs caused more S. Enteritidis OB than any other food

• L. monocytogenes resulted in 38 outbreak-related deaths among 256 cases, – more deaths, and a higher case-fatality rate (15%) than

any other pathogen

Foodborne Disease in The USA: 1993-1997

• Bacterial pathogens caused most outbreaks/infections with a known etiology

• But, 68% of reported FBDOs were of unknown etiology– Need improved epidemiologic and lab investigations.– ~ 50% had incubations period of >15 hours, suggesting viral

etiology. Viruses (e.g., Norwalk-like viruses) are likey a much more important cause of foodborne disease outbreaks than is currently recognized.

– Local and state public health lack resources and expertise to diagnose viral pathogens, but the methods are now increasingly available in some state laboratories.

– Viral outbreaks are more likely to detected in the future.

Foodborne Disease in the Home

• About half of all Salmonella cases result from unsafe handling of food in the home.

• Foodborne illness costs the United States $23 billion annually.

• Foodborne illness is often mistaken for “the flu, as many of the symptoms are similar:– stomach pain, diarrhea, nausea, chills, fever, and

headache.• Many experts believe the kitchen is home to

more potentially dangerous bacteria than even the bathroom.

Foodborne Disease in The USA: 1993-1997FBDOs with a known etiology:• multistate outbreaks caused by contaminated produce and outbreaks

caused by E. coli O157:H7 remained prominent. • S. enteritidis remains a major cause of illness and death.

– ~40% of persons who died from S. enteritidis were residents of nursing homes.

– Seriousness of S. enteritidis in elderly persons, many of whom might be immunocompromised.

– Decrease risks for egg-associated infections of S. enteritidis by not eating raw or undercooked eggs.

– Nursing homes, hospitals, and commercial kitchens should use pasteurized egg products for all recipes requiring pooled or lightly cooked eggs. Proper egg storage in homes.

• Several outbreaks involved imported food items, emphasizes the role of food production and distribution in FBDOs.

Foodborne Disease Burden in the Unites States

• Estimated 76 million illnesses and 5,000 deaths each year.

• Foodborne diseases are common, but only a fraction of these illnesses are routinely reported to CDC– Passive surveillance system– Many diseases not reportable– a complex chain of events must occur to report a

foodborne infection to CDC– Most household foodborne infection are not

recognized or reported

Salmonella Infection

• Causes an estimated 1.4 million foodborne illnesses/year

• From 1993-1997, only 189,304 Salmonella infections (~38,00/year) reported through the National Salmonella Surveillance System– a passive, laboratory-based system.

• In the same period, 357 recognized outbreaks of Salmonella infection resulting in 32,610 illnesses were reported through the Foodborne-Disease Outbreak Surveillance System.

• These system greatly underestimate the burden of foodborne disease.

Active Surveillance Network for Foodborne Disease in the United States: FoodNet

• Foodborne disease component of the CDC's Emerging Infections Program (EIP).

• Established in 1995• Collaborative project among CDC, several EIP sites (states

cities and territories), U.S. Department of Agriculture (USDA), and the U.S. Food and Drug Administration (FDA).

• Consists of active surveillance for foodborne diseases and• related epidemiologic studies designed to help public health

officials better understand the epidemiology of foodborne diseases in the United States.

FoodNet Surveillance Sites

FoodNet Surveillance States: California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon, Tennessee

• Principal foodborne disease component of CDC's Emerging Infections Program (EIP).

• Collaborative project of CDC, 10 EIP sites, U.S. Department of Agriculture (USDA), and Food and Drug Administration (FDA)

• Consists of active surveillance for foodborne diseases and related epidemiologic studies designed to help public health officials better understand foodborne disease epidemiology in the USA

FoodNet Program

Tracks foodborne illness using:

• surveys of physicians and laboratories,

• case-control studies• active case finding of

targeted pathogens

Targeted Pathogens:

Bacteria:• Campylobacter • E. coli O157 • Listeria • Salmonella• Shigella • Vibrio • Yersinia

Parasites:• Cryptosporidium• Cyclospora

FoodNet Website:

http://www.cdc.gov/foodnet/default.htm

Goals of FoodNet

• Describe the epidemiology of new and emerging bacterial, parasitic, and viral foodborne pathogens

• Estimate the frequency and severity of foodborne diseases that occur.

• Determine how much foodborne illness results from eating specific foods, such as meat, poultry, eggs produce, etc.

Components of FoodNet

• Active laboratory-based surveillance

• Survey of clinical laboratories

• Survey of physicians

• Survey of the population

• Epidemiologic Studies

Water- and Foodborne Illness Surveillance in Other Countries

• Efforts vary from country to country• Most have little if any surveillance• Some have more active and integrated

surveillance than in the United States– National health care systems– Integrated laboratories– Subsidized laboratory analyses– Other incentives

• political, social, etc.

Laboratory Reports of Gastrointestinal Infections in England and Wales

Overview of Communicable Diseases England and Wales - Priorities