The National Academies: What You Need To Know About Infectious Disease

The National Academies

What You Need To Know About Infectious Disease

Foods pooled from many sources, such as batches of raw ground beef, can become tainted if any of the meat in the batch is contaminated with a human pathogen.

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Foodborne Pathogens

Each year an estimated 76 million Americans— about one in four—become infected by what they eat. Approximately 325,000 are hospitalized. More than 5,000 (14 a day) die. The true magnitude of foodborne illness is likely to be much higher than even the official estimates because most people do not seek medical attention for its symptoms, such as abdominal cramps, vomiting, and diarrhea. In April 2009 the U.S. Centers for Disease Control and Prevention (CDC) reported that progress in reducing foodborne infections had stalled, pointing to gaps in the existing food safety system and the need to develop improved food safety practices as products move from the farm to the table.
The Pathogens Behind Foodborne Illness
Foodborne disease occurs when a susceptible host consumes contaminated foods or beverages. Many different disease-causing microorganisms—bacteria, viruses, and parasites—can taint foods and liquids, each potentially associated with a different illness.
Raw foods of animal origin are the most likely to be contaminated—that is, raw meat and poultry, raw eggs, unpasteurized milk, and raw shellfish.
The most common causes of foodborne illness include the bacterial infections Campylobacter, the most frequently identified bacterial cause of diarrheal illness in the world; Salmonella, which spreads to humans through a variety of foods of animal origin, or through fecal contamination of plant-based foods, such as in the 2009 peanut- product outbreak; and E. coli O157:H7, the agent behind a serious and sometimes deadly complication called hemolytic-uremic syndrome (HUS). The most common viral cause of foodborne illness is Calicivirus, also referred to as Norwalk-like virus or norovirus. Unlike the previous three bacterial foodborne pathogens, noroviruses easily spread from one infected person to another and can contaminate an environment, making them extremely difficult to eradicate from hotels, hospitals, nursing homes, cruise ships, and similar establishments where large numbers of people congregate.
After you swallow a foodborne pathogen there may be a delay—the incubation period—before symptoms appear. This delay may range from hours to days. During the incubation period, the microbes pass through the stomach into the intestine, attach to the cells lining the intestinal walls, and begin to multiply there. Some types of microbes stay in the intestine. Some, like cholera, produce a toxin that causes the body to secrete water, resulting in diarrhea. Others, like the typhoid bacillus, invade and replicate in the deeper body tissues.
Not all foodborne pathogens require an incubation period, however. Illness can result from toxins that form in the food before it is eaten—leading to true “food poisoning.” In such cases, bacteria do not need to replicate in the body at all and the onset of symptoms can be more rapid.
What Causes Outbreaks?
In the past few decades, food production and distribution for the developed world have increasingly involved vast and intricate global networks. This sprawling system produces food that, if contaminated, increases the potential for widespread epidemics. In this giant food economy opportunities abound for food to come in contact with pathogens. Meat and poultry carcasses can become contaminated during slaughter by contact with small amounts of intestinal contents. Fresh fruits and vegetables become tainted if they are washed or irrigated with water contaminated with animal manure or human sewage. (Outbreaks related to fresh produce have increased eightfold in the United States during the past several decades.) And increasingly, we don’t cook our own meals, leaving food safety in the hands, literally, of others.
Raw foods of animal origin are the most likely to be contaminated—that is, raw meat and poultry, raw eggs, unpasteurized milk, and raw shellfish. Foods for which such products are pooled from many sources and batch processed are also hazardous, because a pathogen present in any one of the animals might contaminate the whole batch.
How to Protect Yourself
Consumers can reduce the risk of foodborne illness by adhering to the following safe food handling and preparation practices:
Wash hands thoroughly with soap and warm water before handling food.
Cook meat, poultry, and eggs thoroughly. Use a thermometer to measure the internal temperature of meat, to be sure that it is cooked sufficiently to kill bacteria. Ground beef, for example, should be cooked to an internal temperature of 160oF. Eggs should be cooked until the yolk is firm.
Separate: Avoid cross-contaminating foods by washing hands, utensils, and cutting boards after contact with raw meat or poultry and before they touch another food. Unless it is disinfected between each use, don’t use a “universal” cleanup tool such as a sponge. Place cooked meat on a clean platter, rather than back on the one that held the raw meat.
Chill: Bacteria can grow quickly at room temperature, so refrigerate leftover foods if they are not going to be eaten within 4 hours. A large volume of food will cool more quickly if divided into several shallow containers for refrigeration.
Clean: Rinse fresh fruits and vegetables in running tap water to remove visible dirt and grime. Remove and discard the outermost leaves from a head of lettuce or cabbage. Because bacteria can grow on the cut surface of fruits or vegetables, be careful not to contaminate these foods while slicing them on a cutting board, and avoid leaving cut produce at room temperature for many hours.
Report suspected foodborne illness to your local health department.

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The human papillomavirus (HPV) causes about what percentage of cervical cancer cases?

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    The human papillomavirus (HPV) causes more than 90% of cervical cancer cases.

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    The human papillomavirus (HPV) causes more than 90% of cervical cancer cases.

  • Correct!

    The human papillomavirus (HPV) causes more than 90% of cervical cancer cases.

Infectious Disease Defined


The smallest unit of living matter capable of functioning independently.

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