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

What You Need To Know About Infectious Disease

Foodborne Pathogens

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 48 million Americans—about one in six—become infected by what they eat. Approximately 128,000 are hospitalized and about 3,000 (8 each 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. Based on 2013 trend data, the Centers for Disease Control and Prevention (CDC) highlighted the need to develop preventive measures. Steps include supporting Centers of Excellence, often the first facilities to respond to outbreaks; developing and sharing next-generation DNA sequencing among all the states; improving the integration of foodborne illnesses surveillance systems; and expanding data sharing among private businesses, health care systems, and local, state, and federal health agencies.
The Pathogens Behind Foodborne Illness
Foodborne disease occurs when a susceptible host consumes contaminated foods or beverages. Many different disease-causing microorganisms—bacteriaviruses, 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 several kinds of bacterial infections. Campylobacter is the most frequently identified bacterial cause of diarrheal illness in the world. Salmonella spreads to humans through a variety of foods of animal origin, or through fecal contamination; the latter is what caused the 2015 meat-product outbreak from E. coli 026, which affected Chipotle restaurants in nine states. E. coli, though a serious bacterial illness, is   not as virulent as the most potent strain of this infection, E. coli O157:H7. This is the agent behind a serious and sometimes deadly complication called hemolytic-uremic syndrome (HUS). Another bacterial pathogen, Listeria monocytogenes, often found in produce, sickened 147 people in 28 states, resulting in 43 deaths. This 2011 outbreak was attributed to tainted cantaloupes. 
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 Vibrio cholerae, 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.
However, not all foodborne pathogens require an incubation period. 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 complex food economy, opportunities abound for an ingredient that has come into contact with pathogens to contaminate a batch of food and be shipped widely and rapidly. Meat and poultry carcasses can become contaminated during slaughter by contact with small amounts of intestinal contents and be used in large batches of processed food. In particular, meat consumption has increased steadily during the past three decades, with nearly 30 billion food animals produced in 2010. This demand results in more contact between humans and animals, increasing the chances for contamination. 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 now account for almost half of all outbreaks.) 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.
Protecting the Food Supply
As active players in the international marketplace, developing countries must bolster their regulatory systems to help safeguard the world’s food supply. To this end, international and intergovernmental organizations can work with these countries to help them attend international meetings, including those standardizing best practices in food safety.
Other ways to protect the food supply include working more closely with countries with stringent regulations in place, sharing inspection reports, and cooperating with the World Health Organization (WHO) and other international agencies as they strengthen surveillance systems. 
How to Protect Yourself
Consumers can reduce the risk of foodborne illness by adhering to the following safe food handling and preparation practices:
Wash: Before handling food, wash your hands with soap and warm water, washing for at least 20 seconds while rubbing hands together.
Cook: Thoroughly cook meat, poultry, and eggs. 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 your 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: If you suspect any foodborne illness report it to your local health department.

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What do you know about infectious disease?

True or False: Infection with a pathogen (a disease-causing microbe) does not necessarily lead to disease.

  • Correct!

    Infection occurs when viruses, bacteria, or other microbes enter your body and begin to multiply. Disease follows when the cells in your body are damaged as a result of infection, and signs and symptoms of an illness appear.

  • Sorry, that’s incorrect.

    Infection occurs when viruses, bacteria, or other microbes enter your body and begin to multiply. Disease follows when the cells in your body are damaged as a result of infection, and signs and symptoms of an illness appear.

Infectious Disease Defined


A close relationship between two organisms in which one organism, the parasite, benefits at the expense of the host organism.

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