v Bacteria and Foodborne Illness

Foodborne illness results from eating food contaminated with bacteria (or their toxins) or other pathogens such as parasites or viruses. The illnesses range from upset stomach to more serious symptoms, including diarrhea, fever, vomiting, abdominal cramps, and dehydration. Although most foodborne infections are undiagnosed and unreported, the Centers for Disease Control and Prevention estimates that every year about 76 million people in the United States become ill from pathogens in food. Of these, about 5,000 die.

Causes

Harmful bacteria are the most common causes of foodborne illnesses. Some bacteria may be present on foods when you purchase them. Raw foods are not sterile. Raw meat and poultry may become contaminated during slaughter. Seafood may become contaminated during harvest or through processing. One in 20,000 eggs may be contaminated with Salmonella inside the egg shell. Produce such as lettuce, tomatoes, sprouts, and melons can become contaminated with Salmonella, Shigella, or Escherichia coli (E. coli) O157:H7. Contamination can occur during growing, harvesting, processing, storing, shipping, or final preparation. Sources of contamination are varied; however, these items are grown in the soil and therefore may become contaminated during growth or through processing and distribution. Contamination may also occur during food preparation in the restaurant or in the person’s kitchen.

When food is cooked and left out for more than 2 hours at room temperature, bacteria can multiply quickly. Most bacteria grow undetected because they do not produce an "off" odor or change the color or texture of the food. Freezing food slows or stops bacteria’s growth but does not destroy the bacteria. The microbes can become reactivated when the food is thawed. Refrigeration may slow the growth of some bacteria, but thorough cooking is needed to destroy the bacteria.

Symptoms

In most cases of foodborne illness, symptoms resemble intestinal flu and may last a few hours or even several days. Symptoms can range from mild to serious and include 

• abdominal cramps

• nausea

• vomiting

• diarrhea

• fever

• dehydration

Risk Factors

Some people are at greater risk for bacterial infections because of their age or immune status. Young children, pregnant women and their fetuses, the elderly, and people with lowered immunity are at greatest risk.

Complications 

Some micro-organisms, such as Listeria monocytogenes and Clostridium botulinum, cause far more serious illness than vomiting or diarrhea. They can cause spontaneous abortion or death.

In some people, especially children, hemolytic uremic syndrome (HUS) can result from infection by a particular strain of bacteria, E. coli O157:H7, and can lead to kidney failure and death. HUS is a rare disorder that affects primarily young children between the ages of 1 and 10 years and is the leading cause of acute renal failure in previously healthy children. The child may become infected after consuming a contaminated food, such as meat (especially undercooked ground beef), unpasteurized apple cider or apple juice, or raw sprouts.

The most common symptoms of infection are vomiting, abdominal pain, and diarrhea, which may be bloody. In 5 to 10 percent of cases, HUS develops about 2 to 6 days after the onset of illness. This disease may last from 1 to 15 days and is fatal in 3 to 5 percent of cases. Symptoms of HUS include fever, lethargy, irritability, and pallor. In about half the cases, the disease progresses until the kidneys are unable to remove waste products from the blood and excrete them into the urine (acute renal failure). A decrease in circulating red blood cells and blood platelets and reduced blood flow to organs may lead to multiple organ failure. Seizures, heart failure, inflammation of the pancreas, and diabetes can also result. However, most children recover completely. 

You need to see a doctor right away if you have any of the following symptoms, with or without gastrointestinal symptoms:

Diagnosis 

Your doctor may be able to diagnose foodborne illness from a list of what you’ve recently eaten and results from the proper laboratory tests. Diagnostic tests for foodborne illness should include examination of the feces. A sample of the suspected food, if available, can also be tested for bacteria and their toxins as well as for viruses and parasites.

Treatment

Most cases of foodborne illness are mild and can be treated by increasing fluid intake, either orally or intravenously, to replace lost fluids and electrolytes. In cases with gastrointestinal or neurologic symptoms, people should seek medical attention.

In the most severe situations, such as HUS, the patient may need hospitalization in order to receive supportive nutritional and medical therapy. Maintaining adequate fluid and electrolyte balance and controlling blood pressure are important. Doctors will try to minimize the impact of reduced kidney function. Early dialysis is crucial until the kidneys can function normally again, and blood transfusions may be needed.

Prevention

Most cases of foodborne illness can be prevented through proper cooking or processing of food, which kills bacteria. In addition, because bacteria multiply rapidly between 40°F and 140°F, food must be kept out of this "danger zone."

To prevent harmful bacteria from growing in food, always 

Food Irradiation

Food irradiation is the treatment of food with high energy such as gamma rays, electron beams, or x rays as a means of cold pasteurization, which destroys living bacteria, to control foodborne disease. The United States relies exclusively on the use of gamma rays, which are similar to ultraviolet light and microwaves and pass through the food leaving no residue or "radioactivity." Food irradiation is currently approved for wheat, potatoes, spices, seasonings, pork, poultry, red meats, whole fresh fruits, and dry or dehydrated products. Although irradiation destroys many bacteria, it does not sterilize food. Even if you’re using food that has been irradiated by the manufacturer, you must continue to take precautions against foodborne illness, through proper refrigeration and handling, to safeguard against any surviving organisms.

Links to Other Disorders

Scientists suspect that foodborne pathogens are linked to chronic disorders and can even cause permanent tissue or organ destruction. Research suggests that when some people are infected by foodborne pathogens, the activation of their immune system can trigger an inappropriate autoimmune response, which means the immune system attacks the body’s own cells. In some people, an autoimmune response leads to a chronic health condition. 
Chronic disorders that may be triggered by foodborne pathogens are

• arthritis 

• inflammatory bowel disease

• kidney failure

• Guillain-Barrι syndrome

• autoimmune disorders

Further research is needed to explain the link.

Common Sources of Foodborne Illness 

Source of illness: Raw and undercooked meat and poultry

Symptoms: Abdominal pain, diarrhea, nausea, and vomiting
Bacteria: Campylobacter jejuni, E. coli O157:H7, L. monocytogenes, Salmonella

Source of illness: Raw (unpasteurized) milk and dairy products, such as soft cheeses
Symptoms: Nausea and vomiting, fever, abdominal cramps, and diarrhea
Bacteria: L. monocytogenes, Salmonella, Shigella, Staphylococcus aureus, C. jejuni

Source of illness: Raw or undercooked eggs. Raw eggs may not be recognized in some foods such as homemade hollandaise sauce, caesar and other salad dressings, tiramisu, homemade ice cream, homemade mayonnaise, cookie dough, and frostings.
Symptoms: Nausea and vomiting, fever, abdominal cramps, and diarrhea
Bacteria: Salmonella enteriditis

Source of illness: Raw or undercooked shellfish
Symptoms: Chills, fever, and collapse
Bacteria: Vibrio vulnificus, Vibrio parahaemolyticus

Source of illness: Improperly canned goods, and smoked or salted fish
Symptoms: Double vision, inability to swallow, difficulty speaking, and inability to breathe (seek medical help right away!)
Bacteria: C. botulinum

Source of illness: Fresh or minimally processed produce
Symptoms: Diarrhea, nausea, and vomiting
Bacteria: E. coli O157:H7, L. monocytogenes, Salmonella, Shigella, Yersinia enterocolitica, viruses, and parasites

Points to Remember

v Viral Gastroenteritis

Viral gastroenteritis is an intestinal infection caused by several viruses. Viral gastroenteritis is highly contagious and causes millions of cases of diarrhea each year.

Anyone can get viral gastroenteritis and most people recover without any complications. However, viral gastroenteritis can be serious for people who cannot drink enough fluids to replace what is lost through vomiting and diarrhea, especially infants, young children, the elderly, and people with weak immune systems. Complications from vomiting also can occur, even in healthy people. 

Symptoms

The main symptoms of viral gastroenteritis are watery diarrhea and vomiting. Other symptoms are headache, fever, chills, and abdominal pain. The symptoms may appear within hours or a few days of infection. They usually last for 1 to 2 days, but may last as long as 10 days. 

Causes

The viruses that cause viral gastroenteritis damage the cells in the lining of the small intestine. As a result, fluids leak from the cells into the intestine and produce watery diarrhea. Four types of viruses cause most viral gastroenteritis.

Viral gastroenteritis is often mistakenly called "stomach flu," but it is not caused by the influenza virus and it does not infect the stomach. Also, viral gastroenteritis is not caused by bacteria or parasites. For information about bacterial infections, please see the Bacteria and Foodborne Illness fact sheet from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

Transmission

Viral gastroenteritis is highly contagious. The viruses are often transmitted on unwashed hands. People can get the viruses through close contact with infected individuals, such as sharing their food, drink, or eating utensils, or by eating food or drinking beverages that are contaminated with the virus. People who no longer have symptoms may still be contagious, since the virus can be found in the stool for up to 2 weeks after they recover from their illness. Also, people can become infected without having symptoms, and they can still spread the infection.

Outbreaks of viral gastroenteritis can occur in child care settings, schools, nursing homes, cruise ships, camps, dormitories, restaurants, and other places where people gather in groups. If you suspect that you were exposed to a virus in one of these settings, you may want to contact your local health department, which tracks outbreaks.

Diagnosis

If you think you have viral gastroenteritis, you may want to see your doctor, although many people don’t bother. Doctors generally diagnose viral gastroenteritis based on the symptoms and a physical examination. Your doctor may ask for a stool sample to test for rotavirus or to rule out bacteria or parasites as the cause of your symptoms. No routine tests are currently available for the other types of viruses. 

Treatment

Most cases of viral gastroenteritis resolve over time without specific treatment. Antibiotics are not effective against viral infections. The primary goal of treatment is to reduce the symptoms, and prompt treatment may be needed to prevent dehydration.

Your body needs fluids to function. Dehydration is the loss of fluids from the body. Important salts or minerals, known as electrolytes, can also be lost with the fluids. Dehydration can be caused by diarrhea, vomiting, excessive urination, or excessive sweating, or by not drinking enough fluids because of nausea, difficulty swallowing, or loss of appetite.
In viral gastroenteritis, the combination of diarrhea and vomiting can cause dehydration. The symptoms of dehydration are 

• excessive thirst 

• dry mouth 

• little or no urine or dark yellow urine 

• decreased tears 

• severe weakness or lethargy 

• dizziness or lightheadedness 

If you notice any of these symptoms, you should talk to your doctor. Mild dehydration can be treated by drinking liquids. Severe dehydration may require intravenous fluids and hospitalization. Untreated severe dehydration can be life threatening.

Children present special concerns. Because of their smaller body size, infants and children are at greater risk of dehydration from diarrhea and vomiting. Oral rehydration solutions such as Pedialyte can replace lost fluids, minerals, and salts.

You can take several steps to help relieve the symptoms of viral gastroenteritis. 

Prevention

Prevention is the only way to avoid viral gastroenteritis. There is no vaccine available. You can avoid it by 

• washing your hands thoroughly after using the bathroom or changing diapers 

• washing your hands thoroughly before eating 

• disinfecting contaminated surfaces 

• not eating or drinking foods or liquids that might be contaminated 

Points to Remember