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Issues: Food Safety

Pathogens and Produce

To help its members and the industry understand foodborne illnesses, below are some of the pathogens sometimes linked to food products.

Cyclospora

Cyclospora cayetanensisis a one-celled parasite that spreads through the fecal-oral route. People of all ages are at risk for infection. The risk may vary with season; some evidence suggests that infection is most common in spring and summer. Cyclospora infects the small intestine and typically causes an illness characterized by watery diarrhea. Other symptoms can include loss of appetite, weight loss, bloating, increased flatus, stomach cramps, nausea, vomiting, tiredness, muscle aches, and low-grade fever. Some people infected with Cyclospora do not develop any symptoms.

E. Coli O157:H7

Major sources of E. coli O157:H7 are ground beef and raw milk. Waterborne transmission has occurred. The organism is easily transmitted from person to person, and has been difficult to control in child day care centers. A person with E. coli O157:H7 usually has acute bloody diarrhea and abdominal cramps with little or no fever. Children under 5 years and the elderly are at greatest risk from Escherichia coli serotype O157:H7. Reported rates in developed countries are five to eight cases per 100,000 population per year; it is rarely reported in less-developed countries.

Hepatitis A

Hepatitis A is caused by the hepatitis A virus (HAV). In the past, the disease was known as infectious jaundice. The virus is hearty and survives drying and freezing. It is spread through the fecal-oral route.

Most infections of hepatitis A in the United States occur in large communitywide outbreaks caused by direct person-to-person transmission. Only about 2-3% of U.S. cases are attributable to food- or waterborne transmission, and only a few of these are traced to produce at the grower or distributor level. However, when these outbreaks do occur, they may involve hundreds of people in several states.

Most foodborne outbreaks of hepatitis A occur in restaurants or other foodservice situations. In a few instances, fruits or vegetables have become contaminated with HAV by infected pickers, packers, or processing personnel. Hepatitis A can also contaminate food through improper disposal of human waste in or near agricultural fields or irrigation water that is contaminated with human waste.

HAV infects the liver and prevents it from removing wastes and toxins from the body. Typically, the first symptoms are like the flu, followed by fever, fatigue, abdominal discomfort, nausea, vomiting, dark urine, and jaundice (yellowing of the eyes and skin).

Death from hepatitis A is rare in younger people but can reach 1-2% in those over the age of 50. Two safe and effective vaccines against hepatitis A are available on the market.

Hepatitis E

Hepatitis E is caused by the hepatitis E virus (HEV). It is clinically indistinguishable from hepatitis A disease. HEV is spread by the fecal-oral route and is usually associated with contaminated drinking water, especially common after major floods. Although there is a potential for foodborne transmission, HEV has not been isolated from foods.

Virtually all cases of acute hepatitis E in the United States have occurred among travelers returning from areas of the world where hepatitis E disease is endemic.

The disease is usually mild and resolves in 2 weeks. Typical clinical signs and symptoms are similar to those of hepatitis A and include abdominal pain, dark urine, fever, jaundice, malaise, nausea, and vomiting. The highest evidence of disease has been in young to middle-age adults. Pregnant women appear to be exceptionally susceptible to severe disease. The fatality rate is 0.1% except in pregnant women. This group is reported to have a fatality rate approaching 20%. There is no vaccine to prevent HEV.

Listeriosis

Listeriosis is caused by Listeria monocytogenes. The disease affects primarily at-risk populations, including pregnant women, newborns, and adults with weakened immune systems. Although healthy people may eat contaminated foods without becoming ill, those at increased risk for infection can probably get listeriosis after eating food contaminated with even a few bacteria.

Produce can become contaminated from the soil or from manure used as fertilizer. The bacterium has been found in a variety of raw foods, such as uncooked meats and vegetables, as well as in processed foods that become contaminated after processing, such as soft cheese and cold cuts at the deli counter. Unpasteurized milk or foods made from unpasteurized milk may contain the bacterium.

A person with listeriosis usually has fever, muscle aches, and sometimes nausea or diarrhea. If infection spreads to the nervous system, symptoms such as headache, stiff neck, confusion, loss of balance, or convulsions can occur. Infection during pregnancy can lead to premature delivery, infection of the newborn, or even stillbirth.

Listeria is killed by pasteurization, and heating procedures used to prepare ready-to-eat processed meats should be sufficient to kill the bacterium; however, unless good manufacturing practices are followed, contamination can occur after processing.

Norwalk Virus

The Norwalk virus is the prototype of a family of distinct groups of viruses named for places where the outbreaks occurred. Common names of the illness caused by the Norwalk and similar viruses are viral gastroenteritis, acute nonbacterial gastroenteritis, food poisoning, and food infection.

Norwalk gastroenteritis is transmitted by the fecal-oral route via contaminated water and foods. Secondary person-to-person transmission has also been documented. Water is the most common source of outbreaks and may include water from municipal supplies, wells, recreational lakes, swimming pools, and water stored aboard cruise ships. Shellfish and salad ingredients are the foods most often implicated in Norwalk virus outbreaks. Foods other than shellfish are usually contaminated by ill food handlers.

All individuals who ingest the virus and who have not recently (within 24 months) had an infection with the same or related strain, are susceptible to infection and can develop the symptoms of gastroenteritis. Disease is more frequent in adults and older children than in the very young.

The Norwalk virus is self-limiting, mild, and characterized by nausea, vomiting, diarrhea, and abdominal pain. Headache and low-grade fever may occur. Severe illness or hospitalization is very rare.

Salmonella

Salmonella is a family of bacteria that can cause diarrheal illness in humans. The elderly, infants, and those with impaired immune systems are more likely to have severe illness. Salmonellosis is more common in summer than winter. Children are the most likely to get salmonellosis.

Salmonella bacteria are usually transmitted by eating foods contaminated with animal feces. Most people infected with Salmonella develop diarrhea, fever, and abdominal cramps, and most recover without treatment. However, sometimes the diarrhea may be so severe that the patient needs to be hospitalized. Rarely, the Salmonella infection may spread from the intestines to the blood stream, and then to other body sites; it can cause serious illness or death unless the person is treated promptly with antibiotics.

Shigella

The only reservoir for Shigella organisms is humans. Infected people who fail to thoroughly clean their hands after defecation may spread infection to others directly by physical contact or indirectly by contaminating food. Water that has been contaminated with human feces can also transmit the infection. Shigellosis typically begins with fever, abdominal pain, and diarrhea. The diarrhea may become bloody after a day or more, and usually resolves in about a week. Infections without symptoms can occur.

Reducing the Risk of Foodborne Illness/Pathogen Transmission

Handwashing with soap and running water can prevent the spread from one person to another and to food. Food and water supplies should be kept safe from contamination by human feces and by sewage-contaminated water. Poultry and meat should be well-cooked. Consumers should avoid raw or unpasteurized milk or other dairy products. Produce should be thoroughly washed before being served. PMA supports the Partnership for Food Safety Education, particularly its safe produce handling messages for consumers.

Cross-contamination of foods must be avoided. Uncooked meats should be kept separate from produce, cooked foods, and ready-to-eat foods. Hands, cutting boards, counters, knives, and other utensils should be washed thoroughly after handling uncooked foods. Hands should be washed before handling any food and between handling different food items.