Spinach Now Safe to Eat, But Issues Linger

An estimated 76 million cases of food-borne disease occur each year in the United States, causing about 325,000 hospitalizations and 5,000 deaths, according to the Centers for Disease Control and Prevention (CDC). The majority of these are caused by caused by Campylobacter, Salmonella, and E. coli O157:H7 bacteria, and by a group of viruses called calicivirus (also known as the Norwalk and Norwalk-like viruses.)

Of the 76 million cases, approximately 73,000 can be attributed to E. coli O157:H7. Hundreds of harmless strains of E. coli (Escherichia coli) can be found in nature, particularly in the intestinal tracts and feces of humans and other warm-blooded animals, but certain strains of the bacteria - such as O157:H7 - can cause severe illness and, rarely, death.

"E. coli infections might seem more common than they actually are," says Rick Gillis, MD, a Medical College of Wisconsin Assistant Professor of Medicine who practices at the Sargeant Internal Medicine Clinic.

"People become aware of E. coli, especially O157:H7, because they hear about it on the news when an outbreak occurs," Dr. Gillis notes. "There are many, many infections that people get from food and water, but most are mild and don't cause serious symptoms. We actually see many more cases of Campylobacter infection, usually caused by contact with raw poultry." Campylobacter cases are usually individual, rarely occurring in outbreaks.

Current Outbreak
The recent E. coli O157:H7 outbreak was caused by fresh spinach and spinach-containing products from brands processed by a California company called Natural Selection Foods. (Some were sold under the Dole brand name). The implicated products had a "use by" date of October 1, 2006 or earlier. Frozen and canned spinach were not involved.

As of October 6, 2006, about 200 cases of people infected with the specific outbreak strain of E. coli O157:H7 were reported to the CDC from 26 states; 3 of these people died. Forty-nine of the cases, and one death, occurred in Wisconsin. The two other confirmed deaths occurred in Idaho and Nebraska. These numbers include only cases that have been reported to and confirmed by the CDC; it is likely that that more people fell ill with less severe symptoms or their cases were not confirmed by the CDC

Among the people who were confirmed with E. coli O157:H7, 102 (51%) were hospitalized and 31 (16%) developed a type of kidney failure called hemolytic-uremic syndrome (HUS). Eighty percent of the people who knew when their illness began said they became ill between August 19 and September 5.

The FDA has announced that spinach is now safe to eat.

How E. Coli Infections Spread
Outbreaks of E. coli O157:H7 infection occur regularly in the US. "When we first started hearing about E. coli O157:H7 infections, they were almost always traced back to contaminated ground beef," Dr. Gillis says. Although this remains the leading cause, the illness has also been traced to unpasteurized fruit juices, leafy vegetables, bean sprouts, and contaminated drinking water.

E. coli O157:H7 can also be spread person-to-person, especially among children in day care centers. In addition, infection can occur after drinking raw milk, swimming in or drinking sewage-contaminated water, or having direct contact with an infected person.

Bacteria in loose stool of infected persons can be passed from one person to another if hygiene habits are inadequate; this is common among toddlers who are not toilet trained. Family members and playmates of these children are at high risk of becoming infected.

Hand washing before and after eating or using the toilet is extremely important in households where someone has an E. coli O157:H7 infection. The organism can still be present in the bowel movements of young children for a week or two after their illness ends, so they can continue to spread the disease even when they are no longer sick.

To prevent transmission to those who are most at risk for serious complications, infected individuals should avoid direct contact with infants, toddlers, immunocompromised individuals, and the elderly.

Anyone with a diarrheal illness should avoid swimming in public pools or lakes, sharing baths with others, or preparing food for others.

Symptoms
E. coli O157:H7 infection often causes severe bloody diarrhea and abdominal cramps. Symptoms usually begin from 2 to 5 days after ingesting contaminated foods or liquids, and can last for 5 to 10 days. E. coli O157:H7 toxins can damage the lining of the intestines and cause other symptoms such as nausea, fatigue, or vomiting. Although low-grade fever might be present, more typically there is no fever.

In fact, says Dr. Gillis, "even before lab tests have been completed, this is one of the initial ways we might suspect an infection is more likely to be E. coli O157:H7 rather than Campylobacter. People who are ill with Campylobacter tend to have fevers that start prior to the diarrheal stage of the illness, while those infected with O157:H7 generally have no fever or a very mild one." Stool samples are tested for all typical food-borne pathogens.

Although most healthy adults recover from E. coli O157:H7 completely within a week, some develop a form of kidney failure called hemolytic uremic syndrome (HUS). A small proportion of persons with hemolytic uremic syndrome (HUS) have immediate complications with lifelong implications such as blindness, paralysis, persistent kidney failure, and the effects of having part of their bowel removed. Many persons with hemolytic uremic syndrome have mild abnormalities in kidney function many years later. HUS is most likely to occur in young children.

Diagnosis
Like most diarrheal diseases, infection with E. coli O157:H7 is confirmed by a lab test that detects the bacterium in stool. Anyone who suddenly has diarrhea with blood should have their stool tested for E. coli O157:H7.

Treatment
Most people recover from E. coli O157:H7 infection without specific treatment. Antibiotics should not be used to treat this infection; in fact treatment with some antibiotics could even lead to kidney complications. Anti-diarrheal agents such as loperamide (e.g., Imodium) should also be avoided.

Those who become severely ill with hemolytic uremic syndrome are treated in an intensive care unit; blood transfusions and kidney dialysis are often required. With intensive care, the death rate for hemolytic uremic syndrome is 3% to 5%.

Preventing Food-Borne Illness in the Home
Even if food has been contaminated, there are still techniques that will greatly reduce the chances of becoming infected with E. Coli bacteria, says Dr. Gillis. "The most important actions that people can take are to wash their hands frequently or use sanitizing gels (these are especially useful when soap and water aren't available), wash foods thoroughly, and cook meats completely."

Food Preparation

• Wash hands, utensils, and surfaces with hot, soapy water before, during, and after handling food.
• Wash hands thoroughly after going to the bathroom or changing diapers (again, sanitizing gels can be substituted if necessary). Make sure that people with diarrhea, especially children, wash carefully with soap after bowel movements. Anyone with a diarrheal illness should avoid food preparation.
• Eat only thoroughly cooked ground beef. Cook ground beef products to an internal temperature of 160 degrees Fahrenheit. People who cook ground beef without using a thermometer can decrease their risk of illness by not eating ground beef patties that are still pink in the middle.
• Don't cross-contaminate food. Keep unwashed or raw food separate from food that is ready to eat, and use separate plates and utensils for raw foods and ready foods. At the grocery store, separate raw meat, poultry, seafood, and eggs from other in grocery bags.
• Wash fresh fruits and vegetables thoroughly before eating. Bacteria are sticky, so even thorough washing might not remove all contamination. Remove the outer leaves of leafy vegetables.
• People at high risk of complications from food-borne illness, particularly children under 5 years of age, immunocompromised persons, and the elderly, might have to choose cooked vegetables and peeled fruits.
• Avoid unpasteurized milk and juices. Commercial juice with an extended shelf-life that is sold at room temperature (e.g. juice in cardboard boxes, vacuum sealed juice in glass containers) has been pasteurized. Juice concentrates are also heated sufficiently to kill pathogens.

Cleaning

• Wash countertops with a solution of 5 milliliters (1 teaspoon) of chlorine bleach in about 1 liter (1 quart) of water or with a commercial kitchen cleaning agent.
• Dish cloths and sponges can harbor bacteria and promote their growth. Put them in the microwave for one minute between uses and wash them weekly in hot water in the washing machine.
• Periodically sanitize kitchen sink drains by pouring a solution of 5 milliliters (1 teaspoon) of bleach to 1 liter (1 quart) of water or a commercial kitchen cleaning agent down the sink drain. Food particles often get trapped in drains and disposals and, along with moistness, create an ideal environment for bacteria growth.
• Keep the refrigerator clean. Wipe us spills immediately and clean surfaces with a solution of 5 milliliters (1 teaspoon) of chlorine bleach in about 1 liter (1 quart) of water, with a commercial kitchen cleaning agent, or with hot, soapy water, and then rinsed. Once a week, throw out perishable foods that are past their expiration date.

History/Future
Cattle are the principal source of E. coli. Because the organism lives in the intestines of healthy cattle, preventive measures on cattle farms, during meat processing, and during the growth, harvest and processing of produce are being investigated. (Occasionally, the infection is transmitted by contact with infected animals.)

Changes in the preparation of animals for slaughter and in slaughter and processing methods could decrease the contamination of carcasses with E. coli and the subsequent contamination of meat. Since 2002, many meat producers began testing ground beef for E. coli and withholding it from the market until the test is negative.

Cattle manure is an important source of E. coli infection. Manure can contaminate the environment, including streams that flow through produce fields and are used for irrigation, pesticide application, or washing.

There has been a long history of E. coli O157:H7 outbreaks involving leafy greens from the central California region. The Food and Drug Administration (FDA) and the State of California expect the industry to develop a comprehensive plan designed to minimize the risk of another outbreak due to E. coli O157:H7 in spinach grown all leafy greens in central California.

Recently, public health, agriculture, and environmental officials have expressed growing concern about keeping the nation's food and water supply safe from terrorist acts of introducing food-borne microbes. A number of US agencies, including the National Institutes of Health, CDC, Food and Drug Administration, US Department of Agriculture, and US Environmental Protection Agency, are studying this bioterrorism threat.

This article includes information from the Centers for Disease Control and Prevention, the US Food and Drug Administration, and the National Institute of Allergy and Infectious Diseases.

For further information on this topic, see the HealthLink articles How to Stop Food-Borne Illness Before it Starts, Good Food - and Why It Can Make Us Sick, and What You Can Do to Prevent Communicable Diseases.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.