In the United States alone, an estimated 73,000 cases of E. coli O157:H7 occur each year. Approximately 2,000 people are hospitalized and 60 die from E. coli infections or complications from an E. coli infection.

While E. coli bacteria are mostly associated with foodborne illness, E. coli O157:H7 cases actually account for less than 1 percent of all foodborne illnesses, according to the Centers for Disease Control and Prevention.

Strains

There are multiple strains of Escherichia coli bacteria, most of which are harmless. E. coli O157:H7 is the strain most often linked to foodborne outbreaks and infections. Harmful E. coli strains, such as O157:H7, produce a toxin called Shiga toxin, which is responsible for causing diseases. The bacteria that produce the Shiga toxins are called “Shiga toxin-producing” E. coli, or STEC.

Other E. coli strains are often called “non-O157H7 STEC” and are less likely to cause illness in people. However, some of the non-O157:H7 STEC strains can still produce severe manifestations of STEC illness. Serogroups that most often cause illness in the United States are: O26, O111 and O103.

Source

One strain or another of E. coli bacteria are everywhere in the environment, so there is potential for bacteria ingestion with everything we eat, drink or touch

E. coli O157:H7 is thought to live primarily in the intestines of cattle, although it has also been found in intestines of other ruminant animals, including chickens, deer, sheep and goats. Pigs and birds can also contract E. coli from the environment and spread it to humans. Animals that carry STEC, which causes human illness, generally do not show symptoms of an infection themselves.

Humans also carry non-O157:H7 STEC strains of E. coli naturally in their intestines.  E. coli bacteria are  the most frequent cause of urinary tract infections and can also cause infections in wounds. E. coli can also be beneficial, as it aids the body in natural digestive processes.

People are often exposed to E. coli O157:H7 by consuming:

• Ground beef
• Unpasteurized apple cider, orange juice or milk
• Alfalfa sprouts
• Contaminated water

E. coli outbreaks can also be transmitted from person-to-person through oral contact with infected fecal matter, often in highly-probable contamination settings such as daycares, hospitals and nursing homes.

E. coli is also the primary bacterial cause of travelers’ diarrhea which is the most common illness affecting travelers—approximately 20 to 50 percent. Eating food or water contaminated with E. coli can cause symptoms including watery diarrhea and possibly cramps or a low-grade fever.  

Incubation

E. coli can survive outside the intestines in feces and contaminate almost anything in the environment.

The “incubation period” refers to the period from when the STEC bacteria are ingested to the point  a person starts feeling ill. The incubation period is usually 3-4 days, although it may be as short as one day or long as 10 days. 

By the time a person gets rid of an E. coli infection, STEC has typically disappeared from the feces. However, they could be present in the intestines for several weeks or even months. Adults tend to rid their bodies of STEC faster than young children.

Symptoms

Initial symptoms of STEC include mild stomach pain or non-bloody diarrhea that worsens over several days.  While symptoms vary from person-to-person, they often progress to include severe stomach cramps, bloody diarrhea and vomiting. Fevers are usually less than 101 degrees Fahrenheit, or 38.5 degrees Celsius, if they are present.

Most people recover from mild STEC within 5-7 days, although it is possible to contract more severe, life threatening strains. Young children and the elderly are most likely to develop a more severe illness from STEC.

In children, E. coli is the main cause of Hemolytic Uremic Syndrome, a condition that can cause life-threatening kidney failure. Around 5 to 10 percent of STEC diagnosed people develop HUS. HUS symptoms include decreased urination frequency, sleepiness and paleness in cheeks and inside the lower eyelids. People infected with HUS need immediate hospitalization to prevent permanent kidney damage and death.

Action

Hydration is the most important therapy for mild to severe STEC infections. Antibiotics and anti-diarrheal agents are not used to treat the infection as they may increase the risk of HUS.

Stool sample testing is used to detect and confirm an E. coli infection. Most individuals recover from an infection within two weeks of supportive care, with close attention to hydration and nutrition.

Doctors visits or hospitalization is necessary if symptoms worsen to bloody diarrhea or frequent vomiting.

Prevention

Eating correctly prepared ground beef, avoiding raw and unpasteurized dairy products and juices and avoiding cross-contamination are the most important factors in preventing E. coli.

Follow these guidelines to ensure that you and your family don't become infected:

Keep raw meat separate from ready-to-eat foods and never place cooked hamburgers on plates that held raw meat to avoid cross-contamination. Also be aware of cross-contamination through utensils, counters and cutting boards. Cook ground beef thoroughly to an internal temperature of at least 160 degrees Fahrenheit, or 70 degrees Celsius. A meat thermometer is the only way to confirm bacteria were killed off.

Avoid raw, unpasteurized dairy products, juice or cider. Although not always marked on the label, beverages sold at room-temperature have been pasteurized, or heated to a temperature high enough to kill pathogens.  Unpasteurized milk is illegal to sell in most states, although it is still accessible through milking one’s own cow or through some pet food lines. Unpasteurized milk should always be avoided and has been linked to foodborne illness.  Some Mexican and soft cheeses are also unpasteurized.

Wash fruits and vegetables thoroughly as they can sometimes become contaminated from water runoff in fields or through direct contact with animal feces. Cook vegetables that are commonly associated with E. coli, such as alfalfa sprouts, or do not feed them to children with under-developed immune systems. 

Only drink water that has been treated, including sterilized bottled water. Tap water is usually OK to drink and is under strict regulation by the Environment Protection Agency.

Avoid swallowing water in lakes, pools, ponds, streams and backyard “kiddie” pools, as they can sometimes contain E. coli bacteria.

Wash hands thoroughly after using the bathroom, changing diapers, visiting petting zoos, hospitals, care homes and even your own backyard. Hand-washing prevents accidentally contracting the bacteria orally.

Sources:

Centers for Disease Control and Prevention. “Escherichia coli,” http://www.cdc.gov/nczved/dfbmd/disease_listing/stec_gi.html#16; accessed 14 Oct. 2009

Marler Clark LLP. “E.coli Blog,” http://www.ecoliblog.com/promo/about/; accessed 14 Oct. 2009.

Web Md. “E.coli Infection,” http://www.webmd.com/a-to-z-guides/e-coli-infection-symptoms; accessed 14 Oct. 2009.

Mayo Clinic. “Hemolytic uremic syndrome,” http://www.mayoclinic.com/health/hemolytic-uremic-syndrome/DS00876 ; accessed 14 Oct. 2009.