The top five germs that cause illnesses from food eaten in the United States are:

1.  Norovirus

Norovirus is the leading cause of gastroenteritis, or what we commonly think of as stomach flu symptoms. It causes 23 million cases of gastroenteritis per year, or over half of all gastroenteritis cases in the U.S., and is the second most common virus after the common cold.

Norovirus is usually transmitted from the feces to the mouth, either by drinking contaminated food or water or by passing from person to person. Because noroviruses are easily transmitted, are resistant to common disinfectants, and are hard to contain using normal sanitary measures, they can cause extended outbreaks.

Symptoms of Norovirus

The norovirus incubation period tends to be 24 to 48 hours, after which symptoms begin to appear. An infection normally lasts only 24 to 60 hours. However, in some cases, dehydration, malnutrition, and even death can occur. These complications are more likely among children, older people, and patients in hospitals and nursing homes with weakened immune systems. Common symptoms include:

  • Nausea
  • Diarrhea
  • Vomiting
  • Abdominal pain
  • Headache
  • Low-grade fever

Norovirus Diagnosis

Norovirus usually takes its course and goes away on its own after one to three days. It is hard to diagnose using samples in a lab, and so is usually diagnosed based on the combination of common symptoms, including mild fever, vomiting, and short duration of illness.

Norovirus Treatment

There is no specific treatment for norovirus. However, it is essential to replenish fluids and minerals, as these are depleted with diarrhea.

How to Prevent Norovirus Infection

The good news is that norovirus does not multiply on food, since it is a virus and not a bacterium. There is no way to tell whether foods – like shellfish, which are often eaten raw – are contaminated with norovirus. The only way to assure you don’t get norovirus from foods like shellfish is to cook them thoroughly. Here are other norovirus prevention methods:

  • Wash hands properly, especially after being at events with catered meals, nursing homes, schools, or on cruise ships
  • Wash raw vegetables thoroughly before serving them
  • While traveling, only drink boiled drinks or carbonated bottled beverages
  • Avoid letting anyone known to have norovirus in kitchen space

2.  Salmonella

Salmonella is the second most common intestinal infection in the United States. More than 7,000 cases of Salmonella were confirmed in 2009; however, the majority of cases go unreported. The Centers for Disease Control and Prevention estimates that over 1 million people in the U.S. contract Salmonella each year, and that an average of 20,000 hospitalizations and almost 400 deaths occur from Salmonella poisoning, according to a 2011 report.

Salmonella infection usually occurs when a person eats food contaminated with the feces of animals or humans carrying the bacteria.  Salmonella outbreaks are commonly associated with eggs, meat and poultry, but these bacteria can also contaminate other foods such as fruits and vegetables. Foods that are most likely to contain Salmonella include raw or undercooked eggs, raw milk, contaminated water, and raw or undercooked meats.

Salmonella is generally divided into two categories. Non-typhoidal Salmonella is the most common form, and is carried by both humans and animals. Most serotypes of Salmonella, such as Salmonella Javiana and Salmonella Enteritidis cause non-typhoidal Salmonella.  Typhoidal Salmonella, which causes typhoid fever, is rare, and is caused by Salmonella Typhi, which is carried only by humans.

Symptoms of Salmonella Infection

Symptoms of Salmonella infection, or Salmonellosis, range widely, and are sometimes absent altogether. The most common symptoms include diarrhea, abdominal cramps, and fever.

Typical Symptoms of Salmonella infection: Appear 6 to 72 hours after eating contaminated food and last for 3 to 7 days without treatment.

  • Diarrhea
  • Abdominal Cramps
  • Fever of 100 F to 102 F

Additional symptoms

  • Bloody diarrhea
  • Vomiting
  • Headache
  • Body Aches

Typhoid Fever Symptoms: Symptoms of typhoid fever appear between 8 and 14 days after eating contaminated food and last anywhere from 3 to 60 days. They include a fever of 104 F, weakness, lethargy, abdominal pain, coughing, nosebleeds, delirium, and enlarged organs. Typhoid fever is a serious illness that can result in death.

Complication of Salmonella

Complications of Salmonella poisoning are more likely to occur among young children and people age 65 or older. Possible complications include:

Reactive ArthritisReactive arthritis is thought to occur in 2 to 15 percent of Salmonella patients. Symptoms include inflammation of the joints, eyes, or reproductive or urinary organs. On average, symptoms appear 18 days after infection

Reactive Arthritis: Campylobacter infection may also lead to reactive arthritis. Symptoms include inflammation of the joints, eyes, or reproductive or urinary organs. On average, symptoms appear 18 days after infection

Focal Infection: A focal infection occurs when Salmonella bacteria takes root in body tissue and causes illnesses such as arthritis or endocartitis. It is caused by typhoidal Salmonella only.

Salmonella Treatment

Salmonella infections generally last 3 to 7 days, and often do not require treatment. People with severe dehydration may need rehydration through an IV.

Antibiotics are recommended for those at risk of invasive disease, including infants under three months old. Typhoid fever is treated with a 14-day course of antibiotics.

Unfortunately, treatment of Salmonella has become more difficult as it has become more resistant to antibiotics. Finding the right antibiotic for a case of Salmonella is crucial to treating this bacterial infection.

Prevention of Salmonella Infection

These safety measures can help prevent Salmonella poisoning:

  • Wash your hands before preparing food and after handling raw meats
  • Cook meat and eggs thoroughly until they reach an internal temperature of 160 F (71 C)
  • Do not eat foods containing raw eggs or milk, such as undercooked French toast
  • Avoid cooking raw meat in the microwave, as it may not reach a high enough internal temperature to kill Salmonella bacteria and may be unevenly cooked
  • Avoid bringing uncooked meat into contact with food that will not be cooked (i.e. salad)
  • Wash hands with soap after handling reptiles or animal feces
  • Always wash your hands after going to the bathroom

3.  Clostridium Perfringens

Clostridium perfringens are bacteria that produce toxins harmful to humans. Clostridium perfringens and its toxins are found everywhere in the environment, but human infection is most likely to come from eating food with Clostridium perfringens in it. Food poisoning from Clostridium perfringens fairly common, but is typically not too severe, and is often mistaken for the 24-hour flu.

Source of Clostridium Perfringens

The majority of outbreaks are associated with undercooked meats, often in large quantities of food prepared for a large group of people and left to sit out for long periods of time. Because of this, it is sometimes referred to as the “food service germ.” Meat products such as stews, casseroles, and gravy are the most common sources of illness from C. perfringens. Most outbreaks come from food whose temperature is poorly controlled. If food is kept between 70 and 140 F, it is likely to grow Clostridium perfringens bacteria.

Symptoms of Clostridium Perfringens Infection

People generally experience symptoms of Clostridium perfringens infection 6 to 24 hours after consuming the bacteria or toxins. Clostridium perfringens toxins cause abdominal pain and stomach cramps, followed by diarrhea. Nausea is also a common symptom. Fever and vomiting are not normally symptoms of poisoning by Clostridium perfringens toxins.

Illness from Clostridium Perfringens generally lasts around 24 hours, and is rarely fatal.

Complication from Clostridium Perfringens

The Type C strain of Clostridium perfringens can cause a more serious condition called Pig-bel Syndrome. This syndrome can cause death of intestinal cells and can often be fatal.

Preventing a Clostridium Perfringens Infection

To prevent infection by Clostridium perfringens, follow these tips:

  • Cook foods containing meat thoroughly
  • If keeping foods out, make sure they maintain a temperature of 140 F (60 C)
  • When storing food in the refrigerator, divide it into pieces with a thickness of three inches or less so that it cools faster
  • Reheat foods to at least 165 F (74 C)

4.  Campylobacter

Campylobacter jejuni is the most common cause of bacterial foodborne illness in the United States. Over 6,000 cases of Campylobacter infection were reported in 2009 alone, but many cases are not reported to public health authorities. A 2011 report from the CDC estimates that Campylobacter causes approximately 845,000 illnesses in the United States each year.

Campylobacter is found most often in food, particularly in chicken. Food is contaminated when it comes into contact with animal feces.  Any raw poultry may contain Campylobacter, including organic and “free range” products. In fact, studies have found Campylobacter contamination on up to 88 percent of chicken carcasses. Despite the commonness of Campylobacter, however, infections are usually isolated events, and widespread outbreaks are rare.

Campylobacter Symptoms

Symptoms of food poisoning from Campylobacter usually occur 2 to 5 days after a person eats contaminated food, but may take up to 10 days to appear. The most common symptom of a Campylobacter infection is diarrhea, which is often bloody.  Typical symptoms include:

  • Diarrhea: Diarrhea ranges from mild to severe and is often bloody
  • Fever
  • Nausea
  • Vomiting
  • Abdominal pain
  • Headache
  • Muscle pain

Two age groups are most commonly affected by Campylobacter: children under 5 years of age and young adults aged 15-29.

Complications of Campylobacter Infection

Although complications from Campylobacter food poisoning are unlikely, they do occur in some cases. The following is a list of possible long-term consequences of Campylobacter infection.

Guillan-Barré Syndrome (GBS): Although rare, Guillan-Barré Syndrome is the most common cause of acute generalized paralysis in the western world.  GBS occurs when the antibodies the body builds up against Campylobacter attack one’s nerve cells. Symptoms of GBS appear several weeks after diarrheal illness. Approximately one in every 1000 reported Campylobacter cases results in GBS.

Reactive Arthritis: Campylobacter infection may also lead to reactive arthritis. Symptoms include inflammation of the joints, eyes, or reproductive or urinary organs. On average, symptoms appear 18 days after infection.

Other complications: Campylobacter may also cause appendicitis or infect specific parts of the body, including the abdominal cavity, the heart, the central nervous system, the gall bladder, the urinary tract, or the blood stream.

Diagnosis of Campylobacter Infection

To assess whether someone has a Campylobacter infection, doctors take a stool sample and send it to a laboratory for testing.  However, if the stool sample is taken after an individual has begun antibiotic treatment, the test results may be falsely negative.

Campylobacter Treatment

Campylobacter infections usually resolve after about a week, although treatment with antibiotics can shorten the course of the illness. Patients with Campylobacter poisoning should drink lots of fluids to stay hydrated as long as the diarrhea lasts. Antidiarrheal medication may also help lessen symptoms.

The amount of foodborne bacteria resistant to antibiotics is on the rise, so certain antibiotics may prove ineffective at treating a given type of Campylobacter. Finding an effective antibiotic is key to treating this bacterial infection.

How to Prevent Campylobacter Infection

Campylobacter jejuni grows easily if contaminated foods are left out at room temperature. The bacterium is sensitive to heat and other sterilization methods, including pasteurization, cooking meat fully, and water chlorination. Follow these easy safety procedures to avoid Campylobacter infection.

  • Make sure the thickest part of any poultry product you are cooking reaches 165 F (74 C)
  • Choose the coolest part of the car to transport meat and poultry home from the store
  • Defrost meat and poultry in the refrigerator or microwave, making sure juices do not drip
  • Do not cook stuffing inside the bird
  • Never leave food out at room temperature for over two hours
  • Use pasteurized milk and eggs
  • Wash fruits and vegetables carefully
  • Wash hands thoroughly after…
  • Contact with pets or farm animals
  • Preparing food, especially poultry
  • Changing diapers
  • Children return from school or daycare

Note: Helicobacter pylori, a bacterium that causes peptic ulcers and gastritis, is often misconstrued as a Campylobacter. While it was originally thought that Helicobacter pylori was indeed a Campylobacter due to its similar structure, it is now known to be a different bacteria.

5.  Staphylococcus aureus

Staphylococcus aureus (S. aureus), often referred to as “staph,” is a bacterium commonly carried on the skin or in the nose of healthy people. S. aureus typically causes a skin infection, but can cause infections in the bloodstream and major organs. Methicillin-resistant S. aureus (MRSA) occurs when the bacteria become resistant to the antibiotic, methicillin and other more common antibiotics such as oxacillin, penicillin and amoxicillin, making it more difficult to treat. The rate of invasive MRSA (infections in typically sterile sites like the bloodstream) is estimated to be 32 per 100,000 persons in the United States; the mortality (death) rate is thought to be about 6 per 100,000 persons. The risk of invasive MRSA infections is highest among older individuals, Blacks/African Americans, and men.

MRSA infections were initially limited to hospitals and nursing homes, especially among patients with weakened immune systems. Since the 1980s, community-acquired cases and outbreaks also have been reported. Community acquired cases are those not related to past year hospitalization or medical procedures like dialysis, surgery, or catheterization. These infections typically occur among otherwise healthy individuals and are more likely to be limited to skin infections. An increase in the virulence of MRSA bacteria in the past decade, however, has been responsible for more severe and sometimes fatal community acquired infections. More recently, MRSA has been identified in food animals and a few outbreaks have been ‘food-initiated’ or foodborne. In one such outbreak, those affected developed typical foodborne illness symptoms, such as vomiting and stomach cramps,

Sources and Transmission

The major site where people carry S. aureus is in the nasal passages. Approximately 25% to 30% of the population is colonized (when bacteria are present, but not causing an infection) with S. aureus, but only about 1% of the population is colonized with MRSA. The main mode of transmission of staph and MRSA is through hands, which may become contaminated by contact with colonized or infected individuals or through contact with colonized or infected body sites of other persons. Contact with devices, items, or environmental surfaces contaminated with body fluids containing staph or MRSA may also cause infection. Other factors contributing to transmission include close skin-to-skin contact, crowded conditions, and poor hygiene.

Studies in recent years have demonstrated that food-producing animals also carry MRSA. Studies conducted in the U.S. as well as several other countries, including Austria, Canada, China, Belgium, Denmark, France, Italy, South Korea, Taiwan, and The Netherlands, have isolated MRSA mainly from pigs. Other animals testing positive for MRSA have included chickens, cattle, and dairy cows. In addition, the testing of raw meat samples from slaughter houses and retail markets has revealed MRSA in several countries. This is likely due to the high use of antibiotics in food animal production. Estimates of the amounts of growth-promoting antibiotics used in U.S. animal production range from 3.1 million to approximately 25 million pounds annually. In some instances, animal strains are similar or identical to human strains. In fact, the presence of MRSA in food-producing animals has also led to the transmission of MRSA to farmers, their families, and veterinarians, resulting in human colonization.

Of even greater concern is the identification of MRSA in retail meats and food products, including pork, beef, and dairy products. This has occurred in the U. S. as well as in Austria, China, The Netherlands, Portugal, and South Korea. However, few foodborne or food-initiated outbreaks have been reported. One ‘food-initiated’ outbreak in The Netherlands involved the transmission of MRSA from a colonized but healthy hospital dietary worker to a patient through food. The contaminated food (which tested positive for MRSA) was ingested by the patient who was severely immunocompromised, and the patient contracted a fatal infection. Transmission from that patient to other hospital workers and subsequently to other patients resulted in a major outbreak. In another food-related case, a community-acquired foodborne illness outbreak occurred in Tennessee. In that outbreak, a family developed typical foodborne illness symptoms after eating food prepared by a commercial foodhandler who was colonized with MRSA (see details below)


Community-acquired MRSA infections most often present as a skin or soft tissue infection such as a boil or abscess. Individuals frequently recall a “spider bite”. The involved site is red, swollen, and painful and may have pus or other drainage. MRSA infections also can cause more serious infections, such as necrotizing fasciitis, a rapidly progressive, life-threatening infection that involves skin, soft tissue, and deep fascia; bloodstream infections; or pneumonia, leading to symptoms of shortness of breath, fever, and chills. As seen in at least one outbreak, individuals with foodborne illness caused by MRSA may experience nausea, vomiting and stomach cramps.

According to the Centers for Disease Control and Prevention (CDC), individuals with MRSA infections that meet all of the following criteria likely have community-acquired MRSA infections:

  • Diagnosis was made in the outpatient setting or by a culture positive for MRSA within 48 hours after admission to the hospital.
  • No medical history of MRSA infection or colonization.
  • No medical history in the past year of:
    a. Hospitalization
    b. Admission to a nursing home, skilled nursing facility, or hospice
    c. Dialysis
    d. Surgery

Detection and Treatment

In general, a culture is obtained from the infection site (skin, blood, or urine) and sent to the microbiology laboratory. In the case of a skin Infection, a culture is taken from a small biopsy of skin or drainage from the infected site. A sputum culture should be taken in the event of pneumonia. If S. aureus is isolated, the organism should be tested to determine which antibiotics will be effective for treating the infection.

Staph skin infections, such as boils or abscesses, may be treated by incision and drainage, depending on severity. Antibiotic treatment, if indicated, should be guided by laboratory testing of the bacteria to determine antibiotic susceptibility.


Frequent handwashing is the most important way to prevent spread of staph in the community. If an individual has a skin infection, it should be kept covered. Keep wounds that are draining or have pus covered with clean, dry bandages until healed. Bandages and tape can be discarded with the regular trash.

Family members and others in close contact should wash their hands frequently with soap and water or use an alcohol-based hand sanitizer, especially after changing the bandage or touching the infected wound. Do not share personal items, such as towels, washcloths, razors, clothing or uniforms, that may have had contact with the infected wound or bandage. Wash sheets, towels, and clothes that become soiled with water and laundry detergent. Use a dryer to dry clothes completely.

Since little is known about the transmission of MRSA through food, other than through foodhandlers, there are no specific recommendations about the prevention of foodborne illness with regard to MRSA. In general, individuals should wash their hands with soap and water before preparing food, especially commercial foodhandlers; wash produce; wash cutting boards often; wash hands, utensils, and cutting boards after they have been in contact with raw meat or poultry and before they touch another food; and refrigerate food within 2 hours of serving. Use a food thermometer to cook meat and poultry to proper temperatures and keep hot foods hot; cold foods should be kept at 40°F or below.