The CDC estimates that 76 million foodborne illness, or food poisoning, cases occur in the United States every year, which means that one in four Americans contracts a foodborne illness annually after eating foods contaminated with such pathogens as E. coli O157:H7, Salmonella, Hepatitis A, Campylobacter, Shigella, Norovirus, and Listeria. Approximately 325,000 people are hospitalized with a diagnosis of food poisoning, and 5,000 die. The estimated costs in terms of medical expenses and lost wages or productivity are between $6.5 and $34.9 billion (Buzby and Roberts, 1997; Mead, et al., 1999).
While most foodborne illness cases go unreported to health departments, nearly 13.8 million food poisoning cases are caused by known agents — 30% by bacteria, 67% by viruses, and 3% parasites (Mead, et al., 1999).
A recent report (2005) released by the CDC in collaboration with the FDA and USDA showed important declines in foodborne infections due to common bacterial pathogens in 2004. From 1996-2004, the incidence of E. coli O157:H7 infections decreased 42 percent. Campylobacter infections decreased 31 percent, Cryptosporidium dropped 40 percent, and Yersinia decreased 45 percent. Salmonella infections dropped 8 percent, but only one of the five most common strains declined significantly. The incidence of Shigella, which is found in a wide variety of foods, did not change significantly from 1996 through 2004. Vibrio infections increased 47 percent.
Foodborneillness.com describes seven of the most commonly recognized bacteria and viruses that cause food poisoning. In addition to a general description of each pathogen, we have provided information on the symptoms and risks of each kind of foodborne illness, as well as how they are detected as the cause of infection, and measures you can take to prevent contracting each type of bacterial or viral food poisoning.
Campylobacter is most common cause of bacterial foodborne illness in the United States. Over 3,000 cases were reported to the Centers for Disease Control and Prevention in 2003, or 12.6 cases for each 100,000 persons in the population. Many more cases go undiagnosed and unreported, with estimates as high as 2 to 4 million cases per year.
Poultry is the most common food implicated. Other foods include unpasteurized milk, undercooked meats, mushrooms, ground beef, cheese, pork, shellfish, and eggs. Most cases of Campylobacter infection occur as isolated, sporadic events, not as part of large outbreaks.
Other sources of Campylobacter that have been reported include children prior to toilet-training, especially in child care settings, and intimate contact with other infected individuals. C. jejuni is commonly present in the gastrointestinal tract of healthy cattle, pigs, chickens, turkeys, ducks, and geese, and direct animal exposure can lead to infection. Pets that may carry Campylobacter include birds, cats, dogs, hamsters, and turtles. The organism is also occasionally isolated from streams, lakes and ponds.
Symptoms of a Campylobacter infection
The incubation period for Campylobacteriosis (the time between exposure to the bacteria and onset of the first symptom) is typically two to five days, but onset may occur in as few as two days or as long as 10 days after ingestion of the bacteria. The illness usually lasts no more than one week but severe cases may persist for up to three weeks, and about 25% of individuals experience relapses of symptoms.
Diarrhea is the most consistent and prominent manifestation of Campylobacter infection and is often bloody. Typical symptoms also include fever, nausea, vomiting, abdominal pain, headache, and muscle pain. A majority of cases are mild, do not require hospitalization, and are self-limited. However, Campylobacter jejuni infection can be severe and life-threatening. It may cause appendicitis or infect other organs as well as the blood stream. It is estimated that about one in 1,000 cases of Campylobacter infection results in death. Death is more common when other diseases (for example, cancer, liver disease, and immune deficiency diseases) are present.
Diagnosis of a Campylobacter infection
Health care providers can look for bacterial causes of diarrhea by asking a laboratory to culture a stool sample from an ill person. Campylobacter is usually a self-limited illness; the affected person should drink plenty of fluids as long as the diarrhea lasts in order to maintain hydration. Antidiarrheal medications such as loperamide may allay some symptoms. Specific treatment with antibiotics is sometimes indicated, particularly in severe cases, and may shorten the course of the illness. Macrolide antibiotics (erythromycin, clarithromycin, or azithromycin) are the most effective agents. Fluoroquinolone antibiotics (ciprofloxacin, levofloxacin, gatifloxacin, or moxifloxacin) can also be used, but resistance to this class of drugs has been rising, at least in part due to their use in poultry feed. Consultation with a health care provider is recommended prior to taking anti-diarrheal medications or antibiotics.
Complications of a Campylobacter infection
Long-term consequences and complications can sometimes result from a Campylobacter infection. Some people may develop a rare disease that affects the nerves of the body following infection. This disease is called Guillain-Barr� syndrome (GBS). It begins several weeks after the diarrheal illness, may last for weeks to months, and often requires intensive care. Full recovery is common but some affected individuals may be left with mild to severe neurological damage. Two therapies, intravenous immunoglobulin infusions and plasma exchange, may improve the rate of recovery in patients with GBS.
Miller Fisher Syndrome (MFS) is a related neurological syndrome that can occur with a Campylobacter infection. In MFS, the nerves of the head are affected more than the nerves of the body. Another chronic condition that may be associated with Campylobacter infection is a form of reactive arthritis called Reiter’s syndrome (RS). RS typically affects large weight-bearing joints such as the knees and the lower back. It is a complication that is strongly associated with a particular genetic make-up; persons who have the human lymphocyte antigen B27 (HLA-B27) are most susceptible.
Preventing a Campylobacter infection
The single most important and reliable step to preventing Campylobacter infection is to adequately cook all poultry products. Make sure that the thickest part of the bird (the center of the breast) reaches 180 degrees F or higher. It is recommended that the temperature reaches at least 165 degrees F for stuffing and 170 degrees F for ground poultry products, and that thighs and wings be cooked until juices run clear. Do not cook stuffing inside the bird.
Transport meat and poultry home from the market in the coolest part of the vehicle (generally the trunk in winter and cab in summer). Defrost meat and poultry in the refrigerator. Place the item on a low shelf, on a wide pan, lined with paper towel; ensure that drippings do not land on foods below. If there is not enough time to defrost in the refrigerator, use the microwave.
Rapidly cool leftovers. Never leave food out at room temperature (either during preparation or after cooking) for more than 2 hours.
Avoid raw milk products.
Wash fruits and vegetables carefully, particularly if they are eaten raw. If possible, vegetables and fruits should be peeled.
Wash hands thoroughly using soap and water, concentrate on fingertips and nail creases, and dry completely with a disposable paper towel after contact with pets, especially puppies, or farm animals; before and after preparing food, especially poultry; and after changing diapers or having contact with an individual with an intestinal infection. Children should wash their hands on arrival home from school or daycare.
Cyclospora is a parasite composed of one cell, too small to be seen without a microscope. The organism was previously thought to be a blue-green alga or a large form of Cryptosporidium. Cyclospora cayetanensis is the only species of this organism found in humans. The first known human cases of illness caused by Cyclospora infection (that is, cyclosporiasis) were first discovered in 1977. An increase in the number of cases being reported began in the mid-1980s, in part due to the availability of better diagnostic techniques. Over 15,000 cases are estimated to occur each year in the United States. The first outbreak in North America occurred in 1990 from contaminated water. Since then, several outbreaks of cyclosporiasis have been reported in the U.S. and Canada, many associated with eating fresh fruits or vegetables. In some developing countries, cyclosporiasis is common among the population and travelers to those areas have become infected as well.
Where does Cyclospora come from?
Cyclospora is spread by people ingesting water or food contaminated with infected stool. For example, exposure to contaminated water among farm workers may have been the original source in raspberry-associated outbreaks in North America.
Cyclospora needs time (one to several weeks) after being passed in a bowel movement to become infectious. Therefore, it is unlikely that Cyclospora is passed directly from one person to another. It is not known whether or not animals can be infected and pass infection to people.
What are the typical symptoms of a Cyclospora infection?
Cyclospora infects the small intestine (bowel) and usually causes watery diarrhea, bloating, increased gas, stomach cramps, loss of appetite, nausea, low-grade fever, and fatigue. In some cases, vomiting, explosive diarrhea, muscle aches, and substantial weight loss can occur. Some people who are infected with Cyclospora do not have any symptoms. The time between becoming infected and becoming ill is usually about one week. If not treated, the illness may last from a few days up to six weeks. Symptoms also may recur one or more times (relapse). In addition, people who have previously been infected with Cyclospora can become infected again.
What are the serious and long-term risks of a Cyclospora infection?
Cyclospora has been associated with a variety of chronic complications such as Guillain-Barr� syndrome, reactive arthritis or Reiter’s syndrome, biliary disease, and acalculous cholecystitis. Since Cyclospora infections tend to respond to the appropriate treatment, complications are more likely to occur in individuals who are not treated or not treated promptly. Extraintestinal infection also appears to occur more commonly in individuals with a compromised immune system.
How is a Cyclospora infection detected?
Your health care provider will ask you to submit stool specimens to see if you are infected. Because testing for Cyclospora infection can be difficult, you may be asked to submit several stool specimens over several days. Identification of this parasite in stool requires special laboratory tests that are not routinely done. Therefore, your health care provider should specifically request testing for Cyclospora if it is suspected. Your health care provider might have your stool checked for other organisms that can cause similar symptoms.
How is a Cyclospora infection treated?
The recommended treatment for infection with Cyclospora is a combination of two antibiotics, trimethoprim-sulfamethoxazole, also known as Bactrim, Septra, or Cotrim. People who have diarrhea should rest and drink plenty of fluids. No alternative drugs have been identified yet for people with Cyclospora infection who are unable to take sulfa drugs. Some experimental studies, however, have suggested that ciprofloxacin or nitazoxanide may be effective, although to a lesser degree than trimethoprim-sulfamethoxazole. See your health care provider to discuss alternative treatment options.
How can a Cyclospora infection be prevented?
Avoiding water or food that may be contaminated is advisable when traveling. Drinking bottled or boiled water and avoiding fresh ready-to-eat produce should help to reduce the risk of infection in regions with high rates of infection. Improving sanitary conditions in developing regions with poor environmental and economic conditions is likely to help to reduce exposure.
Washing fresh fruits and vegetables at home may help to remove some of the organisms, but Cyclospora may remain on produce even after washing.
E. coli O157:H7
E. coli O157:H7 was identified for the first time at the CDC in 1975, but it was not until seven years later, in 1982, that E. coli O157:H7 was conclusively determined to be a cause of enteric disease. Following outbreaks of foodborne illness that involved several cases of bloody diarrhea, E. coli O157:H7 was firmly associated with hemorrhagic colitis.
The Centers for Disease Control and Prevention (CDC) estimated in 1999 that 73,000 cases of E. coli O157:H7 occur each year in the United States. Approximately 2,000 people are hospitalized, and 60 people die as a direct result of E. coli O157:H7 infections and complications. The majority of infections are thought to be foodborne-related, although E. coli O157:H7 accounts for less than 1% of all foodborne illness.
E. coli O157:H7 bacteria are believed to mostly live in the intestines of cattle but have also been found in the intestines of chickens, deer, sheep, goats, and pigs. E. coli O157:H7 does not make the animals that carry it ill; the animals are merely the reservoir for the bacteria.
While the majority of foodborne illness outbreaks associated with E. coli O157:H7 have involved ground beef, such outbreaks have also involved unpasteurized apple and orange juice, unpasteurized milk, alfalfa sprouts, and water. An outbreak can also be caused by person-to-person transmission of the bacteria in homes and in settings like daycare centers, hospitals, and nursing homes.
Symptoms of an E. coli O157:H7 infection
E. coli O157:H7 infection is characterized by the sudden onset of abdominal pain and severe cramps, followed within 24 hours by diarrhea. As the disease progresses, the diarrhea become watery and then may become grossly bloody – bloody to naked eye. Vomiting can also occur, but there is usually no fever. The incubation period for the disease (the period from ingestion of the bacteria to the start of symptoms) is typically 3 to 9 days, although shorter and longer periods are not that unusual. An incubation period of less than 24 hours would be unusual, however. In most infected individuals, the intestinal illness lasts about a week and resolves without any long-term problems.
Hemolytic Uremic Syndrome (HUS) is a severe, life-threatening complication of an E. coli O157:H7 bacterial infection. Although most people recover from an E. coli O157:H7 infection, about 5-10% of infected individuals goes on to develop HUS. E. coli O157:H7 is responsible for over 90% of the cases of HUS that develop in North America. Some organs appear more susceptible than others to the damage caused by these toxins, possibly due to the presence of increased numbers of toxin-receptors. These organs include the kidney, pancreas, and brain. Visit the Marler Clark sponsored Web site about Hemolytic Uremic Syndrome for more information.
Thrombotic Thrombocytopenic Purpura (TTP) is a clinical syndrome defined by the presence of thrombocytopenia (low blood platelet counts) and microangiopathic hemolytic anemia. This has generally been recognized as ‘adult HUS.” There are many possible causes, including E. coli O157:H7, all of which act through the common mechanism of inducing endothelial cell damage. The damage triggers a cascade of biochemical events that ultimately leads to the characteristic feature of TTP – widespread dissemination of hyaline thrombi, composed predominantly of platelets and fibrin, which block the terminal arterioles and capillaries (microcirculation) of most of the major body organs, commonly, the heart, brain, kidneys, pancreas and adrenals. Other organs are involved to a lesser degree. The pathophysiology of this disease results in multisystem abnormalities and the clinical manifestations of the syndrome. To learn more about Thrombotic Thrombocytopenic Purpura, visit the Marler Clark sponsored Web site about TTP.
Detection and treatment of E. coli O157:H7
Infection with E. coli O157:H7 is usually confirmed by detecting the bacteria in the stool of the infected individual. Antibiotics do not improve the illness, and some medical researchers believe that medications can increase the risk of complications. Therefore, apart from good supportive care, such as close attention to hydration and nutrition, there is no specific therapy for E. coli O157:H7 infection. The recent finding that a toxin produced by E. coli O157:H7 initially greatly speeds up blood coagulation may lead to medical therapies in the future that could forestall the most serious consequences. Most individuals recover within two weeks.
Preventing an E. coli O157: H7 infection
Eating undercooked ground beef is the most important risk factor for acquiring E. coli O157:H7. Cook all ground beef and hamburger thoroughly. Because ground beef can turn brown before disease causing bacteria are killed, use a digital instant read meat thermometer to ensure thorough cooking. Hamburgers should be cooked until a thermometer inserted into several parts of the patty, including the thickest part, reads at least 160? F. Persons 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. If you are served an undercooked hamburger or other ground beef product in a restaurant, send it back for further cooking.
Avoid spreading harmful bacteria in your kitchen. Keep raw meat separate from ready-to-eat foods. Wash hands, counters, and utensils with hot soapy water after they touch raw meat. Never place cooked hamburgers or ground beef on the unwashed plate that held raw patties. Wash meat thermometers in between tests of patties that require further cooking.
Drink only pasteurized milk, juice, or cider. Commercial juice with an extended shelf life that is sold at room temperature (such as juice in cardboard boxes or vacuum-sealed juice in glass containers) has been pasteurized, although this is generally not indicated on the label. Most juice concentrates are also heated sufficiently to kill pathogens.
Wash fruits and vegetables thoroughly, especially those that will not be cooked. Children younger than 5 years of age, immunocompromised persons, and the elderly should avoid eating alfalfa sprouts until their safety can be assured. Methods to decontaminate alfalfa seeds and sprouts are being investigated.
Drink municipal water that has been treated with chlorine or other effective disinfectants, or bottled water that has be sterilized with ozone or reverse osmosis (almost all major brands use one or the other method).
Avoid swallowing lake or pool water while swimming, especially pool water in public swimming facilities.
Avoid petting zoos and other animal exhibits unless there are good hand washing facilities available and other sanitation measures have been taken. Wash your hands and your children’s hands after handling animals.
Make sure that persons with diarrhea, especially children, wash their hands carefully with soap after bowel movements to reduce the risk of spreading infection, and that persons wash hands after changing soiled diapers. Anyone with a diarrheal illness should avoid swimming in public pools or lakes, sharing baths with others, and preparing food for others.
Hepatitis A is one of five human hepatitis viruses (hepatitis A, B, C, D, and E) that primarily infect the liver and cause illness. An estimated 80,000 cases occur each year in the U.S., although much higher estimates have been proposed based on mathematical modeling of the past incidence of infection. Each year, an estimated 100 persons die as a result of acute liver failure in the U.S. due to hepatitis A, but the rate of infection has dramatically decreased since the hepatitis A vaccine was licensed and became available in the U.S. in 1995.
Hepatitis A is a communicable (or contagious) disease that spreads from person-to-person. It is spread almost exclusively through fecal-oral contact, generally from person-to-person, or via contaminated food or water. Food contaminated with the virus is the most common vehicle transmitting hepatitis A. The food preparer or cook is the individual most often contaminating the food, although he or she is generally not ill at the time of food preparation. The peak time of infectivity, when the most virus is present in the stool of an infectious individual, is during the two weeks before illness begins. Although only a small percentage of hepatitis A infections are associated with foodborne transmission, foodborne outbreaks have been increasingly implicated as a significant source of hepatitis A infection.
Hepatitis A may also be spread by household contact among families or roommates, sexual contact, ingestion of contaminated water, ingestion of raw or undercooked fruits and vegetables or shellfish (like oysters), and from persons sharing illicit drugs. Children often have asymptomatic or unrecognized infections and can pass the virus through ordinary play to family members and other children and adults.
Symptoms of a Hepatitis A infection
Hepatitis A infection may cause no symptoms at all when it is contracted, especially in children. Such individuals will only know they were infected (and have become immune — you can only get hepatitis A once) by getting a blood test later in life. The incubation period (from exposure to onset of symptoms) is 15-50 days, with an average of 30 days. Many children and most adults will experience the sudden onset of flu-like symptoms. After a day or two of muscle aches, headache, anorexia (loss of appetite), abdominal discomfort, fever and malaise, jaundice (also termed ‘icterus”) sets in. Jaundice is a yellowing of the skin, eyes and mucous membranes that occurs because bile flows poorly through the liver and backs up into the blood. The urine will turn dark with bile and the stool will be light or clay-colored from lack of bile. When jaundice sets in, the initial symptoms begin to subside.
In general, the period of acute illness lasts from 10 days to three weeks, at which time affected individuals tend to recapture some sense of wellness. It is not unusual for blood tests to remain abnormal for six months (or more), prolonging recovery for up to a year. Most affected individuals show complete recovery within three to six months of the onset of illness. Relapse is possible, and although more common in children, it does occur with some regularity in adults.
Diagnosis and treatment of Hepatitis A
There are blood tests widely available to accurately diagnose hepatitis A; blood samples are tested for hepatitis antibodies, which are present when the immune system responds to the hepatitis virus. Antibodies of the immune globulin (Ig) M variety, which indicate acute disease, and IgG antibodies, which stay positive for life, should both be measured.
Hepatitis A infection is an acute self-limiting disease. There is no specific treatment; treatment and management is merely supportive. The liver function tests generally improve as the affected individual begins to feel better. It is therefore well-accepted that the need for rest is best determined by the person’s own perception of the severity of fatigue or malaise.
Preventing a Hepatitis A infection
Hepatitis A infection is totally preventable. Ill food-handlers should be excluded from work. Commercial food workers and other individuals who prepare food for others must always wash their hands with soap and water after using the bathroom, changing a diaper, and before preparing food. Cooking food to a temperature of 185 degrees F or higher will inactivate hepatitis A.
After a known exposure to hepatitis A, administration of a shot of immune globulin should be considered. If administered within two weeks of the exposure, it will usually be effective in preventing or at least ameliorating the disease.
Hepatitis A vaccine is the best protection from hepatitis A infection. The vaccine is recommended for persons traveling to areas with increased rates of hepatitis A, men who have sex with men, injecting and non-injecting drug users, persons with blood clotting factor disorders (such as hemophilia), persons with chronic liver disease, and children living in regions of the U.S. with increased rates of hepatitis A. The vaccine may also help protect household contacts of those with hepatitis A infection. Vaccination of food handlers would likely substantially diminish the incidence of hepatitis A outbreaks. The vaccine is licensed for individuals aged two and older, but there is good evidence that the vaccine is safe and effective at one year of age.
Listeria monocytogenes (Listeria) is a foodborne disease-causing bacteria; the disease is called listeriosis. Listeria can invade the body through a normal and intact gastrointestinal tract. Once in the body, Listeria can travel through the blood stream but the bacteria are often found inside cells. Listeria also produces toxins that damage cells. Listeria invades and grows best in the central nervous system among immune compromised persons, causing meningitis and/or encephalitis (brain infection). In pregnant women, the fetus can become infected, leading to spontaneous abortion, stillbirths, or sepsis (blood infection) in infancy.
Approximately 2,500 cases of listeriosis are estimated to occur in the U.S. each year. About 200 in every 1000 cases result in death. Certain groups of individuals are at greater risk for listeriosis, including pregnant women (and their unborn children) and immunocompromised persons. Among infants, listeriosis occurs when the infection is transmitted from the mother, either through the placenta or during the birthing process. These host factors, along with the amount of bacteria ingested and the virulence of the strain, determine the risk of disease. Human cases of listeriosis are, for the most part, sporadic and treatable. Nonetheless, Listeria remains an important threat to public health, especially among those most susceptible to this disease.
Listeria is often isolated in cattle, sheep, and fowl, and is also found in dairy products, fruits, and vegetables.
Symptoms of a Listeria infection
It is thought that ingestion of as few as 1,000 cells of Listeria bacteria can result in illness. After ingestion of food contaminated with Listeria, incubation periods (from time of exposure to onset of illness) are in the range of one to eight weeks, averaging about 31 days. Five days to three weeks after ingestion, Listeria has access to all body areas and may involve the central nervous system, heart, eyes, or other locations.
A person with listeriosis usually has fever, muscle aches, and gastrointestinal symptoms such as nausea or diarrhea. If infection spreads to the nervous system, symptoms such as headache, stiff neck, loss of balance, confusion, obtundation (decreased consciousness) or convulsions can occur. With brain involvement, listeriosis may mimic a stroke. Infected pregnant women will ordinarily experience only a mild, flu-like illness; however, infection during pregnancy can lead to miscarriage, infection of the newborn or even stillbirth. Pregnant women are about 20 times more likely than other healthy adults to get listeriosis; about one-third of listeriosis cases happen during pregnancy. The incidence of listeriosis in the newborn is 8.6 cases per 100,000 live births. The perinatal and neonatal mortality rate (stillbirths and early infant deaths) from listeriosis is 80%.
Diagnosis and treatment of a Listeria infection
If you have symptoms of listeriosis, a health care provider can have a blood or spinal fluid test done to detect the infection. During pregnancy, a blood test is the most reliable way to find out if your symptoms are due to listeriosis. If you are in a high-risk group, have eaten the contaminated product, and within 2 months become ill with fever or signs of serious illness, you should contact your health care provider and inform him or her about this exposure.
There are several antibiotics with which Listeria may be treated. When infection occurs during pregnancy, antibiotics given promptly to the pregnant woman can often prevent infection of the fetus. Babies with listeriosis receive the same antibiotics as adults, although a combination of antibiotics is often used until physicians are certain of the diagnosis.
Preventing a Listeria infection
General recommendations include: thoroughly cook raw food from animal sources; keep uncooked meats separate from vegetables and from cooked and ready-to-eat foods; avoid unpasteurized (raw) milk or foods made from unpasteurized milk; wash hands, knives, and cutting boards after handling uncooked foods; wash raw vegetables thoroughly before eating; and consume perishable and ready-to-eat foods as soon as possible.
Recommendations for persons at high risk , such as pregnant women and persons with weakened immune systems, in addition to the recommendations listed above, include: do not eat hot dogs, luncheon or deli meats, unless they are reheated until steaming hot, and wash hands after handling those products; do not eat soft cheeses (such as feta, Brie, Camembert, blue-veined, or Mexican-style cheese), unless they have labels that clearly state they are made from pasteurized milk; and do not eat meat spreads or smoked seafood from the refrigerated or deli section of the store (canned or shelf-stable products may be eaten).
Noroviruses (formerly called Norwalk virus or Norwalk-like viruses) are estimated to cause 23 million cases of acute gastroenteritis (commonly called the ‘stomach flu”) in the U.S. each year, and are the leading cause of gastroenteritis. Of viruses, only the common cold is reported more often than viral gastroenteritis (Norovirus).
Noroviruses may cause more outbreaks of foodborne illness than all bacteria and parasites. They can cause extended outbreaks because of their high infectivity, persistence in the environment, resistance to common disinfectants, and difficulty in controlling their transmission through routine sanitary measures.
The Norovirus is transmitted primarily through the fecal-oral route and fewer than 100 Norovirus particles are said to be needed to cause infection.
Transmission occurs either person-to-person or through contamination of food or water. Transmission can occur by touching surfaces or objects contaminated with Norovirus and then placing that hand in your mouth; having direct contact with another person who is infected and showing symptoms; sharing foods or eating utensils with someone who is ill; exposure to aerosolized vomit; and consuming food contaminated by an infected food handler.
The virus is shed in large numbers in the vomit and stool of infected individuals, most commonly while they are ill. Some individuals may continue to shed Norovirus up to two weeks after they have recovered from the illness.
Symptoms of a Norovirus infection
Usual symptoms of Norovirus infections include nausea, vomiting, diarrhea, and abdominal pain. Headache and low-grade fever may also accompany this infection. The illness is usually mild and brief. It will develop 24 to 48 hours after exposure and lasts for 24 to 60 hours. Recovery usually occurs in two to three days without serious or long-term health effects. Immunity is not permanent and reinfection can occur.
Diagnosis and treatment for Norovirus
Laboratory diagnosis is difficult. Diagnosis is often based on the combination of symptoms, particularly the prominence of vomiting, little fever, and the short duration of illness. Actual proof of infection requires research laboratory techniques in which Norovirus particles are identified by electron microscopy from samples of stool or vomitus.
No specific treatment is available. Persons who are severely dehydrated might need rehydration therapy.
Preventing a Norovirus infection
The good news about Norovirus is that it does not multiply in foods as many bacteria do. In addition, thorough cooking destroys this virus. To avoid this illness, make sure the food you eat is cooked completely. Shellfish (oysters, clams, mussels) pose the greatest risk and any particular serving may be contaminated; there is no way to detect a contaminated oyster from a safe oyster. With shellfish, only complete cooking offers reliable protection.
Wash raw vegetables thoroughly before eating or preparing salads. If you are traveling in an area that appears to have polluted water, drink only boiled drinks or carbonated bottled beverages without ice.
Wash hands with soap and warm water after using the toilet, before preparing or eating food; and after caring for the sick; exclude persons with gastroenteritis from the kitchen; and always dispose of sewage in a sanitary manner.
Salmonella is one of the most common enteric (intestinal) infections in the United States. Salmonellosis (the disease caused by Salmonella) is the second most common bacterial foodborne illness after Campylobacter infection. It is estimated that 1.4 million cases of salmonellosis occur each year in the U.S.; 95% of those cases are foodborne-related. Approximately 220 of each 1000 cases result in hospitalization and eight of every 1000 cases result in death. About 500 to 1,000 or 31% of all food-related deaths are caused by Salmonella infections each year. Salmonellosis is more common in the warmer months of the year.
Salmonella infection occurs when the bacteria are ingested, typically from food derived from infected food-animals, but it can also occur by ingesting the feces of an infected animal or person. Food sources include raw or undercooked eggs/egg products, raw milk or raw milk products, contaminated water, meat and meat products, and poultry. Raw fruits and vegetables contaminated during slicing have been implicated in several foodborne outbreaks.
Symptoms of a Salmonella infection
The acute symptoms of Salmonella gastroenteritis include the sudden onset of nausea, abdominal cramping, and bloody diarrhea with mucous. Fever is almost always present. Vomiting is less common than diarrhea. Headaches, myalgias (muscle pain), and arthralgias (joint pain) are often reported as well. The onset of symptoms usually occurs within 6 to 72 hours after the ingestion of the bacteria. The infectious dose is small, probably from 15 to 20 cells.
Reiter’s Syndrome, which includes and is sometimes referred to as ‘reactive arthritis,” is an uncommon, but debilitating, result of a Salmonella infection. The symptoms of Reiter’s Syndrome usually occur between one and three weeks after the infection. Reiter’s Syndrome is a disorder that causes at least two of three seemingly unrelated symptoms: reactive arthritis, conjunctivitis (eye irritation), and urinary tract infection. The arthritis associated with Reiter’s Syndrome typically affects the knees, ankles, and feet, causing pain and swelling. Wrists, fingers and other joints can be affected, though with less frequency. With Reiter’s Syndrome, the affected person commonly develops inflammation where the tendon attaches to the bone, a condition called enthesopathy. Some people also develop heel spurs, bony growths in the heel that cause chronic or long-lasting foot pain. Arthritis from Reiter’s Syndrome can also affect the joints of the back and cause spondylitis, inflammation of the vertebrae in the spinal column. The duration of reactive arthritis symptoms can vary greatly. Most of the literature suggests that the majority of affected persons recover within a year. The condition, can, however, be permanent. For more information, visit the Marler Clark sponsored Web site about Reiter’s Syndrome.
Detection and treatment of a Salmonella infection
Salmonella bacteria are discovered in stool cultures. Although blood cultures are rarely positive, bacteremia (bacteria in the blood stream) does occur in 5% of adults with Salmonella gastroenteritis and can result in spread to the heart (endocarditis), spleen, bone (osteomyelitis), and joints (Reiter’s Syndrome or reactive arthritis). However, blood cultures are often not performed and in most cases the blood stream is not infected. In the stool, the laboratory is challenged to pick out Salmonella from many other similar bacteria that are normally present. In addition, many persons submit cultures after they have started antibiotics, which may make it even more difficult for a microbiology lab to grow Salmonella. So, the diagnosis of salmonellosis may be problematic and many mild cases are culture negative.
Salmonella infections usually resolve in five to seven days, and many times require no treatment, unless the affected person becomes severely dehydrated or the infection spreads from the intestines. Persons with severe diarrhea may require rehydration, often with intravenous fluids. Treatment with antibiotics is not usually necessary, unless the infection spreads from the intestines, or otherwise persists, in which case the infection can be treated with ampicillin, gentamicin, trimethoprim/sulfamethoxazole, or ciprofloxacin. Some Salmonella bacteria have become resistant to antibiotics, possibly as a result of the use of antibiotics to promote the growth of feed animals.
For those persons who develop Reiter’s Syndrome, symptomatic treatment with high doses of a nonsteroidal anti-inflammatory drug and steroid injections into affected joints can be helpful in reactive arthritis. For people with severe joint inflammation, injections of corticosteroids directly into the affected joint may reduce inflammation. A small percentage of patients with reactive arthritis have severe symptoms that cannot be controlled with these treatments, in which case medicine that suppresses the immune system, such as sulfasalazine or methotrexate, may be effective. Exercise, when introduced gradually, may help improve joint function. Topical corticosteroids can be applied directly on the skin lesions associated with reactive arthritis.
Preventing a Salmonella infection
To prevent salmonellosis, cook poultry, ground beef, and eggs thoroughly before eating. In order to insure that eggs do not contain viable Salmonella they must be cooked at least until the yoke is solid, and meat and poultry must reach 160?F or greater throughout. Be particularly careful with foods prepared for infants, the elderly, and those with a compromised immune system.
Do not eat or drink foods containing raw eggs, such as homemade eggnog and hollandaise sauce. Avoid drinking raw (unpasteurized) milk or products made from raw milk.
Wash hands, kitchen work surfaces, and utensils with soap and water immediately after they have been in contact with foods of animal origin. Also, wash hands with soap after handling reptiles, amphibians or birds, or after contact with pet feces. Infants and immunocompromised persons should have no direct or indirect contact with such pets.
Shigella is a bacterium that can cause sudden and severe diarrhea (gastroenteritis) in humans. Shigellosis is the name of the disease that Shigella causes. The illness is also known as “bacillary dysentery.” Shigella bacteria can infect the intestinal tract after the ingestion of relatively few organisms. This is why shigellosis is the most communicable of the bacterial-induced diarrheas.
The source of Shigella bacteria is the excrement (feces) of an infected individual that is ultimately ingested by another person. The infectious material is spread to new cases by person-to-person contact or via contaminated food or water. Approximately 20% of the nearly 450,000 cases of shigellosis that occur annually in the U.S are foodborne-related. Generally, the food preparer is the individual who contaminates the food, but food may also become contaminated during processing. Contamination of drinking water by Shigella is a problem that more often occurs in the developing world, but swimming pools and beaches in the U.S. can become contaminated by infected individuals. No group of individuals is immune to shigellosis, but certain individuals are at increased risk, particularly small children. Persons infected with HIV experience shigellosis much more commonly than other individuals, but this may largely be due to an increased risk among men having sex with men.
Symptoms of a Shigella infection
Most people who are infected with Shigella develop diarrhea, fever, and abdominal cramps. Severity of the disease ranges from mild to very severe diarrhea. Diarrhea is bloody 25-50% of the time and most often contains mucus. Rectal spasms are common. The illness starts 12 hours to 6 days, usually 1 to 2 days, after exposure to the bacteria. Dehydration is also a common symptom.
Detection and treatment of a Shigella infection
A culture of an infected person’s stool sample can identify the Shigella bacteria. The laboratory can also do special tests to tell which species of Shigella the person has and which antibiotics would be best to treat it.
Although shigellosis is usually a self-limited illness, antibiotics can shorten the course, and in the most serious cases, might be life-saving. When therapy is indicated, a fluoroquinolone antibiotic is the recommended first-line treatment for non-pregnant adults, such as ciprofloxacin 500 mg twice daily for three days. Alternative antimicrobial agents include trimethoprim-sulfamethoxazole, azithromycin, and ceftriaxone. Antidiarrheal agents such as loperamide (Imodium) or diphenoxylate with atropine (Lomotil) are likely to make the illness worse and should be avoided.
While shigellosis usually resolves in 5 to 7 days, it may be several months before an affected person’s bowel habits are entirely normal. In some persons, especially young children, the elderly, and immune compromised persons, the diarrhea can be so severe that the affected person needs to be hospitalized. It is estimated that over 6,000 hospitalizations for shigellosis occur each year in the U.S. Complications of shigellosis include severe dehydration, seizures in small children, rectal bleeding, and invasion of the blood stream by the bacteria. In the U.S., it is estimated that about 70 persons die yearly from shigellosis, with small children and the elderly at greatest risk of dying.
Up to 3% of persons infected with Shigella may later develop a syndrome that includes joint pain and swelling, irritation of the eyes, and sometimes painful urination. This is a reaction to the previous gastroenteritis and is called ‘reactive arthritis” or Reiter’s Syndrome. Basically, the immune system, intending to fight Shigella, attacks the body’s cells. Reiter’s Syndrome is most common in persons with the human leukocyte antigen (HLA) B27 genetic makeup. Reiter’s Syndrome can last for months or years, can lead to chronic arthritis, and may be difficult to treat. See the Marler Clark sponsored site on Reiter’s Syndrome for more information.
How can a Shigella infection be prevented?
Frequent and careful hand washing with soap and water should be done by both the ill individual and anyone who is in contact with that person. Supervised hand washing of all children should be followed in day care centers and as soon as children return home. Young children with a Shigella infection, or with diarrhea of any cause, should not be in contact with uninfected children.
Everyone who changes an infected child’s diapers should be sure the diapers are disposed of properly in a closed-lid garbage can and should wash their hands carefully with soap and warm water immediately after changing the diapers. After use, the diaper changing area should be wiped down with disinfectant, such as household bleach.
Shigella organisms are killed by heat used in cooking. People who have shigellosis or any diarrhea should not prepare food for others until they have been shown to no longer be carrying the bacteria.
At swimming pools, maintaining a chlorine level of at least 0.5-PPM will kill Shigella. Children not yet toilet trained should be excluded from public swimming areas; stay clear if this rule is broken. Children with diarrhea should never be taken to public swimming areas.
Drink water only if it has been chlorinated (most tap water) or treated with ozone (most bottled water). Avoid drinking pool or beach water. Consume only pasteurized dairy products.
Simple precautions taken while traveling to the developing world can also prevent getting shigellosis: “boil it, cook it, peel it, or forget it”. Drink beverages only if they are canned/bottled in a sanitary environment, boiled (like coffee), or have been in contact with alcohol for a prolonged period (wine or beer, not mixed drinks). Do not use ice in beverages.