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Tuesday, March 12, 2013

Foodborne Diseases

Foodborne disease, also foodborne illness and colloquially referred to as food poisoning, is any illness resulting from the consumption of contaminated food, pathogenic bacteria, viruses, or parasites that contaminate food, as well as chemical or natural toxins such as poisonous mushrooms.

Infectious diseases spread through food or beverages are a common, distressing, and sometimes life-threatening problem for millions of people in the United States and around the world. The Centers for Disease Control and Prevention (CDC) estimates that each year in the United States, 1 in 6 Americans (or 48 million people) gets sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases.

Foodborne disease is extremely costly. Health experts estimate that the yearly cost of all foodborne diseases in this country is 5 to 6 billion dollars in direct medical expenses and lost productivity.

Created during the 1930s, this historic sign, explaining the benefits of safe food handling, was created by the Minnesota Department of Health. Its message was part of a campaign to promote food safety and to prevent food-borne illness. Source: Centers for Disease Control and Prevention (CDC) Public Health Image Library (PHIL) http://phil.cdc.gov/PHIL_Images/8582/8582_lores.jpg. Content Provider(s): CDC/ Minnesota Department of Health, R.N. Barr Library; Librarians Melissa Rethlefsen and Marie Jones. Copyright Restrictions: None - This image is in the public domain and thus free of any copyright restrictions.
There are more than 250 known foodborne diseases. They can be caused by bacteria, viruses, or parasites. Natural and manufactured chemicals in food products also can make people sick. Some diseases are caused by toxins (poisons) from the disease-causing microbe (germ), others by the human body’s reactions to the microbe itself. To better understand the epidemiology (study of disease origin and spread) of foodborne diseases in the United States, 10 states across the country are collecting annual data on the occurrence of new cases of the most common causes of bacterial and parasitic infections through the Foodborne Diseases Active Surveillance Network, a CDC-sponsored program known as the Foodborne Diseases Active Surveillance Network (FoodNet).


BOTULISM

Botulism is a rare but serious illness. Each year, U.S. healthcare providers report an average of 145 cases of botulism to the Centers for Disease Control and Prevention (CDC). Although there are several kinds of botulism, this topic will focus on botulism caused by eating contaminated food. About 10 to 30 outbreaks of foodborne botulism are reported annually to CDC. This illness does not occur frequently, but it can be fatal if not treated quickly and properly.

Cause
Botulism is caused by toxin (poison) produced by Clostridium botulinum bacteria. This toxin affects your nerves and, if untreated, can cause paralysis and respiratory failure. C. botulinum toxin is one of the most powerful naturally occuring toxins. Exposure to the toxin, particularly in an aerosolized (spray) form, can be fatal. C. botulinum has been made into bioweapons by rogue states and is one focus of current efforts to counter bioterrorism.

Transmission
Cases of foodborne botulism often originate with home-canned foods with low acid content, such as asparagus, green beans, beets, and corn. Clostridium botulinum, the bacterium that causes botulism, thrives in sealed containers because it is anaerobic, meaning it can survive and grow with little or no oxygen. Outbreaks of botulism, however, are often from more unusual sources such as baked potatoes wrapped in aluminum foil but not kept hot, and tomatoes.

Symptoms
Symptoms of foodborne botulism include:

  • Double vision and drooping eyelids
  • Slurred speech
  • Dry mouth and difficulty swallowing
  • Weak muscles

Symptoms usually begin within 18 to 36 hours after you eat contaminated food, but can occur in as few as 6 hours or as long as 10 days afterward.

Diagnosis
A healthcare provider can use laboratory tests to identify C. botulinum toxin in your blood or stool if you are infected.

Treatment
If you are diagnosed with botulism early, your healthcare provider can treat you successfully with an antitoxin that blocks the action of the bacterial toxin circulating in your blood. Although antitoxin keeps the disease from becoming worse, it will still take many weeks before you recover. Your healthcare provider may try to remove any contaminated food still in your gut by making you vomit or by giving you an enema.

Prevention
To prevent getting foodborne botulism you should:

  • Follow strict hygienic steps when canning foods at home
  • Refrigerate oils containing garlic or herbs
  • Keep baked potatoes wrapped in aluminum foil either hot until served or refrigerated
  • Consider boiling home-canned food before eating it to kill any bacteria lurking in the food

Complications
If left untreated, botulism can temporarily paralyze your arms, legs, trunk, and the muscles that help you breathe. The paralysis usually improves slowly over several weeks. People who develop severe botulism experience breathing failure and paralysis and need to be put on ventilators (breathing machines).

Research
Basic research is helping scientists to better understand how microbes (germs) spread by contaminated food or water cause disease in humans. The National Institute of Allergy and Infectious Diseases (NIAID)-supported researchers are studying the genes that help harmful bacteria to establish themselves in the human body and cause disease. For example, scientists have identified genes that appear to be involved in signaling certain immune system cells to cause inflammation and may contribute to the development of diarrhea.

Other NIAID-sponsored research focuses on understanding more about how bacteria grow and interact in cells. Scientists have discovered that some intestinal bacteria recognize when they are in a human and respond by activating a particular set of powerful genes that enable the bacteria to multiply in the body and cause disease. NIAID-sponsored studies are also in progress to discover new ways to prevent infection and treat people suffering from progressing disease.

Improving Treatments for Botulism
Researchers from Tufts University and Thomas Jefferson University have set out to find an improved way to treat and prevent botulism, a rare but serious paralytic illness. Botulism is caused by botulinum neurotoxins (BoNTs), which are produced by a bacterium called Clostridium botulinum. All forms of botulism lead to paralysis that typically starts with the facial muscles and then spreads towards the limbs. In severe forms, it leads to paralysis of the breathing muscles and causes respiratory failure.

There are three basic types of botulism—foodborne botulism, intestinal botulism (proliferation of the bacterium in the gut), and wound botulism (contamination of a wound by the bacterium). Each can be treated effectively with antitoxins if the agent is administered before the symptoms become severe. The treatment is usually produced by immunizing large animals with an inactivated form of BoNTs, which triggers the animal’s body to generate antitoxins to defend itself against the disease. The process of manufacturing the antitoxins into a usable form for humans is an expensive task, and the product has a limited shelf life.

Testing a new antitoxin stategy in mice, the research team found that a pool of four different small antitoxin binding agents could direct a single antibody (an infection-fighting protein) to become attached to the toxin at four sites and protect the mice from BoNT just as well as the conventional antitoxin-only treatment for botulism. Importantly, this combination treatment would be faster and more economical to produce, and easier to stockpile. With additional development, treatments such as this might be beneficial in treating other diseases as well, such as exposures to other toxins and venoms.

Reference: Sepulveda J, Mukherjee J, Tzipori S, Simpson L, Shoemaker C. Efficient Serum Clearance of Botulinum Neurotoxin Achieved Using a Pool of Small Antitoxin Binding Agents. Infection and Immunity. 2010 February; 78 (2): 756-763.

CAMPYLOBACTERIOSIS

Campylobacteriosis is an infectious disease caused by eating or handling contaminated food or drinking contaminated beverages. U.S. healthcare providers report more than 10,000 cases to the Centers for Disease Control and Prevention (CDC) yearly. CDC estimates 100 people die of the disease yearly. The disease occurs more frequently in summer than winter.

Cause
Campylobacteriosis is caused by bacteria called Campylobacter. Campylobacter jejuni, C. fetus, and C. coli are the types that usually cause the disease in people. C. jejuni causes most cases of this foodborne disease. According to the Centers for Disease Control and Prevention, C. jejuni is the leading cause of bacterial diarrheal illness in the United States, affecting about 2.4 million people every year. The bacteria cause between 5 and 14 percent of all diarrheal illness worldwide. C. jejuni primarily affects children less than 5 years old and young adults 15 to 29 years old.

Transmission
You can get infected with Campylobacter from handling raw poultry, eating undercooked poultry, drinking nonchlorinated water or raw milk, or handling infected human or animal feces. Most frequently, poultry and cattle waste are the sources of the bacteria, but feces from puppies, kittens, and birds also may be contaminated with the bacteria.

Symptoms
If you are infected with Campylobacter, you may have no symptoms. If you do, they can include:

  • Diarrhea (often bloody)
  • Abdominal cramping and pain
  • Nausea and vomiting
  • Fever
  • Tiredness

Campylobacteriosis usually lasts for 2 to 5 days, but in some cases as long as 10 days.

Diagnosis
Your healthcare provider can use laboratory tests to identify Campylobacter in your stool if you are infected.

Treatment
If you are like most people infected with Campylobacter, you will get better with no special treatment. If you need treatment, your health care provider can prescribe an antibiotic such as ciprofloxacin or azithromycin. Erythromycin helps treat diarrhea caused by Campylobacter. If you have diarrhea, be sure to drink plenty of water.

Prevention

  • Wash hands before preparing food
  • Wash hands immediately after handling raw poultry or other meat
  • Wash thoroughly with soap and hot water all food preparation surfaces and utensils that have come in contact with raw meat
  • Cook poultry products to an internal temperature of 170ºF for breast meat and 180ºF for thigh meat
  • Don’t drink unpasteurized milk
  • Don't drink unchlorinated water that isn’t boiled
  • Wash hands after handling pet feces or visiting petting zoos

Complications
Some people with campylobacteriosis have convulsions with fever or meningitis (inflammation of the lining of the spinal cord). Some people infected with Campylobacter develop arthritis.

A small number of people may develop Guillain-Barré Syndrome (GBS), the leading cause of acute paralysis in this country. This rare condition develops from 2 to 4 weeks after Campylobacter infection and usually after diarrheal symptoms have disappeared. People with GBS suffer from increasing paralysis of the limbs which lasts for several weeks. In more severe cases, they develop breathing problems requiring very long hospital stays.

Research
Basic research is helping scientists to better understand how microbes spread by contaminated food or water cause disease in humans.

NIAID-supported researchers are studying the bacterial genes that help pathogens (germs) establish themselves in the human body and cause disease. For example, scientists have identified genes that appear to be involved in signaling certain immune system cells to cause inflammation and may contribute to the development of diarrhea.

Other NIAID-sponsored research focuses on methods by which the organism grows and interacts in cells. Scientists have discovered that some intestinal bacteria recognize when they are in a human and respond by activating a particular set of powerful genes that enable the organism to live in the body and cause disease. Future studies will define new ways to intervene, whether by prevention or treatment, in the disease process.

Scientists have determined the complete genome (genetic blueprint) sequences for Salmonella typhi, S. typhimurium, C. jejuni, and Escherichia coli 0157:H7. Sequencing studies are under way for Shigella, Yersinia, as well as other harmful strains of E. coli. Scientists hope this new information will speed the discovery of new targets for treatments and vaccines against foodborne pathogens.

E. COLI

Hundreds of Escherichia coli (E. coli) strains are harmless, including those that thrive in the intestinal tracts of humans and other warm-blooded animals. These strains are part of the protective microbial community in the intestine and are essential for general health. Other strains cause serious poisoning in humans by making a toxin called Shiga toxin. These bacteria are called “Shiga toxin-producing” E. coli, or STEC for short. The most commonly identified STEC in North America is E. coli O157:H7, according to the Centers for Disease Control and Prevention (CDC). CDC estimates that 265,000 STEC infections occur each year in the United States. Approximately 36 percent of these infections are caused by E. coli O157:H7.

Cattle are the main sources of E. coli O157:H7, but these bacteria are also in other domestic and wild mammals. The bacteria often cause bloody diarrhea and can lead to kidney failure, especially in young children or in people with weakened immune systems. Most illness has been associated with contaminated food or water, contact with an infected person, or contact with animals that carry the bacteria.

In addition to E. coli O157:H7, there are other serotypes of E. coli, named enterohemorrhagic E. coli, that cause the same serious illnesses. Other forms of E. coli that cause diarrheal disease include:

  • Enterotoxigenic E. coli (ETEC) is a leading bacterial cause of diarrhea in the developing world. Each year, about 210 million cases and 380,000 deaths occur, mostly in children, from ETEC, according to the World Health Organization. ETEC is the most common cause of traveler's diarrhea and affects troops deployed overseas.
  • Enteropathogenic E. coli (EPEC) is a bacterial cause of persistent diarrhea that can last 2 weeks or more. It spreads to humans through contact with contaminated water or infected animals and is common in developing countries. In industrialized countries, the frequency of these organisms has decreased, but they continue to be an important cause of diarrhea, according to CDC.

Cause
While there are many types of E. coli bacteria, only certain types cause foodborne illness. Hundreds of harmless strains of E. coli can be found widely in nature, including the intestinal tracts of humans and other warm-blooded animals. Disease-causing strains, however, are a frequent cause of both intestinal and urinary-genital tract infections. In 1982, scientists identified the first harmful foodborne strain of E. coli in the United States. The disease-causing foodborne E. coli most commonly found in this country is called O157:H7, which refers to chemical compounds found on the bacterium’s surface. Cattle are the main sources of E. coli O157:H7, but these bacteria also can be found in other domestic and wild mammals.

Several different strains of harmful E. coli can cause diarrheal disease:

  • Particularly dangerous types of E. coli, such as E. coli O157:H7, produce one or more kinds of toxins (poisons) called Shiga toxins. Shiga toxins can severely damage the lining of your intestines and kidneys. These types of bacteria are called Shiga toxin-producing E. coli (STEC). STEC often causes bloody diarrhea and can lead to kidney failure in children or in people with weakened immune systems.
  • Enterotoxigenic E. coli (ETEC), which produce a different toxin, can cause diarrhea. These strains typically cause so-called travelers’ diarrhea because they commonly contaminate food and water in developing countries.
  • Enteropathogenic E. coli (EPEC) cause persistent diarrhea (lasting 2 weeks or more) and are more common in developing countries where they can be transmitted to humans through contaminated water or contact with infected animals.

Other types of E. coli, including O26:H11 and O111:H8, also have been found in the United States and can cause disease in people.

Transmission
Shiga toxin-producing E. coli (STEC) occurs when people consume contaminated foods or liquids. The U.S. Department of Agriculture Food Safety and Inspection Service recall site lists food products contaminated with harmful E. coli.

The most common contaminated foods and liquids that have caused E. coli outbreaks include:

  • Undercooked or raw hamburgers
  • Salami
  • Produce such as spinach, lettuce, sprouted seeds
  • Unpasteurized milk, apple juice, and apple cider
  • Contaminated well water or surface water frequented by animals

STEC can also occur by:

  • Failure to wash your hands thoroughly with soap and water following contact with an infected animal or animal waste. This can occur at farms, petting zoos, fairs, or even in your own backyard.
  • Failure to wash your hands thoroughly with soap and water following contact with an infected person
  • Swallowing unchlorinated or underchlorinated water in swimming pools contaminated by human feces
  • Swimming in water with even very low levels of sewage contamination
  • Consuming contaminated food, water, or ice

Symptoms
Shiga toxin-producing E. coli (STEC) can cause the following symptoms:

  • Nausea
  • Severe abdominal cramps
  • Watery or very bloody diarrhea
  • Fatigue

STEC can also cause low-grade fever or vomiting. Symptoms usually begin from 2 to 5 days after eating contaminated food or drinking contaminated liquids. Symptoms may last for 8 days, and most people recover completely from the disease.

Diagnosis
The Centers for Disease Control and Prevention recommends testing anyone who suddenly develops diarrhea with symptoms of bloody stool. Healthcare providers use lab tests to identify Shiga toxin-producing E. coli in stool samples.

Treatment
According to the Centers for Disease Control and Prevention, early supportive treatment is important for people with E. coli infection, especially those who have Shiga toxin-producing E. coli (STEC). There is no evidence that treatment with antibiotics is helpful, and taking antibiotics may increase the risk of hemolytic uremic syndrome, a serious complication of STEC that can lead to kidney failure.

Prevention
According to the Centers for Disease Control and Prevention, to prevent Shiga toxin-producing E. coli (STEC) infection, you should:

  • Wash your hands thoroughly after going to the bathroom or changing diapers
  • Wash your hands thoroughly after handling animals, animal bedding, or any material contaminated with animal fecal matter
  • Eat only thoroughly cooked ground beef, pork, sheep meat, or sausage
  • Cook ground meat products to an internal temperature of 160ºF
  • Avoid drinking unpasteurized milk and juices
  • Wash fresh fruits and vegetables thoroughly before eating raw
  • Prevent cross contamination in food preparation areas by washing hands, counters, cutting boards, and utensils after they touch raw meat
  • Keep raw meat separate from ready-to-eat foods

Complications
Hemolytic uremic syndrome (HUS), a serious complication of Shiga toxin-producing E. coli (STEC), can lead to kidney failure and death. Children are particularly prone to this complication, and HUS is the most common cause of acute kidney failure In North America. Blood transfusions and kidney dialysis, performed in the intensive care unit of a hospital, are needed to treat this life-threatening condition. About 8 percent of people with HUS have other lifelong complications, such as high blood pressure, seizures, blindness, paralysis, and the effects of having part of their intestines removed.

Research
NIAID supports research to understand how Escherichia coli bacteria, better known as E. coli, cause illness and identify the best possible treatments for people with E. coli infections. Multiple teams of scientists are looking into how E. coli causes disease, including Enterohemmaorrhagic Shiga toxin-producing E. coli (known to scientists as EHEC/STEC). EHEC/STEC causes severe disease, and sometimes death. Researchers are uncovering the basic mechanisms of how the bacteria damages human cells and systems, and identifying factors associated with the severest forms of the disease.

By studying the human genome, researchers have identified special, small molecules that stop bacteria from producing toxins and other molecules that can cause a severe bacterial infection and illness or death. NIAID-funded research has uncovered complex communication systems in bacteria that allow pathogens such as E. coli 0157:H7 to hide until the bacteria launch coordinated attacks with overwhelming numbers of bacteria.

Other researchers have discovered that antibiotic therapy does not help people with bloody diarrhea, and can even cause more harm during some types of severe infections.

Researchers are designing and testing monoclonal antibodies and other therapies to treat STEC infection before it progresses into severe, life-threatening forms. NIAID also provides funding to develop models for testing potential medicines before they are used in human clinical trials.

HEPATITIS A

Hepatitis A is a contagious, acute inflammatory disease of the liver. The Centers for Disease Control and Prevention estimates that nearly 25,000 people contracted hepatitis A in the United States in 2007, although the number of reported cases is much lower because some people do not show symptoms. Most people who contract hepatitis A will recover completely, but an estimated 100 people die from the infection every year in the United States.

Causes
Hepatitis A is caused by the hepatitis A virus, which is found in the stool and blood of an infected person.

Transmission
People become infected with hepatitis A when they orally ingest the fecal matter—even just microscopic traces—of infected individuals. This usually happens in one of two ways:

  • Close contact with an infected person who has not washed his or her hands after using the bathroom
  • Consuming food or water contaminated with the virus, usually caused by food handlers who are infected and do not thoroughly wash their hands or who wash food with contaminated water

Hepatitis A is common in certain areas of the world where there is poor sanitation. Several outbreaks in the United States and elsewhere have also been associated with injecting and non-injecting drug use.

Symptoms
Hepatitis A does not always cause obvious symptoms. Some people may experience mild symptoms lasting 1 to 2 weeks, while others will have more severe symptoms that can last for several months. Generally, the severity of the illness increases with age, which is why children infected with the hepatitis A virus usually do not show any symptoms. Symptoms of hepatitis A include the following:

  • Jaundice
  • Fatigue
  • Abdominal pain
  • Nausea and vomiting
  • Diarrhea
  • Fever
  • Loss of appetite
  • Dark urine

Symptoms can appear anywhere from 2 to 6 weeks after exposure. However, it’s important to note that infected people are contagious up to 2 weeks before they show any symptoms at all.

Transmission
People become infected with hepatitis A when they orally ingest the fecal matter—even just microscopic traces—of infected individuals. This usually happens in one of two ways:

  • Close contact with an infected person who has not washed his or her hands after using the bathroom
  • Consuming food or water contaminated with the virus, usually caused by food handlers who are infected and do not thoroughly wash their hands or who wash food with contaminated water

Hepatitis A is common in certain areas of the world where there is poor sanitation. Several outbreaks in the United States and elsewhere have also been associated with injecting and non-injecting drug use.

Diagnosis
Healthcare providers review symptoms and can diagnose hepatitis A with a blood test, which will reveal the presence of antibodies to hepatitis A virus.

Treatment
There are no medicines for treating hepatitis A after you get infected. If you have a mild case, your healthcare provider will probably prescribe rest, plenty of fluids, and a nutritious diet. While your body fights hepatitis A, you should avoid any medicines—over-the-counter or prescribed—that could damage your liver. You should also avoid alcohol during the recovery period, because alcohol also may damage your liver.

Prevention
Hepatitis A: The best way to prevent hepatitis A is to be vaccinated. The vaccine has been available since the 1990s, and health experts recommend it for travelers going to Africa, Asia, Central and South America, or Eastern Europe. Healthcare providers may encourage patients with certain allergic conditions and pregnant women to avoid the vaccine. If you aren't vaccinated, the best ways to prevent hepatitis A infection are by practicing good sanitation and hygiene and avoiding contaminated food and water, especially when traveling in countries where hepatitis A is common. Taking immunoglobulin (a protein that fights infection) will help keep you from getting sick if you have been exposed to hepatitis A virus during an outbreak.

Research
NIAID supports and conducts research on each of the five known hepatitis viruses—A, B, C, D and E. During the past 60 years, NIAID-supported investigators have been involved in many important breakthroughs in hepatitis research, including the discovery of the hepatitis A and E viruses, the development of one of the first diagnostic tests for hepatitis A, and studies that led to the creation of the hepatitis A vaccine and laid the foundation for advanced development of a hepatitis E vaccine. In addition to basic research to understand the molecular processes of hepatitis infection, our research involves significant focus on the development of new treatments and vaccines to prevent acute and chronic hepatitis infection.

NOROVIRUS INFECTION

Noroviruses, including Norwalk, Snow Mountain, and Hawaii viruses, cause an illness in humans called gastroenteritis. Gastroenteritis is an inflammation of the stomach and intestines. Sometimes misnamed "stomach flu," gastroenteritis is not related to flu (influenza), a respiratory illness caused by influenza virus.

Noroviruses are very contagious. They usually are found in contaminated food or drinks, but they also can live on surfaces or be spread through contact with an infected person. Each year in the United States, 23 million norovirus infections result in an estimated 50,000 hospitalizations and 310 deaths, according to the Centers for Disease Control and Prevention (CDC).

Cause
The main viruses that cause gastroenteritis used to be called "Norwalk-like viruses" because Norwalk is the most well-known virus in this group. Now the viruses are referred to as noroviruses.

Noroviruses are not new, but interest in them is growing as researchers learn how frequently they make people sick. Norovirus infections are implicated in newsworthy descriptions of outbreaks on military and cruise ships and in hotels, restaurants, daycare centers, nursing homes, and hospitals. Decontamination of these places has proved to be challenging.

Noroviruses are not related to bacteria or parasites that also can cause gastrointestinal illnesses.

Transmission
You can get norovirus infection by:

  • Eating food or drinking liquids contaminated by a food handler infected with the virus
  • Touching surfaces or objects contaminated with a norovirus, and then putting your hands in your mouth
  • Having direct contact with someone infected with a norovirus, such as caring for or sharing food or eating utensils with someone sick with norovirus
  • Eating improperly cooked contaminated shellfish, especially oysters
  • Eating improperly prepared uncooked fruits and vegetables
  • Drinking contaminated water

Noroviruses are found in the stool or vomit of people who are infected. If you have been infected with a norovirus, you can continue to transmit it to others even when you no longer have symptoms.

Symptoms
Because there are so many types of noroviruses, you can become infected and show symptoms many times. Symptoms of gastroenteritis caused by noroviruses can include:

  • Nausea
  • Abdominal cramps
  • Vomiting
  • Diarrhea
  • Headache
  • Fatigue
  • Fever
  • Muscle aches

Symptoms usually develop within hours or a few days after you are infected with a norovirus. It usually takes a couple of days before you are better.

Diagnosis
Your healthcare provider can use laboratory tests to diagnose norovirus infection, but these tests are not used routinely. Usually, your healthcare provider will diagnose it by examining you and noting your symptoms.

Treatment
The best treatments for norovirus infection are to get plenty of bed rest and drink lots of fluids. To prevent dehydration (severe loss of body fluids), your healthcare provider may give you specific instructions about the type of fluids you should drink. You should not take antibiotics for norovirus infection because they have no effect on viruses. If your infant or child has diarrhea, you should contact a healthcare provider immediately for treatment advice.

Prevention
To prevent norovirus you should:

  • Wash your hands with soap and water frequently. This is especially important for food handlers and caregivers
  • Prepare fresh and frozen foods safely, including thoroughly washing fresh produce
  • Disinfect contaminated surfaces in your kitchen and bathrooms with household chlorine bleach-based cleaners to kill viruses resting on surfaces
  • Wash contaminated clothing, diapers, sheets, and towels promptly in hot water (above 140ºF) and/or with bleach
  • Choose wisely when eating or drinking outside your home. If you aren't sure whether the food or water is safe, avoid it

In addition, you should not prepare food for others if you have norovirus infection.

Currently, there is no vaccine to protect you from norovirus infections.

Research
NIAID conducts research on foodborne viruses that cause diarrhea, such as caliciviruses (which include noroviruses), rotavirus, astrovirus, and hepatitis A and hepatitis E viruses.

NIAID scientist Albert Kapikian is recognized as "the father of human gastroenteritis virus research." In 1972, Dr. Kapikian identified the Norwalk virus, the first virus associated with acute epidemic gastroenteritis.

Today, NIAID supports research to develop vaccines against noroviruses and to enhance scientific understanding of norovirus pathogenicity (the disease-producing capacity of the virus) and the body's response. For example, researchers are examining genetic differences in response to norovirus infection as some people are more susceptible to succumbing to diarrhea and vomiting upon infection while others are not. In addition, NIAID-supported researchers are making progress in determining what makes different strains of noroviruses pathogenic.

NIAID also supports research to generate vaccine candidates against several different norovirus strains. Current studies are trying to produce new vaccines including edible vaccines against Norwalk virus and hepatitis A and hepatitis E viruses.

SALMONELLOSIS

Salmonellosis, or salmonella, is one of the most common foodborne diseases. Overall, salmonella infections are decreasing in the United States, but some types are still increasing.

Salmonella may occur in small, contained outbreaks in the general population or in large outbreaks in hospitals, restaurants, or institutions housing children or the elderly. While the disease is found worldwide, health experts most often report cases in North America and Europe. Every year, the Centers for Disease Control and Prevention (CDC) receives reports of 40,000 cases of salmonellosis in the United States.

Children are the most likely to get salmonellosis. The elderly, infants, and those with compromised immune systems are more likely to have a severe illness. People with AIDS are particularly vulnerable, often suffering from recurring episodes.

Cause
Many types of Salmonella bacteria cause salmonellosis in animals and people. While the occurrence of different types of Salmonella varies from country to country, S. typhimurium and S. enteritidis are the two most commonly found in the United States. Some strains of Salmonella have become resistant to several antibiotics normally used to treat people with salmonella disease, posing a serious public health threat.

Transmission
Salmonella bacteria can be found in food products such as raw poultry, eggs, and beef, and sometimes on unwashed fruit. Food prepared on surfaces that previously were in contact with raw meat or meat products can, in turn, become contaminated with the bacteria. This is called cross-contamination.

In recent years, the Centers for the Disease Control and Prevention (CDC) has received reports of several cases of salmonella from eating raw alfalfa sprouts grown in contaminated soil. You also can get salmonella after handling pets, particularly reptiles like snakes, turtles, and lizards.

Salmonella can become a chronic infection even if you do not have symptoms. In addition, though you may have no symptoms, you can spread the disease by not washing your hands before preparing food for others. In fact, if you know you have salmonella, health care experts recommend you do not prepare food or pour water for others until laboratory tests show you no longer carry Salmonella bacteria. 

Symptoms
The following symptoms usually begin from 12 hours to 3 days after you are infected:

  • Diarrhea
  • Fever
  • Abdominal cramps
  • Headache

These symptoms, along with possible nausea, loss of appetite, and vomiting, usually last for four to seven days.

Symptoms are most severe in the elderly, infants, and people with chronic conditions such as diabetes or HIV infection.

Diagnosis
Your healthcare provider can use lab tests that will identify Salmonella in your stool if you are infected.

Treatment
If you are like most people with salmonella, the disease will clear up within five to seven days and you won’t need to be treated. If you have severe diarrhea, however, you may need intravenous fluids. If the disease spreads from your intestines into your bloodstream, your healthcare provider can treat it with antibiotics such as ampicillin. Some strains of Salmonella have become resistant to several antibiotics normally used to treat people with salmonella disease, posing a serious public health threat.

Prevention
To prevent getting salmonella:

  • Don’t drink milk that is unpasteurized
  • Don’t eat foods containing raw eggs, such as homemade caesar salad dressing, cookie dough, and hollandaise sauce, or drink homemade eggnog made with raw eggs
  • Handle raw eggs carefully
  • Keep eggs refrigerated
  • Throw away cracked or dirty eggs
  • Cook eggs thoroughly
  • Cook poultry products to an internal temperature of 170ºF for breast meat and 180ºF for thigh meat
  • Wash thoroughly with soap and hot water all food preparation surfaces and utensils that have come in contact with raw poultry or raw eggs
  • Wash hands immediately after handling raw poultry or raw eggs
  • Wash hands immediately after handling reptiles and pets or having contact with pet feces. 

Complications
Reiter’s Syndrome - While most people recover successfully from salmonella, a few may develop a chronic condition called Reiter’s syndrome. This syndrome can last for months or years and can lead to arthritis. Its symptoms are painful joints, irritated eyes, and painful urination.

Unless treated properly, Salmonella bacteria can escape from the intestine and spread by blood to other organs, sometimes leading to death.

Typhoid Fever - Salmonella typhi bacteria can cause typhoid fever, a more serious disease. This disease, which can be fatal if untreated, is not common in the United States. Typhoid fever frequently occurs in developing countries, where it affects about 21.5 million persons each year, typically through contaminated water. According to the Centers for Disease Control and Prevention, about 400 cases occur each year in the United States, and 75 percent of these are acquired while traveling internationally.

Appropriate antibiotics usually are effective for treating typhoid fever, although the number of cases of antibiotic-resistant S. typhi are increasing in some parts of the world.

Currently, two vaccines are available in the United States that are 50 to 80 percent effective in preventing Salmonella typhi. The Typhoid Vaccine Live Oral Ty21a is given orally in several doses to immunize adults and children older than 6 years of age. The Vi capsular polysaccharide vaccine (or ViCPS) is an injected vaccine used in adults and in children over 2 years of age. Health experts do not recomment routine vaccination with either vaccine in the United States. Vaccination is recommended for travelers visiting areas where there is a risk of getting of S. typhi infection.

Research
Basic research is helping scientists to better understand how microbes spread by contaminated food or water cause disease in humans.

NIAID-supported researchers are studying the bacterial genes that help pathogens (germs) establish themselves in the human body and cause disease. For example, scientists have identified genes that appear to be involved in signaling certain immune system cells to cause inflammation and may contribute to the development of diarrhea. The genetic characteristics of outbreak strains are also being investigated.

Recently, a NIAID-funded study on the gut inflammation caused by Salmonella typhimurium was named the top paper of 2010 by The Scientist Faculty of 1000. This study found that the infecting bacterium benefits from the host’s immune response, gaining energy from it. Other infectious bacteria may soon be found to behave the same way.

Other NIAID-sponsored research focuses on methods by which the organism grows and interacts in cells. Scientists have discovered that some intestinal bacteria recognize when they are in a human and respond by activating a particular set of powerful genes that enable the organism to live in the body and cause disease. Future studies will define new ways to intervene, whether by prevention or treatment, in the disease process.

Scientists have determined the complete genome (genetic blueprint) sequences for Salmonella typhi, Salmonella typhimurium, Escherichia coli O157:H7, Shigella flexneri, Yersinia enterocolitica,and Campylobacter jejuni. Sequencing studies are underway for other harmful strains of these bacteria. Scientists hope this new information will speed the discovery of new targets for treatments and vaccines against foodborne pathogens.

NIAID is also supporting the [Systems Biology for EnteroPathogens program http://www.niaid.nih.gov/LabsAndResources/resources/dmid/sb/Pages/enteropathogens.aspx], established to deepen researchers’ fundamental understanding of the complex processes of microbes and their interactions with the host. The systems approach involves the use of advanced technologies to analyze, identify, quantify, model, and ultimately predict the overall molecular processes involved in the pathogenesis of Salmonella.

NIAID has awarded four grants to establish the [Enteric Research Investigational Network (ERIN) http://www.niaid.nih.gov/about/organization/dmid/clinical/Pages/erin.aspx], which is designed to bridge gaps between basic and clinical research on bacteria and viruses that gain access to the host via the gastrointestinal tract to cause a variety of diseases.

SHIGELLOSIS

Shigellosis is an intestinal infectious disease that is spread primarily through consumption of contaminated food and water. Transmission also can occur via person-to-person contact or by handling contaminated surfaces. Estimates on the number of shigellosis cases vary, as many mild cases often are not diagnosed or reported. A study of major pathogens that caused foodborne disease in the United States, mostly from 2000-2008, estimated that approximately 131,000 episodes of acquired foodborne infection with Shigella occurred each year, with 20 percent of these patients requiring hospitalization.

Cause
Shigellosis is caused by Shigella bacteria. There are four groups of Shigella that cause infection in humans: Shigella sonnei, S. dysenteriae, S. flexneri, and S. boydii. S. sonnei is the most common type of Shigella in developed countries, including the United States. Outbreaks of shigellosis frequently occur in tropical or temperate climates, especially in areas with severe crowding or poor hygiene. Outbreaks sometimes occur in daycare and institutional settings.

Transmission
You can be infected with Shigella by:

  • Eating food or drinking beverages contaminated by food handlers infected with Shigella who did not wash their hands properly after using the bathroom
  • Eating vegetables grown in fields containing contaminated sewage
  • Eating food contaminated by flies that bred in or contacted infected feces
  • Drinking or swimming in contaminated water

Ingestion of an extremely low number of bacteria, 10 to 100, can cause infection. If you are infected with Shigella, you can still pass the bacteria to others even if you have no symptoms of shigellosis. Toddlers and small children under the age of five are at highest risk for infection with shigellosis; many cases are spread in child daycare settings or among families with small children.

If you know you have shigellosis, you should not prepare food or beverages for others until laboratory tests show that you no longer carry Shigella bacteria.

Symptoms
Symptoms of shigellosis include:

  • Fever
  • Tiredness
  • Watery or bloody diarrhea
  • Nausea and vomiting
  • Abdominal pain

Symptoms usually begin within 2 days after you come in contact with Shigella. You usually get better within 5 to 7 days.

Diagnosis
Laboratory tests can identify the presence of Shigella in your stool if you are infected. The laboratory can also do special tests to tell which type of Shigella you have and which antibiotics, if any, would be best to treat it.

Treatment
If you have a mild infection, you should get better quickly without taking medicine. If you need to be treated, your healthcare provider usually will prescribe an antibiotic such as ampicillin or ciprofloxacin. Antidiarrheal medicines may make the illness worse because they do stop the diarrhea, but do not kill the bacteria in your intestine.

Prevention
To prevent getting shigellosis you should:

  • Wash your hands with soap and water before preparing foods and beverages
  • Wash your hands after using the bathroom or changing infant diapers
  • Disinfect diaper-changing areas after use
  • Help young children wash their hands carefully after they use the bathroom
  • Avoid swallowing swimming pool water

Complications
People who have symptoms of diarrhea usually recover completely, although their bowel habits may not return to normal until several months later.

  • Hemolytic Uremic Syndrome - S. dysenteriae type 1 bacteria produce Shiga toxin (poison), which can severely damage the lining of your intestines and kidneys. This toxin can cause life-threatening hemolytic uremic syndrome (HUS), which can lead to kidney failure. In North America, HUS is the most common cause of acute kidney failure in children, who are particularly prone to this complication. This condition is usually treated in an intensive care unit of a hospital, sometimes with blood transfusions and kidney dialysis. About 8 percent of people with HUS have other lifelong complications, such as high blood pressure, seizures, blindness, paralysis, and the effects of having part of their intestines removed due to the disease.
  • Reiter's Syndrome - S. flexneri infection can progress to Reiter’s syndrome, which can last for months or years and can lead to chronic arthritis. Its symptoms are painful joints, irritated eyes, and painful urination.

Research

The NIAID supports research to study how bacterial pathogens (germs) cause disease when they infect, colonize, and then interact with the human host's body. For example, scientists have discovered that some bacteria can recognize that they are inside the intestinal tract and then activate an important set of their genes that enable them to live in the body and cause disease. Other NIAID-sponsored research focuses on how the organism grows and interacts inside the human cell.

Scientists have identified genes that permit Shigella to obtain iron, an essential nutrient, from the human body. In addition, scientists have identified genes that appear to be involved in signaling certain immune system cells to cause inflammation, which may contribute to the development of diarrhea. Investigators are further defining the ways by which the toxins produced by Shigella result in the kidney damage leading to hemolytic uremic syndrome (HUS), a life-threatening condition. The primary goal of this research is to better understand how this kidney disease progresses. Future studies like these might define new ways to intervene, whether by prevention or treatment, in the disease process.

Recently, scientists have determined the complete genome sequences (genetic blueprint) for Shigella flexneri, as well as other major enteric bacteria. Scientists hope that sequencing information will speed the discovery of new targets for treatments and vaccines against foodborne pathogens.

NIAID-supported researchers are investigating small molecules that inhibit bacterial components that are critical for the development of shigellosis; these small molecules act through novel mechanisms that hopefully will not lead to the emergence of drug resistance that can occur with the use of antibiotics. Small molecules currently under study act to limit damage to the intestine, to prevent bacteria from obtaining essential nutrients, and to prevent the transport of bacterial proteins to the bacterial cell surface where they interact with the host cell in a variety of ways to cause disease.

Researchers are developing vaccines to prevent Shigella infections in humans. Scientists also are developing and testing monoclonal antibodies to combat the effects of Shiga toxin. These and other clinical studies are geared towards protecting the public from this diarrheal disease and towards improving the general public health.

References

Food-related disease information from CDC.
Foodborne Diseases Active Surveillance Network, a CDC-sponsored program known as FoodNet.
U.S. Food and Drug Administration (FDA).
U.S. Department of Agriculture (USDA).
U.S. Environmental Protection Agency (EPA).
U.S. Department of Health and Human Services.
Healthfinder.gov.
National Institutes of Health (NIH).
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).
National Institiute of Allergy and Infectious Diseases (NIAID).

Disclaimer - Information
These statements have not been approved by the U.S. Food and Drug Administration (FDA). This information is not intended to diagnose, treat, cure or prevent any disease.

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