The Centers for Disease Control and Prevention (CDC) estimates that more than 76 million incidents of foodborne illness occur in the United States each year.  Many of these cases are slight enough to not merit a visit to the doctor and go unreported.  However, about 5,000 deaths per year are associated with contaminated food.

Knowing the symptoms of foodborne illness can help save your life; it can also keep you from spreading diseases to others.  Many foodborne pathogens are easily transferred from person-to-person via contaminated surfaces and foods.

This following list is not intended to diagnose foodborne illnesses.  If you believe something you ate or drank has made you sick, seek medical help.  That important step can shorten the duration of your symptoms and may keep you from suffering potentially long-term complications associated with enteric (intestinal) diseases.  Severe infections of the intestine, especially by strong toxins and tissue-invading pathogens, can lead to chronic gastrointestinal problems such as Irritable Bowel Syndrome (IBS).

And some foodborne illnesses begin with gastrointestinal distress but can advance to systemic infections and become fatal.

Getting to a doctor also aids in providing information to help prevent others from becoming sick.  The faster an outbreak of foodborne illness is recognized, the faster public health officials and medical professionals can respond to prevent an epidemic and treat the sick, respectively.  A laboratory analysis of blood or stool samples can help determine if local or national food and water supplies are unsafe.

The list below describes the cause of the most common foodborne illnesses in the U.S. as well as the symptoms, usual sources, incubation periods, treatments, and potential complications.

Because the information describes a typical infection, it may not apply to each individual experience of foodborne illness.

Common Foodborne Pathogens and Toxins in the U.S.:

Anisakis simplex:  Anisakisis is caused by ingesting a larval stage of a marine roundworm in undercooked or raw marine fish.  Initial symptoms begin within hours of eating the seafood.  These include severe abdominal pain, vomiting, and nausea.  Because the worms initially remain in the upper digestive tract, the worm can be “coughed up.”  If the worms pass into the intestines they can cause symptoms resembling Crohn’s Disease 1-2 weeks after infection.  Diagnosis and treatment is done by removing larvae visualized during gastroscopic examination.

Bacillus cereus:  There are two types of B. cereus illnesses: vomit-inducing and diarrheal;  both are caused by bacteria that secrete an enterotoxin.   The average incubation period for the vomit-inducing type is 2-4 hours, while the diarrheal type can take up to 16 hours to manifest symptoms.  Boiled or fried rice dishes are commonly associated with the vomit-inducing type, while custards, sauces, meatloaf, cereal products, and refried beans typically contain the diarrheal type.

Campylobacter jejuni:  Sometimes referred to as “Campy,” this is one of the most common foodborne illnesses, affecting 2.4 million people in the U.S each year.  It is usually found in unpasteurized (raw) milk products, poultry, water, raw clams, and beef liver.  Diarrhea, bloody diarrhea, abdominal cramps, fever and headache begin after an average 2-5 day incubation period, but can take up to 10 days.  Most cases of Campylobacter require only supportive care and rehydration fluids.  Severe cases can require antibiotics.  Guillain-barre syndrome (GBS), a paralytic disease of the peripheral nervous system, can develop as a post-infection complication in about 1 in every 1,000 cases.

Clostridium botulinum:  This bacteria secretes a neurotoxin into the food it grows in. When ingested, it can cause a multitude of symptoms including diarrhea, blurred vision, vomiting, descending paralysis, and possible death.  Botulism grows in low-acid canned foods, smoked fish, baked potatoes, incompletely fermented marine mammals, garlic stored in oil, and shrink-wrapped mushrooms.  Symptoms can begin from 2 hours to 8 days after consumption of the toxin.  Treatment with an equine-derived antitoxin can stop progression of symptoms, as can removal of contaminated food through induced vomiting and enemas, but supportive care is usually necessary for weeks.  A second type of botulism poisoning can occur when infants eat C. botulinum spores.  Babies become lethargic, stop feeding, become constipated and paralysis sets in.  The most commonly contaminated food–honey–should not be fed to infants.  A human-derived antitoxin is used in conjunction with supportive care in these cases.

Clostridium perfringens:  C. perfringens is an entertoxin-secreting bacteria most often found in inadequately heated or reheated meats, meat pies, stews, gravy, sauces, and refried beans.  The incubation period averages 8-12 hours, after which diarrhea and abdominal cramps begin.  C. perfringens symptoms usually persist for one day.  A severe complication, necrotic enteritis (also known as pig-bel syndrome), can develop if large numbers of bacteria are ingested.

Cryptosporidium parvum:  Cryptosporidiosis is caused by ingesting fecally contaminated food or water; the largest outbreaks have occurred due to contaminated recreational water facilities.  Spores of this parasite are deposed in infected feces and can live for months outside a host.  Upon ingestion, the spores leave their dormant state and become active in the intestines.  Symptoms, which usually occur about a week after infection, include profuse watery diarrhea, nausea, vomiting, abdominal cramps and fever, lasting for a few days and sometimes resolving without medicine.  Over-the-counter anti-diarrheal medicines can help relieve the distress.  Immunocompromised people are at risk of chronic infections.

Cyclospora cayetanensis:  Cyclospora cayetanensis is a single-celled, intracellular parasite transmitted via fecally contaminated food and water.  Symptoms begin around one week after infection and include fatigue and watery diarrhea.  These can last from a few days to a month, and some patients relapse until the infection is cleared.  C. cayetanensis is considered a cause of “traveler’s diarrhea,” although outbreaks in North America have occurred due to contaminated imported foods.  After diagnosis from a positive stool culture, sulfa antibiotics are often prescribed.  No non-sulfa drugs have proven effective.

Entamoeba histolytica:  Entomoeba histolytica infections cause a range of diarrheal illness from mild, chronic diarrhea to fulminant ameobic dysentery.  The single-celled parasite enters the body via fecally contaminated food or water and invades the tissue of the intestines.  This can lead to bloody diarrhea but, more dangerously, the amoeba can enter the bloodstream and infect other vital organs.  Potentially fatal liver abscesses develop in a small number of untreated patients.  Gastrointestinal symptoms develop in only 10-20 percent of  those infected, usually within 2-4 weeks after infection but several months of incubation is possible.  People in tropical regions with poor sanitation and homosexual men are at the highest risk of E. histolytica infection.  Diagnosis of E. histolytica remains difficult because in stool samples it resembles a non-pathogenic amoeba E. dispar.  One antibiotic is prescribed to clear the infection if there are no symptoms, and two are used if there are symptoms.

Escherichia coli O157:H7 (STEC):  E. coli O157:H7 is a strain of E. coli that produces Shiga-like toxin.  It is found in fecally contaminated undercooked ground beef, water, unpasteurized milk or juice, and soft cheeses.  The bacteria colonize the intestine causing cellular destruction that leads to nausea, vomiting, diarrhea, bloody diarrhea and cramps.  Symptoms of E. coli O157:H7 infections usually manifest 48-96 hours after infection.  Hemolytic Uremic Syndrome (HUS) occurs when the toxins destroy the glomurelar endothelium,  the lining of the blood vessels where the blood is filtered in the kidney, leading to renal failure.  Treatment includes anti-diarrheal medications and supportive care.  Antibiotics should not be given as these increase the risk of HUS.  More information on this topic can be found here and here.

Escherichia coli (enterotoxigenic – ETEC):  E. coli strains that produce enterotoxin, either heat stabile and heat libile, cause this type of infection.  It is the main cause of “traveler’s diarrhea,” and the leading cause of diarrhea in the developing world.  Symptoms, such as nausea, vomiting, diarrhea, bloody diarrhea, abdominal cramps, stiff neck and confusion, begin after an incubation period of around 10-12 hours and last for 3 to 5 days.  The toxin secreted by the bacteria induces the lining of the intestine to, in turn, secrete more fluid leading to diarrhea and dehydration.  These bacteria are found most often in undercooked vegetables, beef, water, and salads that have been fecally contaminated.  Treatment with supportive measures is usually adequate and antibiotics are rarely used as most strains are resistant to common, broad-spectrum antibiotics.

Giardia lamblia: Giardia is one of the most common parasites in the United States.  It infects via fecally contaminated food and water.  Both wild and domesticated animals serve as reservoirs for the parasite, providing constant sources of the protozoa.  After infection, it can take on average 7-10 days for symptoms to set in.  Common symptoms include diarrhea, abdominal cramps, fatty or greasy stools, and bloating.  These symptoms can persist for 1-3 weeks.  Giardia is diagnosed by examination of a stool sample or blood test, and can be treated chemically.

Hepatitis A virus – One of the few viruses to cause foodborne illness, Hepatitis A infects via fecally contaminated food or water, as well as filter-feeding shellfish grown in contaminated waters.  The virus’ incubation period averages 25 days but can range from 15-30 days.  Symptoms of infection include nausea, diarrhea, fever, jaundice, and anorexia.  A vaccine is available, as well as an immunoglobulin shot that will prevent disease post-exposure.  Infections can also clear with only supportive intervention.

Listeria monocytogenes:  Listeria bacteria can survive and thrive in low temperature and low oxygen environments, making them a dangerous foodborne pathogen.  Refrigeration and even freezing does not significantly slow Listeria growth.  It is commonly found in deli meats, soft cheeses, ice cream, milk, and frozen products.  Symptoms present around 3 weeks after exposure and include diarrhea, abdominal pain, headache, and fever.  If the infection spreads to the nervous system, other symptoms include headache, stiff neck, confusion, balance problems and convulsions.  Pregnant women are especially vulnerable to infection, and the infection can cause premature birth of a likely Listeria-infected baby, still birth, and miscarriage.   For this reason, antibiotics are often given to infected pregnant women and infants of mothers who were infected.

Noroviruses:  Formerly known as “Norwalk” or “Norwalk-like” viruses, Noroviruses cause extreme gastrointestinal distress.  They spread easily from person-to-person via contaminated surfaces and food once an outbreak has begun.  Symptoms include nausea, projectile vomiting, diarrhea, abdominal cramps, body aches, headache, and fatigue lasting for 24 to 72 hours.  The incubation period is between 10-96 hours.  Medical professionals diagnose Norovirus infection by analyzing stool samples or environmental swabs.  Supportive treatment through the replacement of fluids is administered as needed.

Salmonella spp. (non-typhoidal) – Salmonella bacteria are commonly found in poultry, eggs and egg products, meat, unpasteurized milk, and pre-cut melons. Many different serotypes of Salmonella exist but share the same symptoms–diarrhea, abdominal cramps, fever, headache and vomiting, which appear from 12 to 72 hours after exposure and last for about one week.  Salmonellosis is diagnosed through laboratory analysis of stool samples.  Treatment has become increasingly difficult as many strains are now resistant to common antibiotics, but antibiotic treatment remains the common means of decreasing the duration of salmonellosis.  Even with treatment, a post-infection complication called Reiter’s syndrome can cause pain in joints, eye irritation and painful urination.  These problems can persist for years and can lead to chronic arthritis.

Salmonella Typhi (Typhoid Fever):  A serotype of Salmonella, typhoid fever causes a rather different disease than the other types.  Untreated typhoid fever has three stages with different symptoms, ranging from a slowly progressing fever that reaches 104ºF, malaise, headache, cough, a rash, enlarged liver and spleen, and nosebleeds, to delirium, intestinal hemorrhage, intestinal perforation, sepsis, and death.  Other symptoms include green diarrhea or constipation, and in the final stages the bacteria can infect the brain, heart and bones.  Typhoid fever can be treated effectively with antibiotic drug.  Onset of the first phase can occur between 3 days and 3 months after exposure, and infected persons can be asymptomatic carriers.  Asymptomatic carriers can still spread the disease to others.

Shigella spp.:  Shigella is an extremely contagious bacterial infection.  Contamination of food and water by fecal matter leads to ingestion of the bacteria, which cause gastrointestinal issues including diarrhea, fever, nausea, vomiting, severe abdominal cramping, and tenesmus, plus straining during bowel movements.  Symptoms of infection begin 1-3 days after exposure and last about a week.  However, a return to normal bowel function may take months, and around 2 percent of patients develop post-infection arthritis.  Shigellosis can be treated with antibiotics after diagnosis through analysis of a stool sample.  Importantly, certain anti-diarrheal medicines can make the illness worse and should be avoided.

Staphylococcus aureus: Staph is better known as a hospital-associated infection of wounds rather than as a foodborne illness.  Ingested Staph bacteria produce heat-stabile enterotoxin that induces nausea, vomiting, diarrhea, and abdominal cramps within 2-4 hours. These symptoms usually abate after a day.  Staph is usually found in ham, meat and poultry, cream filled pastries, custard, unpasteurized milk and milk products, and high protein leftover foods.  Staphylococcal food poisoning is diagnosed by identifying toxins in stool, vomit, or food items in outbreaks and by symptoms for isolated cases.  Patients are given fluids and told to rest.  Because the illness is due to a toxin, not bacteria, patients are not treated with antibiotics.

Trichinella spiralis:  Trichanosis is caused by the parasitic roundworm Trichinella spiralis found in undercooked pork, bear, wild feline, fox, dog, wolf, horse, walrus, and seal meat.  Initial symptoms of infection include diarrhea, nausea, vomiting, and abdominal discomfort.  This is followed by muscle aches, swelling of the eyelids, fever, chills, cough, itchy skin, and, in the case of heavy infection, problems with muscle coordination and cardiopulmonary problems.  Occasionally, life-threatening complications arise when the heart, lungs and nervous system are affected by the cysts.  The severity and type of symptoms depend on the number of larva ingested.  The ingested cysts-containing larvae enter the stomach where the cyst covering is dissolved, releasing the worm into the intestine where it matures and mates. Females lay eggs that travel in the bloodstream to the muscles, where they form cysts.  The first symptoms appear 8-15 days after consumption of infected meat.  Trichinosis is diagnosed through blood tests and muscle biopsy.  Treatment with anti-helminth drugs clears the infection.

Vibrio cholera 01 or 0139:  Cholera epidemics still plague the world’s population.  This bacterial infection of the intestine causes sudden, profuse, watery, “rice-water” diarrhea accompanied by debilitating cramps and vomiting and leading to rapid dehydration.  Untreated, cholera’s dehydrating effect can cause death in hours.  It is spread via fecally contaminated water during an outbreak, but the bacteria are also found in shellfish that dwell in brackish water.  Symptoms can begin as shortly as a few hours after exposure, but can start as late as 5 days afterward.  Treatment with oral rehydration fluid remains the best way to treat cholera, though antibiotics can be prescribed in some cases.  The rehydration mixture of salts, sugars and water resupplies fluids and electrolytes lost in the diarrhea and vomiting.  A vaccine is available outside the U.S. by a Swedish company, but is not recommended to U.S. travelers.

Vibrio parahaemolyticus:  A relatively newly discovered pathogen, V. parahaemolyticus,z infects marine fish, shellfish and crustaceans, both raw and cooked.  The bacteria causes  watery diarrhea, abdominal cramps, nausea, vomiting, fever, and headache.  These occur within 12-24 hours of consumption of tainted seafood and last for 3 days.  The illness is usually self-limited and does not require treatment beyond rehydration.  In cases of severe or prolonged symptoms, a broad spectrum antibiotic may be prescribed.

Vibrio vulnificus:  Found mostly in raw oysters, V. vulnificus bacteria cause fever, nausea, abdominal cramps, and muscle aches within a day or two of eating the contaminated shellfish.  This infection can be especially dangerous to the immunocompromised, particularly those with liver disease, who can develop septicemia with a mortality rate of 50 percent.   V. vulnificus infections are diagnosed through stool or blood cultures.  Early treatment with antibiotics reduces the mortality rate and prevents the infection from spreading to the blood.

Yersinia enterocolitica:  This bacterial infection leads to diarrhea, vomiting, abdominal cramps, fever and headache.  In adults, abdominal pain may be centered on the right side, leading to a misdiagnosis as appendicitis.  It is caused by eating contaminated foods, commonly chocolate milk, tofu, water, and undercooked pork such as chitterlings.  Infants can be infected by caregivers who handle raw pork.  Symptoms begin around 3-7 days after exposure and can last up to 3 weeks.  Stool sample analysis provides a diagnosis, but, as most laboratories do not include tests for Yersinia bacteria in their standard tests, this must be ordered specifically.  Normally, Yersinia infections resolve on their own, but in cases of severe infections a wide range of antibiotics may be prescribed.  Long-term consequences of infection are rare, but include joint pain in the ankles, knees and/or wrists and a rash, called “erythema nosdosum,” on the legs and trunk.  They resolve in 1 to 6 months and 1 month, respectively.

Heavy metals:  Overdoses of heavy metals, such as arsenic, cadmium, copper, mercury, zinc and lead, can occur by consuming highly acidic foods stored or prepared in containers lined or contaminated with the metal.  This type of food poisoning causes nausea, vomiting, diarrhea and abdominal cramps within minutes of eating the offending foods.

Ciguatoxin:  This toxin forms in fish that have eaten dinoflagellates, a single-celled organism.  When the fish is consumed the toxin causes initial gastrointestinal symptoms of vomiting, diarrhea, and cramping, followed by neurological manifestations.  The neurological symptoms include burning or prickling at the lips, tongue, and extremities as well as alternating sensations of hot and cold, hallucination, and nightmares.  Predatory reef fish such as barracuda, snapper, grouper and amberjack caught in the South Pacific and the Caribbean commonly contain ciguatoxin.  The symptoms of Ciguatoxin start within 2-8 hours of ingestion and the neurologic ones can last several months. In severe cases, treatment with the drug Mannitol can has been shown to help.

Paralytic Shellfish Poisoning (PSP):  This type of poisoning occurs after consuming filter-feeding shellfish, usually from the colder, coastal waters of the Pacific Northwest or New England, that have contaminated “red tide” toxins in their diet.   When ingested, the toxins cause neurological symptoms, beginning with numbness and tingling in  the lips and mouth that  spreads to adjoining parts of the face and, sometimes, other parts of the body.  It can be fatal in severe cases where the respiratory system becomes paralyzed.  Symptoms vary depending on the amount of toxin ingested and can begin from 30 minutes and 3 hours after eating the shellfish.

Monosodium Glutamate (MSG) poisoning:  Large amounts of MSG (usually greater than 1.5 grams) can lead to physiological symptoms.  These include a burning sensation in the chest, neck abdomen or extremities, sensations of lightness and pressure over the face, or a heavy feeling in the face.  These symptoms start within minutes of consumption.

Cyclopeptides Mushroom Poisoning:  The most common form of mushroom poisoning is from the Aminita phalloides mushroom.  The α-amatoxin found in this genus binds to RNA polymerase II, making it impossible for cells to synthesize proteins leading to cell death.  The early symptoms of nausea, vomiting, and diarrhea present within a day, but usually abate on their own.  However,after this the toxin affects the liver cells and continues to destroy them.  If not treated, liver failure and death are likely to occur.  There is no antidote to α-amatoxin so treatment consists of replacing fluids and electrolytes, stomac
h pumping, and consuming activated charcoal.  Dialysis and profusion of the blood in the first 24 hours may be effective in removing the toxin already in the blood.  If fulminant liver failure occurs, the only treatment option is a liver transplant.

Muscarinic Mushroom Poisoning: Many species of mushrooms in the genus’ Inocybe and Clitocybe contain muscarine, a substance that stimulates the parasympathetic nervous system causing sweating, shortness of breath, salivation, diarrhea, pupil constriction, low blood-pressure and a slow heartbeat.  These symptoms occur within 1 hour of ingestion and last 4 to 24 hours.  Most cases resolve on their own, but atropine can be given in severe cases.

Scrombroid fish poisoning:  Scrombroid poisoning is caused by a histamine-like substance that develops in dead fish that have not been kept at safe temperatures as bacteria break down the tissues.  Common fish sources include tunas, bluefish and mackerel.  The histamine-like substance causes diarrhea, headache, nausea, vomiting, and flushing, as well as a peppery taste in one’s mouth.  These reactions occur within 1 hour of eating the fish.  Treatment with anti-histamines and epinephrine can be necessary in serious cases.

Neurotoxic Shellfish Poisoning (NSP):  Caused by a dinoflagellate found in coastal Gulf of Mexico and Atlantic Seaboard waters, this toxin is ingested by humans via shellfish such as oysters, clams and mussels.  The NSP toxin causes numbing in the mouth and face, coordination problems, nausea, vomiting, diarrhea and a reversal of hot/cold sensations.  These symptoms usually last 2-3 days.

Amnesiac Shellfish Poisoning (ASP):  A microscopic, aquatic plant, or diatom, called Nitchia pungens causes this type of shellfish poisoning.  Gastrointestinal symptoms begin within 24 hours of ingestion.  Other symptoms include headache, dizziness, short-term memory loss; severe cases can result in seizures, focal weakness, paralysis and death.  Short-term memory loss can be permanent.  There is no treatment for ASP.