Food poisoning is a common, yet distressing and sometimes life-threatening problem for millions of people throughout the world. People infected with foodborne organisms may be symptom-free or may have symptoms ranging from mild intestinal discomfort to severe dehydration and bloody diarrhea. Depending on the type of infection, people can even die as a result of food poisoning.
More than 250 different diseases can cause food poisoning. Food poisoning is an illness caused by eating contaminated food. Most people get better without the need for treatment.
Symptoms: The common initial symptoms ar feeling sick, vomiting, diarrhoea and stomach cramps.
Common foods: Foods particularly susceptible to contamination if not handled, stored or cooked properly include: raw meat and poultry, raw eggs, raw shellfish, unpasteurised milk, ‘ready to eat’ foods, such as cooked sliced meats, pâté, soft cheeses and pre-packed sandwiches.
Method of contamination: Food can become contaminated at any stage during production, processing or cooking: not cooking food thoroughly (particularly poultry, pork, burgers, sausages and kebabs), not storing food that needs to be chilled at below 5°C correctly, leaving cooked food for too long at warm temperatures, someone who is ill or who has dirty hands touching the food, occasionally by eating food that has passed its ‘use by’ date, and cross-contamination (the spread of bacteria, such as E. coli, from contaminated foods).
General treatment: Most people with food poisoning get better without the need for treatment. To help relieve your symptoms you should rest and drink plenty of fluids. It is best to avoid food until you feel much better. When you start eating again, choose foods that are easily digested, such as toast.
Prevention of dehydration: It’s important that you do not become dehydrated because it will make you feel worse and lengthen your recovery. Try to drink as much water as you can, even if you can only sip it, particularly every time you pass diarrhoea. Soda pop such as Pepsi or ginger ale are often satisfactory replacement fluids.
Oral rehydration salts (ORSs) are recommended for people vulnerable to the effects of dehydration, such as the elderly and those with another health condition. ORSs help replace salt, glucose and other important minerals lost through dehydration. They are available in sachets from pharmacies and you dissolve them in water to drink.
When to see a doctor: your symptoms are severe and do not improve after a few days, you have a high temperature (fever) of 38°C (100.4°F) or over, you have symptoms of severe dehydration, such as sunken eyes and passing small quantities of dark, strong smelling urine
there has been an outbreak of similar cases of food poisoning linked to a possible source of contamination, or if you have a baby with food poisoning.
Occasionally, food poisoning can have more serious effects on a person’s health, particularly if they are vulnerable to infection. For example, if you are over 65 years of age, or you have a condition that weakens your immune system, such as HIV or cancer, your risk of developing more serious symptoms is increased. Babies are also at increased risk.
Signs that you may have a more serious case of food poisoning that requires medical attention include: vomiting that lasts for more than two days, not being able to keep liquids down for more than a day, diarrhoea that lasts for more than three days or is bloody, or fever.
Anitnauseants. To control vomiting when you are feeling dry, try the following drugs.
Gravol. Available as tablets, rectal suppositories or by injection from a doctor. The suppositories can be particularly helpful. 100mg suppositories are best for adults and pediatric suppositories are available.
Stemetil. This is much more potent than gravol. Dosing must also be more careful because of side effects, so follow the instructions. It is available as tablets, sublingual tablets (under your tongue), suppositories or by injection. It is available over the counter in many third world countries, but is prescription in first world countries.
Diarrhea control. Drugs such as Imodium or Lomotil are best avoided unless you must travel and getting to a toilet might be a problem. They may prolong symptoms. Letting the diarrhea run its course may allow you to excrete the organism more effectively.
VIRAL INFECTIONS
1. Norovirus
Norovirus is a small virus that is highly contagious between humans. The many strains of noroviruses cause a self-limited gastrointestinal illness that many refer to as the “stomach flu.” This teminology causes confusion as there is no relationship between this and influenza, which has no gut symptoms but is a pure respiratory illness with symptoms of a cold followed by a usually dry cough. Influenza outbreaks commonly occur in the winter, the type of influenza changes on a yearly basis, and it can be prevented with vaccination.
Many people may not be familiar with the term norovirus, but it’s actually a relatively new term for an old disease. There are many different types of norovirus. Originally, strains were named based on the city in which they were first identified. Thus, one common strain used to be called Norwalk virus. Based on genetic typing, we now know that there are at least 25 different strains of norovirus that affect humans. It is a common problem with travelers with outbreaks of norovirus infection common on cruise ships but outbreaks have also been documented as coming from restaurants, schools, and nursing homes.
Noroviruses are the most common cause of gastroenteritis in first world countries. According to statistics from the CDC, there are 21 million cases of norovirus infection annually in the U.S., of which one-quarter are related to food-borne outbreaks. Outbreaks occur throughout the year but are more common in the winter months. Outbreaks can occur almost anywhere in the world. In 2012, a new strain named GII.4 Sydney was identified. Since the first outbreak, the virus was quickly detected in New Zealand, France, and the U.S. It has caused about half of the norovirus infections detected in 2012-2013 in the U.S. A new outbreak of norovirus occurred at Yellowstone National Park, causing illness in about 200 visitors and camp employees in June 2013. In January, 2014, 600/3,000 passengers on a Royal Caribbean International cruise ship became ill with norovirus. In January, 2014, 600/3,000 passengers on a Royal Caribbean International cruise ship became ill with norovirus.
People acquire the virus by ingesting material contaminated with small amounts of infected feces or fluids. Food and water may be contaminated during processing or handling.
Symptoms. Most people get sick within one day of ingesting norovirus (range 12-48 hours) so the virus has a short incubation period. People may be contagious during this period. All people are contagious while they are having symptoms. Although the most contagious period is over when the patient’s symptoms resolve, even some people who appear to have recovered completely after a norovirus infection may continue to shed the virus for weeks in their stool and may be a source of infection to others.
Symptoms and signs include vomiting or watery diarrhea or both. Fever occurs in one-third to one-half of infected people. Cramping abdominal or stomach pain and a general feeling of tiredness, headache, and muscle aches are common. People are usually thirsty, although they may have trouble keeping fluids down. In general, patients who can orally ingest about the same amount of fluid they lose through diarrhea, vomiting, or both do well. Symptoms in adults may be different than symptoms in children. Young children and babies may not complain of thirst but may appear listless or lethargic as they become dehydrated. Symptoms may be more severe in debilitated, elderly patients or pregnant patients. People who are unable to replace their fluids and develop signs of dehydration need medical care.
Most people have a mild illness that lasts two to three days. In contrast to bacterial diarrheas, such as those caused by Shigella or Campylobacter bacteria, norovirus does not cause blood or pus in the stool. The length of infection may be prolonged in patients who are in the hospital or in young children.
There is a short lag or incubation period (up to two days) between the time that people acquire the virus and the time they get symptoms. Treatment. There is no specific treatment for norovirus, but it is important that infected people stay well hydrated. Fluids containing sugar and electrolytes should be encouraged. Intravenous fluids may be needed if the person cannot maintain an adequate oral intake of fluids.
Diagnosis. Because the symptoms of norovirus are similar to those of other common viral diarrheas like rotavirus, it is necessary to do specific tests to identify the virus. Once norovirus has been confirmed in an outbreak setting, it is not necessary to test every person. Rather, people with typical symptoms are assumed to have acquired the virus.
Complications are usually related to the degree of dehydration. Young children and the elderly are at special risk for dehydration.
Treatment. There is no specific treatment or medication for norovirus. It is important that infected individuals remain well hydrated, drinking plenty of fluids. Fluids containing electrolytes and sugars should be encouraged. Over-the-counter antidiarrheal medications may be used according to directions but should be avoided in cases with severe abdominal pain or fever. Some researchers advise people to avoid these medications if possible as they may prolong the disease.
Prevention. Because the disease is highly contagious, it is important for caretakers to clean their hands whenever they come into contact with the ill person or their environment. This is much harder than it sounds. One sick crew member on a cruise ship can contaminate food served to hundreds of people. Contamination while picking fresh vegetables or fruit can lead to widespread outbreaks as the product is sold across the country.
The risk of food-borne outbreaks or outbreaks within hospitals or nursing homes may be minimized by following established standards that include hand hygiene.
Unfortunately, people who get norovirus do not have immunity against future infections. Although the body makes antibodies against the infecting strain, there are many strains that cause infection. The virus constantly creates small mutations in its RNA to make new strains that evade the human immune system. Because there are many different strains of norovirus, it has been difficult to make a vaccine and there is no commercial vaccine currently available.
2. Rotavirus
Rotavirus is the most common cause of severe diarrhea among infants and children throughout the world and causes the death of about 500,000 children worldwide annually.Most unvaccinated children become infected with rotavirus by age 3. Adults sometimes become infected, but the resulting illness is usually mild. There are different strains of rotavirus, and multiple infections by different strains may occur.
Symtpoms. Rotavirus causes fever, vomiting, and watery diarrhea. Rotavirus infection is highly contagious. Rotavirus illness typically resolves on its own after three to nine days.
Vaccines to prevent rotavirus infection are available.
BACTERIAL INFECTIONS
Symptoms of these types of food poisoning usually begin 1–3 days after eating contaminated food. They cause an actual infection in your intestines and is due to bacteria such as salmonella or Escherichia coli (E. coli O157:H7), Campylobacteror, Shigella, E. coli , Listeria, or botulism .
1. Campylobacter
Campylobacter is a bacterium that causes acute diarrhea. Transmission usually occurs through ingestion of contaminated food, water, or unpasteurized milk, or through contact with infected infants, pets, or wild animals.
Symptoms of campylobacter include: diarrhea (sometimes bloody), nausea and vomiting, abdominal pain and/or cramping, malaise (general uneasiness), fever
Campylobacter infection can be serious, especially in those with weakened immune systems. In rare cases, campylobacter infection can cause additional problems such as arthritis or brain and nerve problems. Occasionally, these problems occur after the diarrhea has stopped.
Diagnosis: If you think you may have been exposed to campylobacter infection, see your doctor. By testing a sample of stool, the bacteria can be identified.
Treatment: If you are found to have the infection, you will likely recover on your own without treatment within two to five days. Drink plenty of fluids to prevent becoming dehydrated. In more severe cases, antibiotics (such as Cipro), if given early in the illness, can be used to shorten the length of time you are sick.
2. Salmonella
Salmonella is a bacterial infection that can be passed on to humans from domestic and wild animals, including poultry, pigs, cattle, and pets. But most often, it is caused by drinking unpasteurized milk or by eating undercooked poultry and poultry products such as eggs. Any food prepared on surfaces contaminated by raw chicken or turkey can also become tainted with salmonella. Less often, the illness may stem from food contaminated by a food worker.
Salmonella can escape from the intestine and go into the blood and travel to other organs. It may become a chronic infection in some people, who can be symptom-free yet capable of spreading the disease to others. Salmonella infections occur worldwide, but it is most extensively reported in North America and Europe.
Symptoms: Acute onset of fever, abdominal pain, diarrhea, nausea, and vomiting (sometimes). These symptoms, along with loss of appetite, can persist for several days.
Although most people recover completely (which sometimes can take several months), salmonella infection may cause a condition known as Reiter’s syndrome in a small percentage of people. Symptoms of Reiter’s syndrome include joint pain, eye irritation, and pain when urinating. The joint pain of Reiter’s syndrome may develop into chronic arthritis.
Salmonella infection rarely causes death, although it can occur in the very young, very old, or among those who have compromised immune systems.
Prevention. To prevent salmonella infection, avoid eating raw or undercooked meat or poultry products, including eggs. It is also important to avoid “cross-contamination” which can occur if food is being prepared using the same utensils, or on the same surfaces, as those used for raw or undercooked meats or poultry products.
Wash hands frequently during and after food preparation. Those with a salmonella infection should not be involved in food preparation. Wash hands with soap after handling reptiles, birds, or after contact with pet feces. Avoid contact between reptiles (turtles, iguanas, other lizards, and snakes) and infants or people with weakened immune systems.
3. Shigella
Shigella is a bacteria generally transmitted through feces. It causes dysentery, an infection of the intestines causing severe diarrhea. The disease generally occurs in tropical or temperate climates, especially under conditions of crowding, where personal hygiene is poor.
Symptoms: bloody diarrhea, fever, nausea, vomiting, cramps.
Diagnosis: If you think you may have been exposed to shigella, see your doctor. By testing a sample of stool, the bacteria can be identified. People with mild infections usually recover within a few days without special treatment. Drinking fluids to prevent dehydration is usually all that is needed. However, with severe infections, antibiotics and more aggressive treatment to prevent dehydration are often needed.
How Can Shigella Infection Be Avoided? The shigella bacteria from stools of infected people can be passed to others if hygiene or hand-washing habits are inadequate. To help prevent transmitting the infection, always wash hands thoroughly after using the bathroom or changing diapers.
4. E. Coli O157:H7
E. coli O157:H7 is a growing cause of foodborne illness. An estimated 73,000 cases of these E. coli infections occur in the U.S. every year, according to the CDC.
Most E. coli O157:H7 infections have been associated with eating undercooked, contaminated ground beef. Drinking unpasteurized milk and swimming in or drinking sewage-contaminated water can also cause infection. Bacteria from stools of infected people can be passed to others if less than adequate hygiene or hand-washing habits are present. Young children often continue to shed the organism in their feces for a week or two after their illness resolves.
In some people, particularly children under the age of 5 and the elderly, the E. coli infection can cause a serious complication called hemolytic uremic syndrome. Hemolytic uremic syndrome causes the destruction of red blood cells and kidney failure. About 2%-7% of infections lead to this complication, according to the CDC.
Diagnosis: If you think you may have been exposed to the E. coli infection, see your doctor. By testing a sample of stool, the bacteria can be identified. It is recommended by the CDC that all those who have sudden, bloody diarrhea get their stool tested for this type of E. coli.
Most people recover on their own within about five to 10 days.
Hemolytic uremic syndrome is a medical emergency and most often will be treated in an intensive care unit.
Prevention: You can prevent E. coli infection by thoroughly cooking ground beef, avoiding unpasteurized milk, and washing hands carefully after handling meat, using the bathroom, or changing diapers.
5. Listeria
Listeria is a bacteria primarily found in soil and water. According to the CDC, vegetables can become contaminated from soil or from manure used as fertilizer. Animals carrying the bacterium can also contaminate food. Listeria has been found in many types of uncooked foods, such as meats and vegetables, as well as in processed foods that become contaminated after processing, such as soft cheeses (like feta and crumbled blue cheese) and cold cuts.
Unpasteurized milk or foods made from unpasteurized milk may also be sources of listeria infection. Listeria is killed by pasteurization, and heating procedures used to prepare ready-to-eat processed meats should be sufficient to kill the bacterium. However, unless good manufacturing practices are followed, contamination can occur even after processing.
According to the CDC, an estimated 2,500 people in the U.S. become seriously ill from a listeria infection each year, and of these, 500 will die. The CDC reports that those at increased risk for developing listeriosis include: Pregnant women, people with weakened immune systems, people with cancer, diabetes, or kidney disease, people with AIDS, people, such as those with asthma, who take steroid medication, and the elderly.
Symptoms: Fever, muscle aches, nausea, and diarrhea. If listeria infection spreads to the nervous system (brain and spinal cord), the following symptoms can occur: headache, stiff neck, confusion, loss of balance, and convulsions.
Infected pregnant women may experience only a mild, flu-like illness; however, infection during pregnancy can lead to premature delivery, infection of the newborn, or even stillbirth. There is no routine screening test to find out if you are likely to contract listeria infection during pregnancy. If you have symptoms of listeriosis, consult your doctor immediately.
Symptoms of E.coli infection can include severe bloody diarrhea and abdominal cramps, but sometimes the infection causes non-bloody diarrhea, a slight fever, or no symptoms at all.
Diagnosis: Listeria infection is often diagnosed by a medical history and confirmed by blood or spinal fluid tests.
Treatment: Antibiotic treatment will usually cure the infection, and when given promptly to an infected pregnant woman, may prevent infection of her fetus. Even with prompt treatment, some infections result in death. In the elderly and people with other serious medical problems, these infections are more likely to be fatal.
6. Botulism
The bacterium Clostridium botulinum is responsible for causing the rare but serious illness botulism.
According to the CDC, the three main types of botulism are foodborne, wound, and infant botulism. Foodborne botulism is caused by eating foods that contain the botulism toxin. Wound botulism, which is very rare, is caused by a toxin produced from a wound infected with C. botulinum. Infant botulism is caused by consuming the spores of botulinum bacteria, which grow in a child’s intestines. All forms of botulism can be deadly and are considered medical emergencies.
Symptoms: blurred vision, double vision, droopy eyelids, slowed or slurred speech, difficulty swallowing, dry mouth, and muscle weakness. In infants with botulism the symptoms include:, poor feeding habits, constipation, weak crying, lethargy, poor muscle tone
If these symptoms are untreated, they may lead to paralysis of the arms, legs, trunk, and respiratory muscles. Symptoms of foodborne botulism usually develop 18 to 36 hours after consuming contaminated food, but symptoms can occur as early as six hours or as late as a week to 10 days.
Diagnoses: A diagnosis of botulism is made by the presence of appropriate symptoms of nerve weakness and by lab tests that detect the toxin or by culture of C. botulinum from the person’s stool.
Treatment: The respiratory failure (inability to breathe) and paralysis that occur with severe botulism may require intensive medical and nursing care in a hospital. If diagnosed in its early stages, foodborne botulism can be treated with an antitoxin medication. Your doctor may also try to remove any contaminated food left in the digestive system by inducing vomiting or by using enemas.
Infants infected with the bacteria require hospitalization and possibly care in an intensive care unit. The botulism antitoxin is not recommended for infants.
Prevention: Although there are very few cases of botulism poisoning each year, prevention is extremely important. According to the CDC, foodborne botulism has often been linked to home-canned foods with a low acid content. These foods include asparagus, green beans, beets, and corn. People have also become infected from other sources including chopped garlic in oil, chili peppers, tomatoes, improperly handled baked potatoes cooked in aluminum foil, and home-canned or fermented fish (such as sardines). Persons who can their own food should follow strict canning procedures to reduce contamination of foods. Honey should not be given to children younger than 12 months of age, as it can contain spores of C. botulinum and is known to cause infant botulism.
How to deal with food poisoning while travelling—and how to avoid it altogether
Some countries have a reputation for putting travellers at a higher risk for gastrointestinal illnesses. But you can get sick from an improperly handled meal anywhere in the world.
Pad thai from a Bangkok street vendor or raw milk cheese from a bistro in France taste delicious in the moment. But for many travelers, the local dishes that make trips meaningful sometimes give them food poisoning—and the wrong sort of vacation memories.By some metrics, gastrointestinal infections related to food or water affect 30 to 70 percent of all travelers during or immediately after their trips, according to a 2015 study in BMJ Clinical Evidence. Each year, one in six Americans and nearly one in 10 people worldwide suffer from such illnesses caused by bacteria (E. coli, salmonella, listeria), viruses (norovirus, hepatitis A), or parasites (giardiasis, roundworms, tapeworms).
Lower-income countries have a reputation for putting travelers at a higher risk for food poisoning, but people are just as likely to be sickened from an improperly handled meal in Italy or Australia—or from some sushi at their local supermarket.
Here’s why people get food poisoning, what to do if it strikes, and how to (maybe) prevent it.
What causes food poisoning?
There are 31 major known pathogens that cause foodborne illnesses, including norovirus, salmonella, E. coli, clostridium perfringens, and campylobacter. Depending on the bacteria, parasite, or virus, symptoms could include a few hours to a week of diarrhea and vomiting, plus stomach cramps, fever, or body aches. The most likely culprits? Raw or undercooked chicken, turkey, or meat; raw milk; raw fruits and vegetables; shellfish; and food stored in unsafe temperatures (e.g. an open-air buffet) or prepared in an unsanitary way.
Or the water might be making you sick. According to the U.S. Centers for Disease Control (CDC), more than 180 countries (including popular destinations the Maldives, Mexico, and the Bahamas), have tap water that is unsafe to drink. This means that brushing your teeth with local tap water or even washing your hands before preparing lunch could lead to illness.
“Giardia parasite is pretty common with contaminated water,” says Cindy Chung, a doctor at Kaiser San Rafael Pediatrics in California. “When a kid comes into my office with sudden diarrhea, I ask, ‘Have you been camping? Did you go to the beach? Have you traveled?’”
What can I do if I get sick?
There’s no quick fix for foodborne illnesses. Most will resolve once the bacteria or toxins have been flushed out through watery diarrhea or vomiting. To combat the discomfort during this unpleasant period, doctors recommend ample fluids to prevent dehydration and over-the-counter painkillers (ibuprofen, naproxen) for stomach cramps.
Since diarrhea and vomiting are your body’s natural immune response to expel toxins, only take anti-diarrhea and anti-nausea medications such as loperamide (Imodium A-D) and bismuth subsalicylate (Pepto-Bismol) if you’re boarding a bus or airplane and won’t have easy bathroom access.
(Should you really buy travel insurance?)
To stay hydrated, Chung recommends Pedialyte or low-sugar Gatorade. “Too much sugar makes you feel worse when you have vomiting and diarrhea,” she says. For severe cases, especially for children or the elderly, consider having a doctor prescribe ondansetron (Zofran), a medicine that slows down vomiting so you can drink more fluids.
You may be able to cancel or reschedule travel if you’re too ill to move. Travel insurance sometimes considers food poisoning a valid reason to make flight changes. “But you can’t go to the doctor the day after your missed flight and get a retroactive diagnosis,” says Michelle Couch-Friedman, an ombudsman columnist for The Points Guy and founder of Consumer Rescue, a consumer advocacy organization.
What to do before a trip
Worried about getting sick on a trip? Consult your general practitioner or a travel clinic for recommendations on medications or vaccinations based on your destination. “We might give you a three-day course of azithromycin (Zithromax) because, with traveling, one of the most common bacteria is E. coli,” says Chung. “But we tell patients not to use it unless their stools have blood.” A doctor may give you a hepatitis A vaccine to prevent illness from contaminated food or water.
To help ward off diarrhea, experts at Mount Sinai recommend taking two Pepto-Bismol tablets, four times a day, before and during your trip. This advice is based on a landmark 1987 study of students traveling to Mexico, which showed that Pepto’s active ingredient, bismuth subsalicylate, reduced the incidence of traveler’s diarrhea by approximately 60 percent.
“Generally, E. coli is the most common cause for traveler’s diarrhea, and the medication may help prevent the bacteria from taking hold and [you] developing any symptoms,” says Michael Bolaris, chair of pediatrics and chief of infectious disease at Rancho Los Amigos National Rehabilitation Center in Downey, California. Bolaris cautions that taking bismuth subsalicylate might temporarily give travelers harmless black stools or tongues.
Pack electrolyte powders, water purification tablets, filtered water bottles, and hand sanitizer as well as anti-diarrhea, anti-nausea, and anti-inflammatory medications. Keep supplies in your carry-on, in case of mid-flight sickness or lost luggage.
Remember that the water in airplane bathrooms isn’t potable. “You may actually be introducing yucky microbes by washing your hands prior to a meal or brushing your teeth,” says Couch-Friedman. “Bring a bottle of spring water into the bathroom to brush your teeth, and use hand sanitizer. Otherwise, you could fast-track yourself to gastrointestinal problems.”
What to do during a trip
Find out if the tap water is safe to drink in your destination with the CDC’s Traveler’s Health tool. Many hotels in places with unsafe water have their own filtration systems or provide bottled water. But nasties may come from that iced water at a street market or berries at a roadside food stand. When in doubt, avoid ice, and drink bottled water.
Concerned about single-use plastics? Bring a heavy-duty filtered water bottle (such as Grayl) and fill it with boiled water (if the hotel has a kettle) or water treated with purification tablets (Globaline, Potable-Aqua).
Sometimes, food poisoning happens because travelers have never encountered common bacteria and viruses at their destination. “Locals build up some level of tolerance because their immune systems have been exposed multiple times,” says Bolaris.
That doesn’t mean you have to forgo street food in Southeast Asia or taco stands in Mexico City. Bolaris’ rule? If you can’t clean it or peel it, don’t eat it. Chung advises travelers to watch how vendors prep food. “Are they using utensils, gloves, or bare hands?” When in doubt, stick to piping hot dishes—grilled meats or fried fritters—and shun raw seafood and lukewarm stews.
Help might be coming
A few companies are developing a vaccine against norovirus, which infects 700 million people a year worldwide. The U.S. Food and Drug Administration is launching new Food Traceability Rules in 2026, designed to reduce foodborne illness and deaths by making it easier to trace contaminated foods—cheeses, fruits, vegetables, and seafood—throughout the supply chain.
