Sudden, Awful Intestinal Distress--Is it the Flu or a Foodborne Illness--or Both?

flu"Was it a bug or something I ate?" victims often wonder as they run repeatedly to the bathroom. But this is not really an either/or matter. There's a lot of overlapping of these categories. What we commonly call "stomach flu" is usually caused by the norovirus. This winter season, there's a particularly nasty strain of it spreading rapidly throughout the country.  It's easily contracted, says the Centers for Disease Control and Prevention (the CDC) from an infected person, food or water, or even contaminated objects.  It can come from a friend's sneeze (or kiss), salad, or, often, a public washroom doorknob.  But this highly contagious condition is different from the intestinal discomfort caused by eating food that has become contaminated due to mishandling.  The latter is not contagious, not transferable from person to person.


How common are these conditions in the U.S.?  Very.  About 1 out of 6 Americans suffers from short-term gastrointestinal misery every year.  Norovirus, the leading cause of foodborne disease outbreaks, accounts for some 20 million cases a year and about 800 deaths, the CDC reports.  Most fatal cases occur among the very young, the very old, and those with weakened immune systems.




The commonly-used phrase “stomach flu” (which doctors call gastroenteritis) is an irritation and inflammation of the stomach and intestines (the gastrointestinal tract) usually attributed to a virus. It isn’t really a flu; it should not be confused with the seasonal respiratory influenza virus that much of the population gets vaccinated against. There is no vaccine for viral gastroenteritis. It’s highly contagious and almost impossible to escape if you’re near someone who has it.  More than 50% of cases are spread by contaminated food, usually the result of someone who is carrying the norovirus (whether having symptoms or not) handling the food without washing his/her hands. Many other viruses can also cause intestinal distress, but the norovirus is the most common, partly because it's the hardiest. It can survive on surfaces for weeks; people who are carriers can pass it on to others for awhile even before they have symptoms and even after they've recovered.   


On the other hand, the term "foodborne illness" is commonly used to refer to a non-contagious condition that comes only from contaminated food or water.  It is commonly caused by bacteria. Food scientists and public health officials prefer the term “food-borne illness” to the older term “food poisoning” because this illness is not caused by chemical or natural toxins but by one of these: bacteria or toxins produced by a pathogen, virus, or parasite.  For the sake of clarity and custom, this article will refer to contagious gastroenteritis as "stomach flu" (or norovirus) and the non-contagious form as "foodborne illness."






It's impossible to protect yourself from the norovirus because it's so easily transmitted in many different ways. At present, there is no vaccine to protect people from this virus, but scientists are working on a nasal spray that may be available in 5-10 years. The Handwashing for Life Institute claims that alcohol-based hand sanitizers kill noroviruses (some brands better than others), the CDC disagrees.  Sanitizers may be effective against some strains of flu, but not against norovirus, the CDC says.  Soap and water works much better.  CDC research found that institutional facilities using the sanitizers rather than soap and water were six times more likely to have norovirus outbreaks. Serious and frequent hand washing--both sides of the hands with warm water for 20-30 seconds with a lot of soap even under the nails--is what's recommended to give people some protection.  Bleach would be more effective but also hard on the hands. 


Cooking foods kills the norovirus, so the biggest food risk is from produce eaten raw.


According to the CDC, more than 80% of norovirus outbreaks occur between November and April, so now is the time to be vigorous about washing your hands and produce. 


Foodborne illness:


The risk of contracting a foodborne illness can be greatly reduced by proper handling of the edibles you bring into your kitchen. That means always handling food with clean hands; keeping utensils, kitchen surfaces (including storage areas and the refrigerator), and sponges clean and sanitized; washing produce well; avoiding cross-contamination from, for example, raw meat or poultry to fruits to be eaten raw; keeping perishables properly refrigerated; and cooking raw foods to the proper temperature. These behaviors will help considerably to protect you and those who eat at your table.


It’s more difficult to protect yourself against food served to you away from home. Often, you can’t recognize food that will make you sick because the bacteria that cause illness are sneaky—they usually don’t exhibit hostile signs such as bad smell or appearance. Ironically, foods that do exhibit these signs of spoilage usually don’t cause illness, especially if they're discarded promptly.


The number of non-contagious foodborne illnesses tends to rise during the summer when people are eating food outdoors more and traveling with food, which leads to temperature abuse and other sources of contamination.


Symptoms and Responses


Foodborne illness and stomach flu have similar symptoms-- diarrhea, abdominal cramps, nausea, headache, vomiting, fatigue, weakness, and perhaps dehydration and fever.  All this discomfort is caused by inflammation of the stomach and intestines.  Fortunately, in most cases, the symptoms disappear within 1-3 days without medical intervention. Therefore, you may conclude that you don’t need to know the cause to respond appropriately. However, there are some benefits in figuring out which condition you have or had. If you have a stomach flu, you should stay home and out of contact with friends and co-workers so that you don’t make them sick, too. If you have a foodborne illness you are not contagious, so you don’t need to try to shield others from your germs.  If your symptoms can be traced to a particular source, you should report this information to the place where you purchased or ate the product, your local health officials, and the FDA.  


Speaking on CNN recently, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID) pointed out that, when gastroenteritis hits, serious dehydration is the problem that usually causes patients to wind up in the hospital.  His advice to patients: stay as well hydrated as you can, not just by drinking water but by consuming water with electrolytes (beverages such as Gatorade or Powerade). 


Finding the Cause


Many times victims never figure out the cause of their gastrointestinal distress.  However, if you’re a good detective, you may conclude that it’s probably stomach flu if others became sick several hours or a day or so after contact with you, and there was no food involved in the contact.  On the other hand, if, among people that ate the same food as you did, some or most got sick, but those that didn’t share your food choices remained well, you can probably assume the symptoms were caused by tainted food. Sometimes it takes a day or two to assess this information. In some cases, only a medical test can provide the indisputably correct answer as to what caused the symptoms.


These are the steps necessary for a foodborne illness to develop, according to University of Georgia food scientists:


1. The microorganism or its toxin must be in [or on] the food.


2. The food must be suitable for the organism’s growth. [That could mean enough moisture and a not too acidic environment.]


3. The temperature must be suitable for the organism’s growth. [That’s why it’s important to keep perishables out of the “danger zone,” 40°F-140°F.]


4. Sufficient time must elapse for the number of pathogens to increase. [This time is a lot shorter than many people realize; pathogens can sometimes double in number within a few minutes. The higher the temperature in the danger zone, the faster tis doubling will occur, says food scientist Dr. Joe Regenstein.]


5. At the time it's eaten, there must be enough microorganisms (or their toxin) present in the food to cause illness.


6. You must eat the food.


If you think your distress was caused by food contaminated by mishandling, you should review how you (or someone else assisting in your kitchen) handled the food you ate shortly before you got sick.  Perhaps you’ll detect a mistake and learn how to make your kitchen safer.  However, just because you (and/or others at your table) got sick after eating your home-cooked meal, this doesn’t prove you did something wrong.  Food can get contaminated anywhere along the food chain, in some cases by pathogens that home procedures cannot kill.


Scientists divide foodborne illnesses into these two categories: food infection and food intoxication.  Food infection is caused by eating food containing live bacteria that continue to increase in number to the point where they cause illness. Salmonella (of which there are more than 1200 types) is a well-known example of a food infection. Food intoxication is caused by food that contains a toxin or poison. The bacteria that produced and excreted the toxic waste products may have been killed by cooking, but the toxins may have survived and can still cause digestive upset. Staphylococcus aureus (commonly called “staph”) is an example of a food intoxication. 


One very dangerous, though rare, type of food intoxication is botulism, which is fatal in 60% of cases.  About l10-120 cases occur annually in the U.S., usually caused by food that has been improperly home-canned.  Commercially canned foods have an extremely safe record.  According to University of Georgia food scientists, more than 17 million cans of food are commercially prepared and sold in the U.S. annually, and, since 1925, they have caused only 3 botulism outbreaks resulting in 4 deaths.  Botulism spores can survive in boiling water, but heating food to a typical cooing temperature of 176°F for 10-20 minutes (depending upon the food) will greatly reduce the risk of illness. 


Shelf Life Advice contains a great deal of information about foodborne illness and the pathogens that cause it. Here are some relevant links: 




Joe Regenstein, Ph.D., Cornell University, Dept. of Food Science  "Surveillance for Norovirus Outbreaks"  "Nasty, contagious norovirus is 'everywhere' now"  "CDC Report finds Norovirus Outbreak in US Has Taken A Stranglehold, Cases Rising"  "Hand Sanitizers Offer Weak Defence Against Norovirus" "Alcohol Hand Sanitizers Do Kill Norovirus, responds HandWashing for Life Institute" The University of  Georgia College of Agricultural & Environmental Sciences Cooperative Extension Service “Preventing Food Poisoning and Food Infection” “Seasonal Influenza: The Disease” “Food Poisoning Vs. Stomach Flu" “Cold and Flu: What is the Stomach Flu?" “Foodborne illness”


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