Food Poisoning

Food Poisoning

The symptoms of food poisoning can develop rapidly when the stomach itself is affected, or more slowly, even over days or weeks when the effect is more systemic. The most common symptoms are nausea, vomiting, diarrhea, and abdominal cramping. Many cases of food poisoning runs their courses in 24–48 hours, but some can be more serious, even life-threatening.

Viral Causes

Viruses account for most food poisoning cases. Here are the most common viral causes of food poisoning. The Norwalk virus is trasnmitted from person to person as well as from water, shellfish, and vegetables contaminated by feces. It is the most common viral cause of adult food poisoning. Rotavirus is the most common cause of food poisoning in infants and children. It is transmitted from person to person by fecal contamination of food and in the case of children through shared play areas. Hepatitis A (“Hep A”) causes a mild illness with jaundice (yellowing of the eyes and skin). It is transmitted from person to person by fecal contamination of food and it can also be transmitted by blood exchange with, for example, use of contaminated needles.

Bacterial Causes

Bacteria can cause food poisoning by two different ways. Some bacteria infect the intestines causing inflammation and problems with normal absorption of food and accumulation of water. This leads to diarrhea. Other bacteria produce toxins that are poisonous to the human digestive system. When ingested, these chemicals can lead to nausea and vomiting, kidney failure, and even death. Campylobacter is the world’s most most commonly identified food–borne bacterial infection. It is transmitted by water contaminated by animal feces raw poultry, and raw milk. Salmonellae is often referred to as salmonelosis. Salmonellae may recur in a few weeks later as arthritic joint pains. In people with impaired immune systems, Salmonellae can cause a life–threatening illness and is transmitted through undercooked foods such as eggs, seafood, dairy products, and poultry. Staphylococcus aureus is transmitted in foods such as cream–filled cakes and pies, salads (potato, macaroni, egg, and tuna salads, for example) and dairy products. Contaminated potato salad at a picnic is a classic and occurs when the food is not chilled properly. Bacillus cereus is associated with rice (mainly fried rice) and other starchy foods such as pasta or potatoes. It may also be used as a terrorist weapon. Eschericia coli (E. coli) causes large amounts of watery diarrhea and then turns into bloody diarrhea. There are many different types of this bacterium but the worst strain can cause kidney failure and death (about 3–5% of all cases). It is transmitted by eating raw or undercooked hamburger, unpasteurized milk or juices, contaminated well water, or contaminated produce. Shigella which is know as traveler’s diarrhea, can cause diarrhea containing blood or mucus or both, and the constant urge to have bowel movements. It is transmitted in water polluted with human wastes. Clostridium botulinum (botulism) begins as blurred vision followed by problems talking and overall weakness. Symptoms then progress to breathing difficulty and inability to move arms or legs. Infants and young children are particularly at risk. It is transmitted in foods such as home–packed canned goods, honey, sausages, and seafood. Vibrio cholerae strikes mostly in the warmer months of the year and is transmitted by infected, undercooked, or raw seafood.

Parasitic Causes

Parasites rarely cause food poisoning. When they do, they are usually swallowed in contaminated or untreated water and cause long–lasting but mild symptoms. Giardia (beaver fever) causes a mild illness with watery diarrhea often lasting one to two weeks. It is transmitted by drinking contaminated water, often from lakes or streams in cooler mountainous climates. Cryptosporidium causes moderate illness with large amounts of watery diarrhea lasting two to four days. It may become a long–lasting problem in people with poor immune systems (such as people with kidney disease or HIV/AIDS or those on chemotherapy for cancer). It is transmitted by contaminated drinking water.

Toxic Causes

Toxic agents are the least common cause of food poisoning. Illness is often an isolated episode caused by poor food preparation or selection (such as picking wild mushrooms). Mushroom toxins can cause an illness ranging from mild to deadly depending on the type of mushroom eaten. Some types of mushrooms produce a nerve toxin, which causes sweating, shaking, hallucinations, and coma. Ciguatera poisoning causes moderate to severe illness with numbness of the area around the mouth and lips that can spread to the arms and legs, nausea, vomiting, muscle pain and weakness, headache, dizziness, and rapid heartbeat. It is transmitted by eating certain large game fish from tropical waters—most specifically barracuda and jacks. Scombroid causes mild to moderate illness with burning around the mouth and lips, a red rash to the upper body, dizziness, headache, and itchy skin. It is transmitted in seafood, mostly mahi–mahi and tuna, but can also be in Swiss cheese. Pesticides Cause mild to severe illness with weakness, blurred vision, headache, cramps, diarrhea, increased production of saliva, and shaking of the arms and legs. Toxins are transmitted by eating unwashed fruits or vegetables contaminated with pesticides.


The most common treatment for simple food poisoning is simple supportive care at home with clear liquids to stay hydrated, and after vomiting or diarrhea subside the gradual return to eating, beginning with a bland diet such as rice, bread, potatoes and milk. The doctor should be consulted if there is nausea, vomiting or diarrhea that lasts more than 2 days, a fever, dizziness and immediately if the person becomes unconscious, and if the symptoms occur after recent travel to foreign countries, or if people who ate the same thing are also ill. Resort to hospitalization should occur if there is vomiting blood, yellow eyes or skin, problems breathing, a swollen abdomen, swollen joints, or sharp abdominal pain that lasts more than 15 minutes.

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