Food poisoning can be caused by bacteria, viruses, parasites or toxins produced by germs in contaminated food.
Most mild cases can be managed with rest and fluids, but bloody diarrhea, high fever, severe pain or dehydration require medical attention.
Consumers can reduce their risk by washing their hands, preventing cross-contamination, cooking foods thoroughly and refrigerating perishables promptly.
The Cyclospora outbreak no doubt has consumers carefully considering what they eat, in order to avoid the parasite that has sickened over 2,000 people in the U.S. It’s just one example of food poisoning cases that are increasing as supply chains become intertwined.
While most food poisoning cases are resolved without medical treatment, an infectious-disease specialist says consumers should know which symptoms signal something more serious.
Foodborne illness can result from bacteria, viruses, parasites or toxins produced by bacteria in food, according to Dr. Poonam Bai, an infectious-disease physician at Penn State Health and assistant professor at Penn State College of Medicine.
Although food poisoning often resembles a common stomach bug, the source is contaminated food or drink. Symptoms can include nausea, vomiting, diarrhea, stomach cramps and fever.
The timing and severity of those symptoms may provide clues about the cause.
Some illnesses result from toxins already present in food. Symptoms can begin within a few hours of eating and commonly include nausea, vomiting and diarrhea. These cases often improve within about a day, Bai said.
Other illnesses are caused by infection with bacteria such as Salmonella, Shigella or E. coli; viruses such as norovirus; or parasites such as Cyclospora. Symptoms may take days—or sometimes longer—to appear and can be more persistent.
That delay means the food that made someone sick may not be the last thing they ate.
When to call a doctor
Most people with mild food poisoning can recover at home by resting and replacing fluids lost through diarrhea or vomiting. Bai recommends taking small sips of water or an electrolyte drink and eating small amounts of bland food, such as bananas or crackers, as tolerated.
Consumers should seek medical care for severe abdominal pain, bloody diarrhea, persistent vomiting, high fever or signs of dehydration.
The Centers for Disease Control and Prevention recommends contacting a healthcare provider for diarrhea lasting more than three days, a fever above 102 degrees, vomiting that prevents a person from keeping liquids down or dehydration symptoms such as dry mouth, reduced urination and dizziness when standing.
Adults 65 and older, young children, pregnant women and people with weakened immune systems face a higher risk of serious illness and should be especially cautious.
Persistent watery diarrhea may be a sign of cyclosporiasis, particularly if it begins after eating fresh produce or a restaurant salad. Other possible symptoms include cramping, bloating, nausea, fatigue, loss of appetite and weight loss.
Cyclospora symptoms commonly begin about one to two weeks after a person eats contaminated food. Doctors can diagnose the infection using a stool test, and prescription medication is available to treat it.
Food may look and smell normal
One of the challenges of preventing food poisoning is that contaminated food does not necessarily look, taste or smell spoiled.
“There is no way to tell just by looking at it,” Bai said.
Washing fruits and vegetables under running water may reduce contamination, but it cannot remove every bacterium, virus or parasite. Consumers should also follow recall instructions and discard any food identified by health authorities as potentially contaminated.
The CDC recommends four basic food-safety practices: clean, separate, cook and chill.
Hands should be washed with soap and water for at least 20 seconds before, during and after food preparation. Raw meat, poultry, seafood and eggs should be kept away from foods that are ready to eat, including in grocery carts and refrigerators.
A food thermometer is the safest way to determine whether meat and poultry have reached the proper internal temperature. Perishable foods and leftovers should be refrigerated within two hours—or within one hour when temperatures are above 90 degrees.
“Make sure hot food stays hot and cold food stays cold,” Bai said.