Summer Food Poisoning

Context

Why is food poisoning more common in summer?

Between the 4th of July and Labor Day, there are plenty of warm weekend days when we can enjoy a summer barbecue or picnic with friends and family. Unfortunately, some of the food we share this way will be undercooked, poorly prepared, or left in the heat too long, and this is why summertime is also the peak season for people to get sick with food poisoning.

What kinds of foods are most often involved?

You can probably guess the usual suspects: hot dogs; hamburgers; coleslaw; and potato, egg, or chicken salad. But the fact is, any type of food can lead to food poisoning if it’s been poorly handled, cross-contaminated, or simply left out too long in the sun.

Animals harbor bacteria in their intestines, so undercooked or poorly refrigerated flesh meats like beef, pork, chicken, or fish are especially troublesome. Raw eggs occasionally have Salmonella and other bacteria on the outer shell, and rarely (1 in 30,000 eggs!) there may be even be Salmonella inside the egg itself.  Pasteurized milk and dairy products are safe if they have been kept cold, but any dairy product can become infected with bacteria after a few hours in the open air without refrigeration. The CDC monitors which foods are most likely to cause food poisoning.

Symptoms

What are typical symptoms of summer food poisoning?

The most common symptoms are nausea, vomiting, and diarrhea. The onset and sequence of symptoms is variable, but most cases of food poisoning begin with diarrhea, typically about 16-24 hours after ingestion of the contaminated food.

Occasionally there can be fever, or more serious symptoms such as bloody stool, significant abdominal cramping and pain, or dehydration. More rarely, food poisoning can lead to neurological symptoms, such as tingling, blurry vision, or feeling dizzy.

What should you do if you think you have food poisoning?

Food poisoning is generally self-limited, and resolves with supportive self-care, which includes rest, as well as good fluid rehydration to maintain normal urine output. Most people achieve a full recovery within 24-48 hours, with no long-term complications. However, there are certain “red flags,” which would warrant more immediate medical attention.

Diagnosis

When should you seek medical care?  

The Center for Disease Control (CDC) recommends seeking medical care under these five circumstances: bloody diarrhea, fever > 101.5 degrees, frequent vomiting, significant dehydration, or diarrhea > three days. Even in the absence of these significant symptoms, if a person has a slightly weakened immune system (e.g., young children, older adults, people with HIV or any serious chronic disease, or pregnant women), they should reach out to their doctor for advice when they come down with food poisoning,

How is food poisoning diagnosed?

There are at least 250 identified foodborne pathogens, and of these, eight cause the majority of foodborne illness. Some doctors will order stool cultures and extensive lab testing to look for bacteria and viruses, but this has been proven to be costly and inefficient, with a low yield for diagnosis. In 80% of all cases, we are unable to determine a specific microbe or toxin. Therefore, most medical societies do not feel that ancillary testing is necessary, unless there is significant illness, fever, or visible blood in the stool.

That being said, if you know the approximate amount of time that passed between when you ate the contaminated foods and when you started having symptoms, some pathogens are more likely:

Certain bacteria, such as Bacillus cereus or Staph aureas, contain a preformed toxin that causes vomiting within 1-6 hours of exposure, while other bacteria (like Clostridia perfringens) have a toxin that leads to diarrhea within 8-16 hours after exposure.

If the onset of diarrhea is >16 hours after exposure, the cause is more likely either a toxin associated with Clostridia botulinum, E. coli 0157, or Vibrio cholera, or an invasive microorganism such as Salmonella, Shigella, Campylobacter, other Vibrio, Yersinia, or Listeria.

If the onset of symptoms is 24-48 hours after exposure, the most likely cause is a norovirus infection. Norovirus is the most common cause of foodborne illness, overall.

Finally, two well-described types of food poisoning are associated with consumption of contaminated fish: Ciguatera and Scombroid poisoning both occur within an hour of eating contaminated fish, but they have slightly different clinical presentations.

Treatment

How is summer food poisoning treated?

The most important treatment is oral rehydration with fluids in sufficient amounts to produce a normal amount of urine. Pedialyte, coconut water, Gatorade, or a warm clear bouillon broth are ideal fluid choices, but even plain water can be used for rehydration.

There’s no rush to start consuming solid foods, and it’s better to avoid meats and fatty foods immediately after an episode of food poisoning. We recommend starting with a “wet and dry” diet for adults (fluids and crackers/pretzels), or a “BRAT” diet for school-aged children (Bananas, Rice, Applesauce, Toast).

There are several anti-diarrheal products, such as Lomotil or Imodium, but these should be used with caution. The body is trying to get rid of a toxin, bacteria, or virus, so it’s usually better to let the diarrhea run its own course, and just replace fluids with equal amounts of water and electrolytes.

Occasionally, diarrhea or vomiting can cause more severe dehydration, which can’t be adequately corrected with oral fluids. In those cases, intravenous fluid replacement will be required. A physician with good clinical judgement will often know, based on history alone, whether you need to be examined and given IV fluids.

For most cases of food poisoning, antibiotics are not necessary. However, fever, abdominal pain, or bloody stool may be signs of inflammatory diarrhea, which can benefit from antibiotics. If you’re experiencing these symptoms, seek medical care to discuss the risks and benefits of antibiotics.

Prevention

What are the best ways to handle, prepare, and serve dishes to avoid summer food poisoning?

Both the CDC (Center for Disease Control) and the USDA (US Dept of Agriculture) provide detailed information about food safety to prevent foodborne illness. These food preparation and storage recommendations go a bit further than the simple advice that is routinely given to Peace Corps Volunteers and international travellers to the developing world: “Boil it, cook it, peel it, or forget it.”

When it comes to preparing and handling foods for outdoor picnics and barbecues, the sure way to avoid foodborne illness is to clean, separate, cook, and chill. It’s important to clean all foods well; separate uncooked meats to avoid cross-contamination of other foods such as salads, fruits, or vegetables; cook all meats to proper temperature (typically to 145 F for beef or pork, 160 F for ground meats, and 165 F for poultry); and chill all cold foods to a cool temperature.

What kinds of picnic or BBQ dishes should you avoid, and what kinds can you feel safe about if you didn’t prepare them yourself?

If a food is served sizzling or steaming, it should be safe to eat. Unfortunately, when meat is cooked on an outdoor barbecue, it may be sizzling on the outside but still undercooked or bloody inside. The simple advice is either to use a temperature probe, or to cut the meat open and inspect carefully before eating. As for salads and other potluck dishes, beware of anything that’s been sitting out longer than two hours, especially items that contain eggs or mayonnaise.

Useful Links

A good overall source of information from the Centers for Disease Control and Prevention (CDC)

Simple advice from the US Dept of Agriculture (USDA)

A patient-friendly summary of causes, risk factors, symptoms, diagnosis, and treatment (Up-to-Date)

More detailed information about diagnosis and management of foodborne illness (AAFP)

Specific information about diagnosis and treatment of diarrhea (AAFP)

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