Illnesses from bacteria in food are on the rise. A doctor explains how to avoid them

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Foodborne illnesses are on the rise in the United States, according to the US Centers for Disease Control and Prevention, which issued a food safety alert this week about an E. coli outbreak linked to McDonald’s Quarter Pounders. This outbreak has caused at least 49 illnesses across 10 states, including one death.

A specific ingredient has not been confirmed as the cause, but the US Food and Drug Administration has said investigators are looking at slivered onions or beef patties on Quarter Pounder sandwiches as possible sources of contamination.

This alert comes after a high-profile outbreak of listeria infections linked to Boar’s Head liverwurst and other deli meats. These cases resulted in dozens of hospitalizations and at least 10 deaths.

I wanted to know about foodborne illnesses and what can be done to improve food safety practices. What are the most common causes of foodborne infections? Why are certain infections, such as E. coli and listeria, especially problematic? What symptoms do people experience? And what should people do to reduce their chances of contracting foodborne illnesses?

To help me with these questions, I turned to CNN wellness expert Dr. Leana Wen. Wen is an emergency physician and clinical associate professor at George Washington University. She previously was Baltimore’s health commissioner, with responsibilities that included overseeing food safety.

What are the most common causes of foodborne infections?

Dr. Leana Wen: There are several bacteria, viruses and parasites that can cause foodborne infections.

The most common foodborne infection is caused by norovirus, which causes about half of all outbreaks of food-related illnesses in the US. This virus spreads easily through food and drink and from person to person through sharing utensils or touching objects that an infected person has touched and then touching your mouth.

The most common bacteria that causes foodborne illness is the Campylobacter bacteria. These infections are commonly caused by eating raw or undercooked poultry. Other common bacterial infections include salmonella, E. coli and listeria.

Why are certain infections, like E. coli and listeria, especially dangerous?

Wen: E. coli is one of the many types of bacteria that live in humans’ and other animals’ intestines. There are hundreds of strains of E. coli. One in particular, called O157:H7, can be especially dangerous, and there are outbreaks of this strain every year in the US. This is the strain that has been implicated in the McDonald’s outbreak.

This strain produces a toxin that can damage the lining of the intestinal wall and cause severe infection and bloody diarrhea. Many patients will recover after bouts of abdominal cramps and diarrhea, but some can develop a complication known as hemolytic uremic syndrome that can lead to kidney failure and even death.

As for listeria, it commonly is associated with improperly processed deli meats and unpasteurized milk. It is not particularly dangerous to most healthy people, but infection can have very serious consequences for certain groups of individuals, including older people, babies and those who are immunocompromised. There are also specific and serious dangers for pregnant women; listeria infection can result in miscarriage, stillbirth and preterm labor.

What symptoms do people experience if they contract foodborne infections?

Wen: Common symptoms are nausea, vomiting, diarrhea and abdominal pain. Some individuals may also develop fevers, body aches and other flu-like symptoms. Depending on the organism involved, there may be other symptoms, such as bloody diarrhea in the case of O157:H7.

How is foodborne infection treated?

Wen: This depends on the organism causing the infection. Most infections resolve on their own. Patients need supportive treatment with hydration but do not need specific therapy. Some benefit from antibiotics. Then there are some infections, notably O157:H7, where antibiotics are not used and in fact could worsen illness. Individuals experiencing severe abdominal cramping and bloody diarrhea or who are unable to keep down fluids should seek medical attention.

What should people do to reduce their risk of foodborne infections?

Wen: The outbreaks that make the news can give the impression that all foodborne infections are associated with restaurant or store-bought food. That’s true for a small number of cases, but most others occur at home, in our everyday lives.

Since norovirus is the most common cause of foodborne infection, let’s talk about norovirus prevention first. It’s crucial to wash hands often and well with soap and water. If this is not available, try to use hand sanitizer after touching commonly touched surfaces prior to touching your mouth.

People who have nausea, vomiting, diarrhea, stomach cramps or other symptoms that could indicate norovirus should not prepare food and should not be around others in public spaces, such as school and work.

Undercooking meat and fish is another common cause of foodborne infections. Different products require different temperatures to ensure that they are cooked through. For instance, chicken, turkey and other poultry should be cooked to 165 degrees Fahrenheit (74 degrees Celsius). Fish should be cooked to 145 F (63 C).

Always be aware of what containers and utensils you are using with raw meat. Don’t use these on other products, which then become contaminated with the bacteria from the raw meat.

Another possible cause of foodborne illness is not washing produce. Vegetables and fruits should be washed, even if they end up getting peeled. The best way is to rinse them under running water. Do not use dishwashing liquid or disinfectants.

Storage is an area to keep a close eye on, too. Two hours is the limit for keeping food safe outside the refrigerator or freezer. However, if you are outdoors and the temperature is very warm, that is reduced to one hour.

Also, do not drink unpasteurized milk or consume products made from unpasteurized milk. And pay attention to local advisories. Local health departments will keep you updated on possible foodborne illnesses associated with local stores and restaurants.

Who should take extra precautions around food safety?

Wen: There are two groups of people who need to take extra precautions. First are those who work in the food industry or who are otherwise preparing and serving food to many others. They have to make sure to use good hand hygiene and safe cooking practices so that they do not infect other people.

The second are those most vulnerable to severe illness if they contract foodborne illnesses. These are older adults, babies and young children, pregnant women, immunocompromised people and others who have severe underlying chronic conditions. They should take extra precautions to reduce their chance of becoming ill, such as avoiding deli meats and checking to ensure that the meat they are consuming was cooked to adequate temperatures.

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