Salmonella outbreaks are on the rise. Should doctors be concerned?

Alistair Gardiner | November 05, 2021

With Thanksgiving just around the corner, many people are getting excited about the gluttonous feasts ahead. That’s all well and good—unless the unsavory Salmonella bacteria comes along and spoils the party.

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Chopping lettuce on cutting board

Salmonella outbreaks are on the rise and the bacteria is turning up in foods you might not expect.

With several Salmonella outbreaks in the news recently, now is a good time to review the basics of salmonella infection, which causes fever, stomach cramps, diarrhea, and sometimes leads to infections in urine, blood, bones, joints, or the nervous system.

Of special concern for doctors is that an estimated one in five Americans has an underlying condition that makes them more vulnerable to illness caused by Salmonella. That means that some of your patients could be at a higher risk.

According to the CDC, Salmonella bacteria infect roughly 1.35 million Americans every year, leading to an estimated 26,500 hospitalizations and 420 deaths annually, mostly through food contamination.

If you think that poultry and eggs are the only sources of Salmonella, you may be surprised to learn that various fruits and vegetables have driven several recent outbreaks. For example, in late October, the CDC issued a Food Safety Alert for a Salmonella outbreak linked to onions. Earlier in October, the CDC warned about an outbreak originating from packaged salad greens. Last year, the agency issued warnings about Salmonella-infected peaches, mushrooms, and onions.

In light of these increasing outbreaks, here’s a rundown of the most up-to-date information on Salmonella, who is most vulnerable to foodborne illnesses, and how people can take precautions to avoid them. 

It’s not just chicken and eggs

According to the CDC, people can become infected with Salmonella by eating contaminated food or drinking contaminated water, or by coming into contact with infected animals or animal feces. And “contaminated food” doesn’t just mean pork, chicken, turkey, and eggs; you can also get a Salmonella infection from a range of vegetables, including sprouts and leafy greens. 

The contamination of leafy greens and other veggies or fruits can occur at any stage of their journey from field to plate. From animal feces in the water used to grow them, to the hands of the employees who handle them in processing facilities and stores, potentially harmful germs are everywhere (including your kitchen).

From 2014-2018, the CDC received reports of 51 foodborne disease outbreaks linked to leafy greens, five of which affected multiple states. The outbreaks, which involved the recall of foods like packaged lettuce and romaine salad, resulted in 1,406 recorded illnesses. 

The CDC, however, believes that this figure may “represent only a small proportion of all illnesses caused by contaminated leafy greens in those years.” Some outbreaks don’t lead to public warnings, because the food is no longer on store shelves by the time it’s identified as a source of Salmonella. On top of that, some people may not attribute their illness to contaminated food.

Evidence suggests that the outbreaks recorded by the CDC are representative of a larger shift in the epidemiology of foodborne Salmonella. For example, a study published in the Journal of Global Biosecurity in 2020 concluded that a higher number and proportion of outbreaks are now associated with fruit and vegetables, rather than animal products.

Authors of the study note that chicken and eggs are the most common food vehicles associated with foodborne illnesses. However, they examined data from literature on Salmonella outbreaks caused by fruit and vegetables globally, identifying events in North America, Europe, and Australia. Authors concluded that “the proportion of Salmonella outbreaks caused by fruit and vegetables has been increasing, as observed in both the United States of America (USA) and Australia.” 

From 1973-1997, outbreaks linked to fruits and veggies increased from 0.7%-6% and this figure jumped to 13% by 2005. Notably, researchers also found that cucumbers are a novel and increasingly prevalent vehicle for the bacteria, citing various outbreaks in the United States linked with cukes from 2013-2018.

Authors posited that an increase in fruit and vegetable consumption, as well as an increase in the distance the produce travels to get to us, may be part of the cause for the trend. Another cause, according to a study published in Foodborne Pathogens and Disease, might be climate change, which may increase the spread of foodborne pathogens, the authors noted. 

In order to explore the links between global warming and the increased spread of foodborne pathogens, researchers examined meteorological data collected from three states between 2002-2011, and analyzed the correlation with salmonellosis. They found that gastrointestinal infection with bacterial pathogens was positively correlated with ambient temperature, and concluded that warmer temperatures allow bacteria to replicate more quickly.

Which of your patients are most vulnerable?

Most Salmonella bacteria cause an illness called salmonellosis, symptoms of which include diarrhea, fever, and stomach cramps. Symptoms typically begin from 6 hours to 6 days after infection, and most people recover without treatment. But some patients may require antibiotics; some require hospitalization.

Populations most likely to experience severe illnesses are: 

  • Children younger than 5 years

  • Adults older than 65 years

  • People with weakened immune systems, including those with HIV infection or patients undergoing chemotherapy

  • People over the age of 50 who have an underlying condition, like heart disease

  • Patients undergoing transplants

  • Pregnant women and their newborns

  • Infants (under 12 months) who are not breastfed

  • People taking certain medicines, like stomach acid reducers

According to Christopher Braden, MD, a physician with the CDC, an estimated 20% of the US population falls into one of the above categories. For these individuals, Salmonella infection could lead to long-term health complications or even death.

Tips to avoid Salmonella 

The best way for your patients to avoid Salmonella infection is to adopt some basic hygiene practices. Try to avoid buying produce that’s bruised or damaged, and make sure you keep your meat and veggies separate while shopping. Keep them refrigerated until use.

Before you start preparing food, make sure your hands and kitchen surfaces are clean—and wash or scrub all fruits and veggies under running water before cooking. Use different cutting boards for meat and other foods. Once you’ve finished cooking, don’t forget to put all uneaten food back in the refrigerator. 

To cook a turkey safely, click here to follow the CDCs food safety tips for preparing your holiday bird.  

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