CDC Warns of Multi-State Salmonella Outbreak Linked to Flour

The Centers for Disease Control and Prevention are warning the public about a multi-state outbreak of Salmonella linked to raw flour, according to an investigation notice published March 30.

The CDC’s investigation is ongoing, and the agency has yet to identify a specific brand of flour linked to the outbreak. So far, 12 people have been sickened across 11 states, and three people have been hospitalized from their illnesses. As of April 5, no deaths have been reported as a result of the outbreak.

Most people sickened and spoken to by officials reported eating raw dough or batter made with flour before falling ill, and flour was the only common ingredient.

Though Salmonella outbreaks are known to be linked to raw eggs or uncooked meat, the CDC is urging people to be aware that flour—though it doesn’t look like a raw food—is still considered raw, and eating it before it’s been heat-treated or baked can cause food poisoning. Here’s what to know.

Why Is Flour Linked to Salmonella?

Salmonella infections are much more common than you may realize—in fact, the CDC reports that Salmonella bacteria causes more foodborne illnesses than any other bacteria.

Salmonella infantis—the strain of Salmonella identified in the current outbreak—can contaminate foods like eggs, chicken, raw flour, and even fruits and vegetables. Salmonella is killed by high heat, but can survive and multiply at temperatures between 40℉ and 140℉, which is known as the temperature “Danger Zone.” This is why raw foods, like raw meat, eggs, and sprouts, carry a high risk of Salmonella contamination.

Even though you may not think of flour as a raw food, flour that’s used in baking and cooking is considered raw and isn’t safe to eat unless it’s been properly and thoroughly baked or cooked to kill any potential bacteria, including Salmonella infantis.

“Flour is considered raw because it is processed from grain without any bacterial reduction step (such as heating),” Martin Bucknavage, MS, MBA, a Senior Food Safety Extension Associate and Team Lead at Penn State’s Department of Food Science, told Health. “This contamination occurs in the field, and without a reduction step such as cooking, the pathogen remains present in the flour.”

Eating contaminated food isn’t the only way you can become sick from Salmonella. You can also be exposed through drinking contaminated water or not washing your hands after handling animals and products carrying Salmonella. However, in developed countries like the US, the most common source of Salmonella infection is food.

Signs and Symptoms of Salmonella Infection

Though the CDC has so far reported 12 Salmonella-related illnesses, it’s likely that the total number of illnesses from this outbreak is much higher; for every confirmed and reported of Salmonella infection, or salmonellosis, around 30 other cases are not reported.

It can also take up to four weeks to determine if a person’s illness was related to a Salmonella outbreak, due to extensive laboratory tests that are performed is salmonellosis is suspected.

Most people who become ill from Salmonella experience mild symptoms—such as diarrhea, fever, and stomach cramps—that don’t usually require medical treatment. These symptoms can develop any time between six hours and six days after ingesting a food contaminated with Salmonella.

A full recovery from illness caused by Salmonella can take up to seven days after the onset of symptoms.

Some populations, however, including older adults, children, and people with weakened immune systems, are at a greater risk for developing more serious symptoms that may require medical intervention or even hospitalization.

It’s important to contact your healthcare provider right away or seek emergency medical care if you or someone you know exhibits any of the following symptoms after consuming foods that may have been contaminated with Salmonella:

• A fever higher than 102℉
• Diarrhea that doesn’t improve after three days 
• Bloody diarrhea
• An inability to keep liquids down due to vomiting 
• Signs of dehydration, including low urine output, a dry mouth and throat, and feeling dizzy when you stand up 

These symptoms may indicate a serious Salmonella infection that requires immediate medical attention.

How to Stay Safe When Working with Raw Flour

It’s never safe to consume raw flour and the CDC warns that ingesting even a small amount of dough or batter made with raw flour can make you sick. This includes tasting cooking dough and cake batter before it’s been cooked. 

Children, older adults, and people who are immunocompromised should be especially careful to avoid consuming raw flour as these populations are more at risk of developing severe Salmonella infections. 

It’s also important to note that you can become sick from handling flour and products made with raw flour, like crafts and homemade play clay.

“There is always a risk when young children work with raw flour to make things such as [play clay],” Bucknavage said. “In these cases, children should be supervised to prevent them from putting it or their flour-containing fingers in their mouth. Hands should be washed thoroughly afterwards and surfaces should be cleaned with warm water and soap. Raw dough should be disposed of after use.”

Here are some CDC-approved tips to help you and those around you stay safe when working with raw flour:

• Thoroughly cook all dough and batter made with raw flour before eating
• Never consume raw dough or batter made with raw flour
• Thoroughly wash all bowls and utensils with warm water and soap after baking or cooking with raw flour
• Keep raw flour in a container separated from foods typically consumed raw, like fruits 
• Use heat-treated flour in crafts and homemade play clay recipes.

As the CDC continues to investigate the Salmonella outbreak in flour, the agency is urging everyone to be vigilant about food safety while using raw flour and avoid eating raw cookie dough or cake batter.