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MN Study: Raw Milk Illnesses Greatly Underreported

Despite the somewhat commonplace occurrence of illness outbreaks associated with unpasteurized milk, the number of illnesses linked to drinking raw milk is much higher than those counted in outbreak reports, according to an analysis published by the Minnesota Department of Health on Wednesday.

Looking at 10 years of health department data between 2001 and 2010, researchers found that the number of patients in Minnesota with laboratory-confirmed foodborne infections who said they drank raw milk within a week of falling ill was 25 times greater than the number of cases actually counted in raw milk outbreaks over the same time period.

What’s more, researchers also estimated that, out of all the Minnesotans who drank raw milk from 2001 to 2010, up to 17 percent may have fallen ill with an intestinal infection from doing so. That’s assuming the patients didn’t eat some other contaminated food, which is a big “if” but not unrealistic, said Trisha Robinson, epidemiologist for the Minnesota Department of Health (MDH) and lead author of the study.

The findings suggest that outbreak cases – typically the only cases that get attention – represent only a small fraction of the actual number that occur.

“This is something that is very generalized throughout the nation,” Robinson said. “The risk of raw milk is far greater than what’s reported, whether you’re in Minnesota or California or Pennsylvania.”

Most surprisingly, Robinson said, was the degree to which children who drank raw milk were disproportionately affected by sporadic illness, with the milk often coming from their immediate family’s own dairy or that of a relative. Of the children sickened who were younger than 5 years of age, 76 percent were served milk from a family member’s farm.

“It really goes to show that even when you know your farmer or know where your milk comes from, people can still get sick,” Robinson said.

Sporadic cases pop up in routine surveillance

The new MDH paper is the first of its kind to compare sporadic illnesses to raw milk outbreak cases, according to Robinson. The authors combed back through the years of illness data they had collected by interviewing patients who had sought medical attention and tested positive for a gastrointestinal infection such as E. coli, Campylobacter or Salmonella.

When someone goes to the doctor and ends up testing positive for one of those pathogens, the healthcare provider is required by law to inform the health department. The health department then follows up with the patient, interviewing them about a range of foods they might have eaten in the previous week before falling ill.

From 2001 to 2010, Minnesota recorded 21 lab-confirmed illnesses from five raw milk outbreaks. In that same time, the state confirmed 530 foodborne illnesses in people who had consumed raw milk within a week of coming down with symptoms. A total of 3.7 percent of people with sporadic infections reported drinking raw milk in that time frame, compared to the 2.3 percent of Minnesota’s total population estimated to drink raw milk in a given week.

“Outbreaks are just the tip of the iceberg, and that’s why it’s so important we think about the people who are sporadic cases,” Robinson said.

Children sickened at disproportionate rate

Of all the illnesses associated with raw milk consumption, 59 percent were 20 years old or younger, 38 percent were 10 or younger, and 25 percent were 5 or younger.

Children are generally more susceptible to foodborne pathogens because their immune systems are still developing.

According to the authors, previous studies have shown that 30 to 50 percent of dairy producers surveyed were unaware that their raw bulk tank milk may contain disease-causing microorganisms.

That figure is especially concerning given how many farmers are known to serve raw milk to children in their family, Robinson said.

“If consumers can see this information, hopefully they’ll better understand the risk if they choose to consume raw milk,” Robinson said. “It’s important they consider the risk for both themselves and their family.”

© Food Safety News
  • kevin1

    Would love to see a comparison to incidents of persons sickened by pasteurized milk, I’d bet the numbers aren’t widely different.

  • Leah Dunn

    I wonder. Since the majority of cases came from those living on a dairy, couldn’t the infections have come from the animals themselves? Why is it assumed it came from raw milk when by all rights it could have come in on the farmers shoes.

  • kevin47

    What is the basis for the 18 multiplier? Is salmonella-related illness under-reported by a factor of 18? The paper cites a number of sources, but conveniently fails to reference them in-text, so one would have to dig through every single page of every single citation in order to verify a figure that is essential to their final calculation.

    Then, they take an estimate of the number of Minnesotans who (they estimate) consume raw milk in any given week, and apply their multiplied figure to that number. To which:

    1. Is there no under-reporting of raw milk consumption at all? Why not devise a multiplier for the denominator in this case?

    2. The scientists assume that the number of Minnesotans who consume raw milk in any given week is EQUAL TO the number of Minnesotans who have consumed it in the past 10 years. This is especially absurd when you consider many of those studied are less than 10 years old.

    The paper ends with the assertion that it isn’t really possible to determine whether those who consumed raw milk actually got sick from raw milk, or from other cattle-related pathogens. Considering the majority of those studied had also come into contact with cattle, this seems a glaring concession.

    The purpose of this paper is to ramp up the number of those made ill by raw milk as much as possible. That’s advocacy, not science.