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Coxiella burnetii Raw Milk Outbreak

Posted in Our Blog on June 7, 2023

A Montana County issued a statement this week reminding residents of the dangers of consuming raw milk.  Two cows from a farm that sells unpasteurized milk at a local farmers market tested positive for Coxiella burnetii, a bacteria that causes Q fever. Here’s what we know about this Coxiella burnetii Raw Milk Outbreak:


Raw Milk


Raw milk, otherwise known as unpasteurized milk, used to be illegal.  That is, after it was just called milk.


This dates back to the 1980’s where a large Salmonella outbreak in Missoula County originating with unpasteurized milk from a local dairy farm sickened more than 100 people, half of which were under the age of 14.  To make matters worse, the particular strain involved in the outbreak was also multi-drug resistant – meaning many of the antibiotics typically used to treat this type of bacterial infection would not work.  As a result, 15% of those who became sick required hospitalization.


An inspection during the outbreak revealed a clean bill of health for the dairy farm.  No sanitation laws or practices were broken.  Everything was maintained at industry standards.


After that outbreak, the state of Montana changed the laws regarding milk production and sales.  The law indicated that all milk sold to consumers had to be pasteurized.


As a result, deaths and diarrheal illnesses in young children showed a significant decline.


New Law Lifts Raw Milk Restriction


Before the laws, most milk was just raw milk.  Milk was milk.  After raw milk was deemed illegal and pasteurization was a legal requirement, folks did not have access to raw milk unless they had cows and milked them for their own use.


That all changed in 2021.  Unpasteurized milk sales are now allowed in the state of Montana at the farm, farmers markets, and other traditional community events, with a few conditions.


First, the farm must have a herd of no more than five lactating cows.  This restricts the sales to small family operations.  Additionally, the seller must inform the end consumer that the product is not licensed, certified, packaged, labeled, or inspected under any official regulation.


Two Cows Test Positive


According to health officials, milk that was recently sold at a local farmers market came from a herd where two cows tested positive for the harmful bacterium, Coxiella burnetii.  This bacteria is responsible for the illness, Q fever.


One of the positive cows did not contribute to the milk production as she has not yet produced milk.  The other cow, however, produces about 10% of the farmer’s average yield.  There is no information on whether or not the milk was tested for the bacteria.


“We don’t know if the cow was shedding the bacteria at the time it was milked, or if that cow’s milk was sold at the farmers market,” said Environmental Health Director Shannon Therriault.  “So we can’t say for sure whether anyone was exposed.  However, what we do know is that unpasteurized milk can contain harmful bacteria that can make you and your loved ones sick.”


Public Service Announcement


In response to these findings, the Missoula Public Health City-County Health Department issued a Public Service Announcement on May 19, 2023 titled “Missoula County Health Official Issue Warning About Drinking Raw Milk Following Possible Bacteria Exposure.”


In this statement, the office indicated that drinking raw milk has increased in popularity and warned against the dangers of consuming the unpasteurized product.


“While drinking ‘raw’ milk has become more widespread in recent years, we want people to know that it can easily be contaminated with harmful bacteria, even when the milking operation is well-run,” Therriault said.


Unpasteurized milk products have been linked to many outbreaks in the past.  E. coli, Campylobacter, Salmonella, Brucella, Listeria, and cryptosporidium have all been linked to raw milk at one time or another.


What is Q Fever?


Q fever is the disease associated with infection with the bacteria Coxiella burnetii.  This bacteria naturally infects certain livestock such as goats, sheep, and cattle.  The bacteria can be found in the birth products (placenta, amniotic fluid, etc.), feces, urine, and the milk of an infected animal.


People can become infected by breathing in contaminated dust or drinking unpasteurized milk from an infected animal.  According to the Centers for Disease Control and Prevention (CDC) about half of those infected with Coxiella burnetii will become ill.  Symptom onset is quite a while from exposure date.  It can take up to 2 to 3 weeks after being exposed to the bacteria before symptoms appear.



Symptoms of Q fever range from mild to severe.  Typical symptoms include:


  • Fever
  • Chills or sweats
  • Fatigue (tiredness)
  • Headache
  • Muscle aches
  • Nausea, vomiting, or diarrhea
  • Chest pain
  • Stomach pain
  • Weight loss
  • Non-productive cough


Severe Infection

Severe infection can affect the lungs (pneumonia) and/or the liver (hepatitis).  Women who are infected during pregnancy are at higher risk for miscarriage, stillbirth, pre-term delivery, or low infant birth weight.


Chronic Q Fever


A rare, more serious form of infection is called Chronic Q fever.  This happens in less than 1 out of 20 individuals who become infected with the Coxiella burnetii bacteria.


This illness can develop months or even years following the initial Q fever infection.  This type of infection often attacks one or more heart valves, causing a condition known as endocarditis.  Symptoms of endocarditis include night sweats, fatigue, shortness of breath, weight loss, or swelling of limbs.  Specialized tests are required to diagnosis endocarditis.


People with existing heart valve disease, blood vessel abnormalities, or those with weakened immune systems are more susceptible to this serious complication.  Women who are infected during pregnancy may also be at higher risk for developing Chronic Q fever.


This illness can be serious, even fatal, if not treated correctly.  Treatment often involves months of antibiotic treatment to rid the body of this harmful bacteria.


Has Anyone Fallen Ill?


At this time, there have not been any reported cases of Q fever; however, the milk from an infected cow was likely in circulation.  With the extended incubation period of the illness, it may be several weeks before people begin falling ill.


If you have consumed raw milk, it is a good idea to pay attention to your body and monitor for symptoms.  Reach out to you health care provider and indicate you may have been infected with Coxiella bunetii.