Brucellosis: Symptoms, Causes, and Treatment
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick answer
Brucellosis is a bacterial infection that spreads from animals to people, most often through raw dairy products. It causes flu-like symptoms such as fever, chills, heavy sweating, weakness, and joint, muscle and back pain that may come and go for months. Treatment is antibiotics taken for at least six weeks to relieve symptoms and prevent relapse and complications. [1] [2]
What the research says
According to PubMed:
Doxycycline plus streptomycin beat doxycycline plus rifampicin. In a Cochrane review of 25 randomized trials, the 8 studies (694 participants) comparing these two regimens found more treatment failure with the rifampicin combination (RR 1.91, 95% CI 1.07 to 3.42) and more relapse (RR 2.39, 95% CI 1.17 to 4.86). Streptomycin needs daily injections, so access to care and cost matter. (Yousefi-Nooraie et al., DOI).
Six weeks of treatment worked about as well as eight. In a randomized trial of 144 patients with uncomplicated brucellosis (72 per arm), relapse was 13.9% after 6 weeks of doxycycline plus rifampicin (with streptomycin for the first 7 days) and 9.7% after 8 weeks, a difference that was not significant. (Sofian et al., DOI).
Raw dairy and animal contact top the risk list in the Middle East. A review of 92 studies from 1993 to 2024 found unpasteurized dairy consumption and close animal contact were the predominant risk factors, with the highest prevalence in Oman, Lebanon, and Kuwait. (Dadar et al., DOI).
Study details are from PubMed abstracts.
Key facts at a glance
Key fact | What to know |
Cause | Bacteria carried by cattle, goats, sheep, pigs, deer, camels, and other animals [1] |
Most common spread route | Eating raw or unpasteurized dairy products [1] |
Symptoms feel like | The flu, with fever, joint pain, and heavy fatigue [1] |
Treatment length | Antibiotics for at least six weeks [2] |
Chronic cases | Symptoms can last for years, even after treatment [1] |
What is brucellosis?
Brucellosis is an infection caused by bacteria. It spreads from animals to people. [1]
Most often, people get brucellosis by eating dairy products that are raw or have not been treated to make them safer, a process called pasteurization. In certain workplaces the bacteria can be inhaled. People can also get brucellosis through direct contact with infected animals. [1]
The infection can often be treated with antibiotics. However, treatment takes several weeks to months, and the infection can come back. [1]
What are the symptoms of brucellosis?
Symptoms may show up anytime from a few days to a few months after infection. They are like those of the flu. [1]
Symptom | What it looks like |
Fever | A temperature that goes up fast or lasts [1] |
Chills | Shivering and feeling cold [1] |
Loss of appetite | Eating much less than usual [1] |
Heavy sweating | Sweating much more than usual [1] |
Weakness and tiredness | Unusual fatigue that persists [1] |
Pain | Joint, muscle, and back pain [1] |
Headache | Pain in the head [1] |
Chronic brucellosis
Symptoms may disappear for weeks or months and then return. Some people develop long-term, called chronic, brucellosis. People with chronic infection have symptoms for years, even after treatment. Long-term symptoms may include tiredness and repeated fevers. [1]
Chronic brucellosis can also cause inflammation of the inner lining of the heart chambers, called endocarditis, and several forms of arthritis. Arthritis may affect the joints generally, the spinal bones (spondylitis), or the joints where the spine and pelvis connect (sacroiliitis). [1]
When should you see a doctor about brucellosis?
Brucellosis can be hard to diagnose, especially in the early stages. At that point, it often seems like other conditions, such as the flu. [1]
Make a medical appointment if you are at risk for brucellosis and you have a fever that goes up fast or lasts, or muscle aches or unusual weakness. Mention any relevant exposures, such as recent travel, work with animals, or raw dairy products, since this information helps with diagnosis. [1] [2]
What causes brucellosis and how does it happen?
Brucellosis bacteria are carried by many animals. The bacteria may or may not cause animals to be sick. [1]
Animals that carry bacteria that can infect humans include cattle, goats, and sheep; pigs and wild hogs; dogs, especially those used in hunting; deer, elk, caribou, and moose; bison; and camels. A form of brucellosis also affects harbor seals, porpoises, and certain whales. [1]
The three main spread routes
Route | What happens | Who is at risk |
Eating raw animal products | Brucella bacteria in the milk of infected animals can spread to humans through unpasteurized milk, ice cream, butter, and cheeses. The bacteria can also come from raw or undercooked meat of infected animals. [1] | Anyone who eats or drinks unpasteurized dairy, especially while traveling |
Breathing in bacteria | Brucella bacteria spread easily in the air. [1] | Farmers, hunters, laboratory workers, and slaughterhouse workers |
Touching blood and body fluids | Bacteria in the blood, semen, or placenta of an infected animal can enter a person's blood through a cut or other wound. [1] | Veterinarians, farmers, hunters, and slaughterhouse workers |
Contact with animals, such as touching, brushing, or playing with them, does not cause infection, so people rarely get brucellosis from their pets. Even so, people who have weakened immune systems should avoid touching dogs that have the disease. [1]
Can people spread it?
Brucellosis is not likely to spread from person to person. But rarely, the disease can be passed during birth or through breast milk. Rarely, it may spread through sexual activity or through infected blood or bone marrow transfusions. [1]
What are the risk factors for brucellosis?
Brucellosis is rare in the United States. But it is more common in other parts of the world, especially in the regions below. [1]
Higher-risk region | Details |
Southern Europe | Including Portugal, Spain, Turkey, Italy, Greece, and southern France [1] |
Eastern Europe | More common than in the United States [1] |
The Americas | Mexico, South and Central America, and the Caribbean [1] |
Asia, Africa, and the Middle East | More common than in the United States [1] |
Jobs at higher risk
People who work with animals or who come into contact with infected blood are at higher risk of brucellosis. Examples include veterinarians, dairy farmers, ranchers, slaughterhouse workers, hunters, and microbiologists. [1]
Travelers to higher-risk regions who eat raw dairy products are also at increased risk, since the bacteria can be present in unpasteurized milk, cheese, and ice cream. [1]
What complications of brucellosis should you watch for?
Brucellosis can affect almost any part of the body, including the reproductive system, liver, heart, and central nervous system. Chronic brucellosis may cause complications in just one organ or throughout the body. [1]
Complication | What happens |
Endocarditis | Inflammation of the inner lining of the heart chambers. It is one of the most serious complications: untreated, it can damage or destroy the heart valves, and it is the main cause of death from brucellosis. [1] |
Arthritis | Pain, stiffness, and swelling in the joints, especially the knees, hips, ankles, wrists, and spine. Spondylitis and sacroiliitis can be hard to treat and may cause lasting damage. [1] |
Epididymo-orchitis | Infection of the epididymis, the coiled tube that stores and transports sperm, which can spread to the testicle. It causes swelling and pain that may be severe. [1] |
Spleen and liver infection | The spleen and liver can get larger than usual. [1] |
Central nervous system infection | Inflammation of the membranes around the brain and spinal cord (meningitis) or of the brain (encephalitis), possibly life-threatening illnesses. [1] |
How is brucellosis diagnosed?
Diagnosis of brucellosis is made by testing blood or the spongy matter inside the bones, called bone marrow. Other tests can help find complications of brucellosis. [2]
Diagnostic step | What it shows |
Blood or bone marrow test | Confirms the diagnosis of brucellosis [2] |
X-rays | Changes in the bones and joints [2] |
CT scan or MRI scan | Areas of the brain or other tissues that might be affected by the infection [2] |
Cerebrospinal fluid culture | Infections such as meningitis and encephalitis in the fluid around the brain and spinal cord [2] |
Echocardiography | Signs of infection or damage to the heart, using sound waves [2] |
During the physical exam, your healthcare professional may ask you to move your joints to check for pain and stiffness, check your reflexes and the strength of your muscles, and press on your belly to see if organs are larger than usual or tender. [2]
What are the treatment options for brucellosis?
Treatment for brucellosis aims to relieve symptoms, prevent the disease from coming back, and prevent complications. [2]
Antibiotics. Treatment involves taking antibiotics for at least six weeks. Symptoms may not go away completely for several months. [2]
Relapse. The disease also may return and become long-term, called chronic. [2]
Complications. Brucellosis can affect specific organs, such as the heart or joints, so your healthcare team may need to treat those problems as well. [1]
How can you prevent brucellosis?
Avoid raw dairy. Do not eat dairy foods that have not been pasteurized. In recent years in the United States, few cases have been linked to raw dairy from domestic herds. Still, it is best to avoid unpasteurized milk, cheese, and ice cream, no matter where they come from. If you are traveling to other countries, avoid all raw dairy foods. [1]
Cook meat all the way. Cook a whole cut of meat until it reaches an inside temperature of 145 F (63 C) and let it sit for at least three minutes before cutting or eating, which makes it medium done. Cook ground meat to 160 F (71 C), which is well done. Cook poultry, including ground poultry, to 165 F (74 C). Do not eat undercooked meats. [1] [4]
Wear gloves. If you are a veterinarian, farmer, hunter, or slaughterhouse worker, wear rubber gloves when handling sick or dead animals or animal tissue. Wear gloves when helping an animal give birth. [1]
Take care in high-risk workplaces. For laboratory work, make sure all biosafety conditions are being met. Slaughterhouses should also take protective measures, including wearing protective clothing and keeping the killing floor apart from other work areas. [1]
Vaccinate farm animals. In the United States, brucellosis in livestock is rare due to vaccination. Because the brucellosis vaccine is live, people who get stuck by a needle while vaccinating animals can get the disease. They need to be treated. [1]
How should you prepare for a brucellosis appointment?
You may start by seeing your healthcare professional. Then, you may be referred to an infectious disease specialist. A diagnosis of brucellosis depends on your coming into contact with the bacteria that cause the disease, so your healthcare team will need as much information as possible about that. [2]
Before your appointment, you may want to write down the answers to the following questions. [2]
When did you begin having symptoms?
Have you had any raw dairy products, such as milk or goat cheese?
Does your job involve contact with animals or with animal tissues?
Have you traveled to countries other than the United States during the past year?
Do you work in a lab where infectious bacteria are present?
Have you gone hunting recently?
Conclusion
Brucellosis is an infection that moves from animals to people, most often through raw dairy. Symptoms feel like a stubborn flu, can take months to fully clear, and may come back as chronic brucellosis. [1]
The key to a good outcome is a fast, accurate diagnosis and a full course of antibiotics lasting at least six weeks. If you have fever, joint pain, and unusual fatigue after travel, animal exposure, or raw dairy, do not wait for it to pass on its own. [1] [2]
Next steps: If you or a loved one may have brucellosis or another infection from animals, talk with a healthcare professional who can confirm the diagnosis and start treatment.
Frequently asked questions
Is brucellosis contagious from person to person?
Person-to-person spread is unlikely, though rarely the disease can pass during birth, through breast milk, through sexual activity, or through infected blood or bone marrow transfusions. [1]
How long does brucellosis treatment take?
Treatment involves taking antibiotics for at least six weeks, and symptoms may not go away completely for several months. The disease can also return and become chronic. [2]
Can brucellosis be cured?
The infection can often be treated with antibiotics, but treatment takes weeks to months, the infection can come back, and some people develop long-term brucellosis with symptoms lasting years. [1] [2]
Does brucellosis cause a rash?
A rash is not among the symptoms listed by Mayo Clinic. The main symptoms are flu-like: fever, chills, heavy sweating, weakness, tiredness, and joint, muscle, and back pain. [1]
Where in the world is brucellosis most common?
Brucellosis is rare in the United States but more common in southern and eastern Europe, Mexico, South and Central America, Asia, Africa, the Caribbean, and the Middle East. [1]
This article is for general education and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional about your individual situation.
References
Mayo Clinic Staff. Brucellosis - Symptoms and causes. Mayo Clinic. December 24, 2025. https://www.mayoclinic.org/diseases-conditions/brucellosis/symptoms-causes/syc-20351738
Mayo Clinic Staff. Brucellosis - Diagnosis and treatment. Mayo Clinic. December 24, 2025. https://www.mayoclinic.org/diseases-conditions/brucellosis/diagnosis-treatment/drc-20351744
Centers for Disease Control and Prevention. About brucellosis. CDC. June 2, 2026. https://www.cdc.gov/brucellosis/about/index.html
FoodSafety.gov. Cook to a safe minimum internal temperature. FoodSafety.gov. November 21, 2024. https://www.foodsafety.gov/food-safety-charts/safe-minimum-internal-temperatures
Yousefi-Nooraie R, Mortaz-Hejri S, Mehrani M, et al. Antibiotics for treating human brucellosis. Cochrane Database Syst Rev. 2012;10(10):CD007179. PMID 23076931. https://doi.org/10.1002/14651858.CD007179.pub2
Sofian M, Velayati AA, Aghakhani A, et al. Comparison of two durations of triple-drug therapy in patients with uncomplicated brucellosis: a randomized controlled trial. Scand J Infect Dis. 2014;46(8):573-577. PMID 24934986. https://doi.org/10.3109/00365548.2014.918275
Dadar M, Al-Khaza'leh J, Fakhri Y, et al. Human brucellosis and associated risk factors in the Middle East region: a comprehensive systematic review, meta-analysis, and meta-regression. Heliyon. 2024;10(14):e34324. PMID 39100474. https://doi.org/10.1016/j.heliyon.2024.e34324
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