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Brucellosis is a bacterial infection that occurs from contact with animals carrying brucella bacteria.


Brucella can infect cattle, goats, camels, dogs, and pigs. The bacteria can spread to humans by:

  • Coming in contact with infected meat or the placenta of infected animals
  • Eating unpasteurized cheese
  • Drinking unpasteurized milk

Brucellosis is rare in the United States. About 100 to 200 cases occur each year. Most cases are caused by the Brucella melitensis bacteria.

People working in jobs where they often come in contact with animals or meat are at higher risk. This includes slaughterhouse workers, farmers, and veterinarians.

Brucella is found in many countries worldwide including:

  • Egypt
  • Iraq
  • Iran
  • Jordan
  • Saudi Arabia
  • Chad
  • Greece
  • Mexico


Acute brucellosis may begin with mild flu-like symptoms, or symptoms such as:

  • Abdominal pain
  • Back pain
  • Fever and chills
  • Excessive sweating
  • Fatigue
  • Headache
  • Joint and muscle pain
  • Loss of appetite
  • Swollen glands
  • Weakness
  • Weight loss

High fever spikes often occur every afternoon. The name undulant fever is often used to describe this disease because the fever rises and falls in waves.

The illness may be chronic and last for years.

Exams and Tests

Your health care provider will examine you and ask about your symptoms. You'll also be asked if you've been in contact with animals or possibly eaten dairy products that were not pasteurized.

Tests that may be done include:


Antibiotics are used to treat the infection and prevent it from coming back. These include:

  • Doxycycline
  • Streptomycin
  • Gentamicin
  • Rifampin

Often, you need to take antibiotics for 6 weeks. If there are complications from brucellosis, you will likely need to take the medicines for a longer period.

Outlook (Prognosis)

Symptoms may come and go for years. Also, the illness can come back after a long period of not having symptoms.

Possible Complications

Health problems that may result from brucellosis include:

  • Bone and joint infection and damage
  • Encephalitis (swelling or inflammation of the brain)
  • Infective endocarditis (inflammation of the inside lining of the heart chambers and heart valves)
  • Meningitis (infection of the membranes covering the brain and spinal cord)

When to Contact a Medical Professional

Contact your provider for an appointment if:

  • You develop symptoms of brucellosis
  • Your symptoms get worse or do not improve with treatment
  • You develop new symptoms after treatment for brucellosis


Drinking and eating only pasteurized dairy products, such as milk and cheeses, is the most important way to reduce the risk for brucellosis. People who handle meat should wear protective eyewear and clothing and protect skin breaks from infection.

Detecting infected animals controls the infection at its source. Vaccination is available for cattle, but not humans.

Alternative Names

Cyprus fever; Undulant fever; Gibraltar fever; Malta fever; Mediterranean fever


Gotuzzo E, Ryan ET. Brucellosis. In: Ryan ET, Hill DR, Solomon T, Aronson NE, Endy TP, eds. Hunter's Tropical Medicine and Emerging Infectious Diseases. 10th ed. Philadelphia, PA: Elsevier; 2020:chap 75.

Gul HC, Erdem H. Brucellosis (Brucella species). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 226.

Review Date 8/26/2023

Updated by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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