Alternative names
Rock fever; Cyprus fever; Undulant fever; Gibraltar fever; Malta fever

Brucellosis is a disease caused by contact with animals carrying the Brucella bacteria.

Causes, incidence, and risk factors

Brucella bacteria infect cattle, goats, camels, dogs, and pigs. Transmission of the disease to humans occurs by contact with infected meat, placenta of infected animals, or ingestion of unpasteurized milk or cheese.

The illness may be chronic and persist for years. Brucellosis is rare in the United States, except in the western states and in visitors or immigrants from countries where it is prevalent (Spain, Mexico, South America, Middle East).

Approximately 100 to 200 cases occur in the United States each year. People working in occupations requiring frequent contact with animals or meat, such as slaughterhouse workers, farmers, and veterinarians, are at high risk.

Acute brucellosis may begin with mild flu-like symptoms or with fever, chills, sweating, muscle aches (myalgia), joint aches (arthralgia), and malaise. Classically, fever spikes occur every afternoon to levels around 104 degrees Farenheit. “Undulant” fever derives its name from this undulating or up-and-down fever.


  • Fever  
  • Chills  
  • Sweating, excessive  
  • Weakness  
  • Weight loss  
  • Fatigue  
  • Headache  
  • Abdominal pain  
  • Enlarged liver  
  • Back pain  
  • Loss of appetite  
  • Joint pain

Additional symptoms that may be associated with this disease:

  • Muscle pain  
  • Glands, swollen

Signs and tests

  • Blood culture  
  • Urine culture (clean catch)  
  • CSF culture  
  • Bone marrow culture  
  • Serology detecting brucellosis antigen

This disease may also alter the results of the following tests:

  • Quantitative immunoglobulins (nephelometry)  
  • Immunoelectrophoresis - serum  
  • Febrile/cold agglutinins


A combination antibiotic therapy, such as doxycycline and rifampin or an aminoglycoside, is recommended to treat and prevent relapse of infection. Longer courses of therapy may be required for complications.

Note: Doxycycline is usually not prescribed for children until after all the permanent teeth have come in because it can permanently discolor the teeth that are still forming.

Expectations (prognosis)

Relapse may occur, and symptoms may persist for years. Reactivation can occur after a long period of time, similar to tuberculosis.


  • Bone and joint lesions  
  • Infective endocarditis  
  • Encephalitis  
  • Meningitis  
  • Chronic fatigue syndrome

Calling your health care provider

Call for an appointment with your health care provider if symptoms of brucellosis develop.

Also call if symptoms worsen or do not improve with treatment or if new symptoms develop.


Pasteurization of milk and eating only pasteurized cheeses are the most important preventative measures. People who handle meat should wear protective glasses 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.

Johns Hopkins patient information

Last revised: December 6, 2012
by Simon D. Mitin, M.D.

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