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Brucellosis is a bacterial infection that causes disease in mammals, especially sheep, goats, and cattle. Humans become infected by exposure to the tissues, blood, urine, vaginal discharge, aborted fetuses, and placentas of infected animals. Contaminated animal products (e.g., raw milk and dairy products) can also transmit the disease.
Farmers, ranchers, and veterinarians, as well as slaughterhouse workers, meat inspectors, and laboratory personnel are at increased risk for brucellosis. In the United States, 100 to 200 brucellosis cases are reported each year. Most cases result from travel outside the United States and ingestion of unpasteurized milk products. Person-to-person transmission rarely has been documented. Because small amounts of aerosolized bacteria can cause disease, Brucella is considered a potential agent of bioterrorism.

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Resources for health care professionals


Purpose of surveillance:

  • To identify naturally occurring cases of brucellosis and common source outbreaks
  • To facilitate diagnosis of suspected cases and appropriate treatment when indicated
  • To identify other exposed persons requiring medical evaluation, monitoring and/or treatment
  • To identify and eliminate sources of transmission
  • To identify cases resulting from a bioterrorism attack

Brucellosis case data

Local epidemiology:

One confirmed and two probable brucellosis infections were reported in 2015, all in persons who likely acquired their infections while traveling internationally. Two of the cases required hospitalization. Because the infection can be acquired in the laboratory setting, nearly 40 clinical lab staff were monitored following exposure to one case's diagnostic specimen (a culture plate, that poses greater risk of transmission than antibody tests); no employees became infected.

Five other cases of brucellosis have been reported in King County over the past 10 years. Four cases were likely acquired during travel in India, and one case was reported in a recent immigrant from Africa. Each year in Washington state between zero and three cases of brucellosis are reported.