IDWeek 2026 Study Examines 875 Brucellosis Diagnoses in US Hospital Admissions

Brucellosis was identified in approximately 0.6 cases per 100,000 hospital admissions in a retrospective analysis of US inpatient data presented at IDWeek in Washington, DC, from October 21 to 24. The study found differences in the odds of a brucellosis diagnosis across demographic groups and geographic regions, while leaving an important question unanswered: whether the infection is underdiagnosed in the US.

The abstract, “Human Brucellosis Infection in the United States,” reported 875 adults with a brucellosis discharge diagnosis among 147 million admissions from 2017 through 2020. Diagnoses were more likely among males and Hispanic patients, and the researchers identified higher odds in the South and West.

“It is unclear if Brucellosis is underdiagnosed in the United States,” the authors wrote. Their conclusion emphasizes obtaining a thorough exposure history and maintaining clinical suspicion when patients report contact with animals or consumption of unpasteurized milk products.

Examining National Inpatient Data

The researchers described brucellosis as a zoonotic infection transmitted through unpasteurized dairy products or occupational exposure to animals. Its nonspecific presentation can make diagnosis challenging, as can limitations in diagnostic testing. Limited recent US epidemiologic data prompted the investigation.

The retrospective cohort study used the National Inpatient Sample, which the abstract describes as the largest publicly available database of hospitalized patients in the US. Investigators included adults with a primary or secondary diagnosis of brucellosis and used demographic variables from the database in multivariable logistic regression analyses.

The reported prevalence reflects the number of brucellosis diagnoses among hospital admissions during the study period. It is not a population-based estimate of all US infections. The analysis focused on hospitalized adults, providing a view of diagnoses recorded in inpatient care.

Demographic Differences in Diagnosis

Among adults with a brucellosis discharge diagnosis, 62.9% were male and 37.1% were female. White patients represented 47.3%, Hispanic patients 34.7%, and Black patients 4.1%. Asian or Pacific Islander patients accounted for 3%, Native American patients for 1.2%, and patients categorized as other for 9.5%.

After adjustment, females had lower odds of a brucellosis diagnosis than males, with an adjusted odds ratio of 0.42 and a P value of less than 0.001. Black patients also had lower odds than White patients, with an adjusted odds ratio of 0.33 and a P value of less than 0.001.

Hispanic patients had higher odds than White patients, with an adjusted odds ratio of 3.70 and a P value of less than 0.001. The abstract also reported higher odds among Asian patients compared with White patients, with an adjusted odds ratio of 2.04 and a P value of 0.026.

Age was another factor associated with diagnosis. The researchers reported that brucellosis was most likely to be diagnosed among adults aged 45 to 64 years, with an adjusted odds ratio of 1.28 and a P value of 0.005. Adults aged 75 years and older were least likely to receive the diagnosis, with an adjusted odds ratio of 0.34 and a P value of less than 0.001.

Geographic and Hospital Patterns

Brucellosis diagnoses were significantly more likely in the South and West. The adjusted odds ratio was 1.74 for the South and 1.84 for the West, with P values of less than 0.001 for both regions. The supplied abstract does not specify the reference region used for these comparisons.

Hospital size also was associated with diagnosis. Patients in large hospitals had increased odds of being diagnosed with brucellosis compared with those in smaller hospitals, with an adjusted odds ratio of 1.3 and a P value of 0.004. The abstract does not establish why this difference occurred.

Exposure History Remains Central

The authors concluded that brucellosis is very rare in the US while identifying groups with higher odds of diagnosis in the inpatient data. Their findings describe associations; the abstract does not provide individual exposure histories explaining the demographic or geographic differences.

Despite uncertainty about underdiagnosis, the authors identified a practical opportunity for earlier recognition. “Good history taking and a high index of suspicion in patients with occupational exposure to animals and those who consume unpasteurized milk products may lead to earlier diagnosis,” they wrote. The study places that clinical message alongside national inpatient findings that help characterize where and among whom brucellosis diagnoses were recorded.

Poster authors: Armin Safdarpour, MD, MS; Chawki Harfouch, MD; Chukwuemeka Umeh, MD; Satvir Singh, MD; Pranav Barve, MD; Joanna Darlene Haw Young, MD; and Cory Wagner, MD.

Affiliations: KPC Hemet Global Medical Center and Loma Linda University Medical Center, California.

Source: IDWeek poster P-1557, “Human Brucellosis Infection in the United States.” Scheduled for October 23, 2026, in Poster Hall B-C.