Scientists have estimated that the global incidence of Brucella infections is much higher than previously believed.

Findings suggest that at least 1.6 to 2.1 million new cases of human brucellosis occur every year. This differs significantly from one of the most cited references, which predicts an incidence of 500,000 new cases yearly.

Brucellosis is a bacterial disease that affects livestock and humans. In humans, the disease causes fever, sweats, fatigue, and malaise. People are normally exposed to Brucella by consuming unpasteurized milk products or handling contaminated animal tissues. Most human cases come from regions with highly dense at-risk populations.

The number of new human brucellosis cases annually remains unclear despite previous attempts to identify the impact of the disease, according to a study in the journal Emerging Infectious Diseases.

Risk by region
Researchers produced estimates using animal and human brucellosis data from the World Organization of Animal Health (WOAH) and human population data reported to the World Bank. Data was from 2014 to 2018. They used three statistical models and considered missing information. Disease misdiagnosis and under diagnosis were not considered in the models.

Because the team had more complete data for livestock than human disease, at both global and regional levels, they used livestock data as the basis to estimate disease incidence.

A total of 144 countries and 3.2 billion people were considered at risk. Models indicated Africa and Asia have most of the global risk and cases, although areas within the Americas and Europe remain of concern.

Countries not endemic for the disease record cases resulting from travel and trade of raw milk products across national borders.

“Among countries in Africa, inadequate or non-existent public and animal health programs perpetuate the status quo. This uncontrolled disease situation, accompanied by rapid population growth and increased demand for animal products, provides an unfortunate outlook for the future of brucellosis control across this entire region,” said researchers.

“Although risk is spread across the entire Asia region, the primary hotspot occurs in the Middle East. This increased risk is likely the result of having close contact with small ruminants and consuming their raw milk products.” 

French situation
Meanwhile, Santé publique France has revealed 40 cases of brucellosis were declared in 2022 in 12 regions. Of these, 38 were imported infections linked mainly to travel to Algeria but also to nations including Turkey, Tunisia, and Djibouti. One person fell sick after consuming a cheese from Lebanon.

For the two non-imported cases, one was a former slaughterhouse employee who started work before the elimination of brucellosis in farms. The other patient could not be contacted.

The number of cases returned to 2019 levels, in line with the resumption of travel to countries considered endemic, as COVID-19 pandemic restrictions were lifted. In 2020 and 2021, about 20 cases were recorded each year.

A total of 34 strains belonged to Brucella melitensis, one to Brucella abortus and another was not characterized. Symptom onset dates for cases reported in 2022 ranged from December 2018 to November 2022.

Fifteen cases were female. Patients were aged 5 to 91 with a median of 55 years old, including two children under 16 years old. Two cases were pregnant women.