Brucellosis is a chronic zoonotic infection caused by bacteria of the genus Brucella, which is widespread worldwide. At least four species of bacteria in the genus Brucella are capable of causing human infections, including Brucella abortus, Brucella melitensis, Brucella suis, and Brucella canis, of which Brucella abortus is one of the most important pathogens causing human brucellosis¹. Brucella is a highly contagious gram-negative bacterium that can invade human lymph nodes and reproduce to form foci through various means, such as the digestive tract, respiratory tract, and contact transmission². The bacteria can also rupture cells and spread through the blood, staying in the lymph nodes, liver, spleen, bone marrow, and other organs. This can lead to the appearance of multiple foci and often involves multiple organs². The clinical manifestations of brucellosis are fever, malaise, joint and muscle pain, and in severe cases, death³. It is estimated that brucellosis epidemics occur in more than 170 countries or regions around the world, with nearly 500,000 or more new cases worldwide each year, which not only affects local economic development but also poses a serious threat to people’s lives and health^4,5.

The primary transmission routes of brucellosis to humans are through direct contact with infected animals or consumption of contaminated animal products, such as unpasteurized milk and dairy products, and undercooked meat^1,5. Additionally, occupational exposure, such as handling infected animals or their tissues, is a significant risk factor for human infection⁵. While human-to-human transmission is rare and remains controversial, it has been reported in a few cases through routes such as the placenta, lactation, sexual contact, and blood transfusion⁶. However, these modes of transmission are considered exceptional and not the primary sources of infection in the general population. Several studies have confirmed the risk of transmission of brucellosis by blood transfusion in several cases. In two cases found in the literature, the transfusions occurred in the same hospital ward where two thalassemia patients received regular blood transfusions; both received blood transfusions from the same donor, a farmer who reared cattle and sheep⁷. In the other case, the recipient started showing clinical symptoms one month after the transfusion. The donor began to show clinical symptoms after donation and was tested for intra-blood agglutination of Mycobacterium abortus at a titer of 1:1280; considering the diagnostic level of the history and the titer four weeks after donation, the donor’s blood was likely to show bacteremia at that time⁸.

Reducing the risk of transfusion-transmitted diseases is a concern for the blood transfusion industry, the healthcare industry as a whole, and society as a whole. The U.S. Food and Drug Administration (FDA), in order to reduce the risk of blood transfusion, has emphasized that pre-donation health inquiries should be made of potentially infected brucellosis patients⁸. However, in most of the brucellosis-endemic regions of the world, the investigation of blood donors for brucellosis infection is not yet complete and widespread. As China’s national standard that stipulates the health examination items and criteria that blood donors need to undergo before donating blood, China’s Requirements for Health Examination of Blood Donors (GB18467-2011) stipulates that people who have not recovered from brucellosis for two years should not donate blood temporarily, but brucella testing has not yet been included in the blood screening programme for blood donors. With the rise of brucellosis infection rate, the pathogenesis, vaccination and complication treatment of brucellosis have received more attention from researchers, and the risk of brucellosis transfusion transmission has been a neglected area. Many blood station employees and healthcare professionals who collect blood may not be fully aware of all the traits of Brucella that can be transmitted through blood transfusions, as well as the extent to which transfusion transmission has been studied in clinical settings.

At present, the investigation of Brucella infection in blood donors has not been formally carried out in Brucellosis-endemic areas in northern China⁹. Therefore, preventive and control measures for blood safety in brucellosis-endemic areas are necessary.

The risk of brucellosis infection in recipients or the occurrence of adverse reactions to blood transfusion increases when Brucella-positive donors conceal their epidemiological history or lack a clear clinical picture when participating in blood donation activities. This is due to the fact that blood products are kept at low temperatures in blood centers, and Brucella can live for up to six months at 4 °C when there is no appropriate culture media present. People who have had brucellosis in the past have been documented to have donated blood in earlier investigations. Blood stored in Mexican blood centers tested positive for Brucella antibodies in up to 3.6% of cases, and in areas where brucellosis is endemic, about 20% of patients are undiagnosed, thus posing a serious threat to blood safety in areas where brucellosis is endemic. At the same time, once infected, Brucella can not be completely eliminated by the host¹⁰, the human body to Brucella infection-specific antibodies may persist for a long time, and there is a risk of carrying Brucella¹¹, so the blood donor population with a history of previous infectious diseases also need to pay close attention.

In clinical practice, the diagnosis of brucellosis is mainly based on serological tests, specifically, plate agglutination test, tiger red plate agglutination test, tube agglutination test, and so on are more common laboratory tests, in addition, the use of antiglobulin test, complement binding test and so on can effectively detect brucellosis¹². Additionally, the use of the antiglobulin test (Coombs test) and complement binding test (CFT) can effectively detect brucellosis¹². Although the gold standard for the diagnosis of Brucella infection is the isolation and culture of Brucella from blood, tissue fluids, or tissue samples^13,14, serological agglutination test results are not the best conclusive evidence for the diagnosis of Brucella infection, but the serological agglutination test screening is still necessary. To guarantee the safety of blood, blood donors who test positive for Brucella must be removed, especially if they are still in the incubation stage of the illness.

Given the increasing prevalence of the illness, we should be more rigorous in our efforts to prevent and control brucellosis in endemic areas. Blood safety standards require Brucella screening of blood donors in endemic areas. To reduce the risk of transfusion-transmitted brucellosis and inform blood safety practices in endemic areas, the purpose of this study was to further investigate the necessity of starting Brucella serological testing in the blood donor population in endemic areas through a meta-analysis of the detection rate of Brucella serology positivity in humans in endemic areas.