A Case of Brucellosis Concomitant with Severe Fever with Thrombocytopenia Syndrome — Weifang City, Shandong Province, China, 2023

A 52-year-old female was referred to Yidu Central Hospital of Weifang presenting with fever, generalized muscle and joint pain, chills, severe fatigue, and diminished appetite. The patient, a farmer resident in Changle County, Weifang City, Shandong Province, reported extensive contact with sheep and other livestock.

On July 17, 2023, the patient developed a fever, registering a temperature of 38.9 ℃. Despite receiving treatment at a local hospital for three days, her temperature continued to fluctuate. She reported experiencing a worsening of symptoms.

On July 26, 2023, a patient presented at Yidu Central Hospital of Weifang for evaluation; initial blood tests conducted prior to admission indicated leukopenia. She was assessed in the outpatient clinic with a primary diagnosis of unexplained fever. The findings from the physical examination at the time of admission included a temperature of 38.5 °C, a respiratory rate of 22 breaths per minute, a pulse rate of 86 beats per minute, and a blood pressure of 123/78 mmHg. The patient was alert but appeared lethargic and was minimally responsive. Examination revealed slight yellowing of the skin and sclera, with no accompanying rash. A tender lymph node approximately the size of a peanut was palpable in the right groin. Examination of the heart and lungs did not disclose any significant abnormalities. Laboratory tests showed decreased leukocyte and platelet counts, while elevations were noted in ferritin, procalcitonin, C-reactive protein, and interleukin-6 levels (Table 1). The Rose Bengal test for Brucella and the serum agglutination test at a titer of 1∶200 were both positive, confirming an infection with Brucella. Antibiotic therapy was subsequently initiated.

On July 27, 2023, the patient exhibited a significant drop in platelet count to 80×10⁹/L. Although renal function, blood glucose, and lipid levels remained within normal limits, elevated levels were noted in several liver function markers — including alanine aminotransferase, aspartate aminotransferase, total bile acids, alkaline phosphatase, lactate dehydrogenase — as well as in creatine kinase and its isoenzymes (Table 1). Electrolyte concentrations were overall stable, with the exception of a decreased sodium level (Table 1). Imaging using superficial lymph node B-ultrasound identified a lymph node measuring 2cm by 1cm with distinct borders in the right groin. Further laboratory analysis using RT-PCR detected SFTSV nucleic acids in the serum at a concentration of 5.52×10⁴ copies/mL. Based on these clinical findings and laboratory data, the patient was diagnosed with SFTS and subsequently received symptomatic treatment.

On July 28, 2023, the patient’s blood culture tested positive for Brucella melitensis biovar 3, confirming an infection with brucellosis.

On August 1, 2023, the patient’s condition and laboratory indicators stabilized. By August 3, 2023, the patient was discharged following the resolution of her symptoms and the normalization of all laboratory test indicators.

Following a series of diagnostic tests, the patient was confirmed to have SFTS and brucellosis on the tenth day after disease onset and was subsequently discharged on the seventeenth day. Treatment initiated post-diagnosis included rest, doxycycline (100 mg twice daily) and levofloxacin (500 mg once daily) for brucellosis, along with caffeic acid (0.2 g three times daily) to boost white blood cells and platelet counts. Nutritional support was provided through supplements of vitamin C and vitamin B6. No similar cases were identified upon interviewing her family, neighboring villagers, and the hospital staff involved in her care.

In this study of co-infection, we examined patients diagnosed with two distinct diseases at Yidu Central Hospital of Weifang in 2023. The analysis included 75 cases of brucellosis and 26 cases of SFTS. Both the incidence and distribution of these infectious diseases exhibited temporal and spatial overlap. Brucellosis cases occurred throughout the year, peaking between January and July, whereas SFTS cases were confined to the months of May through October, as shown in Figure 1. Geographically, brucellosis cases were more broadly spread, with the majority (72%) originating from Linqu County and Qingzhou county-level City, Weifang City. In contrast, all reported cases of SFTS were from these same locations.