Q fever is an important worldwide zoonosis with nonspecific symptoms, making diagnosis challenging (1–3). Humans become infected mainly by inhalation of Coxiella burnetii–contaminated aerosols from animal waste or contaminated soil (4). C. burnetii is listed as a biologic weapon in the United States, and Q fever is a nationally notifiable disease in the United States, Australia, Netherlands, and Japan, but it is not a notifiable disease in China (2,5–7). Serologic epidemiology indicates that C. burnetii is widely distributed in China, but Q fever is rarely reported and might be neglected (2,7). We report a case of Q fever in a man in Shandong Province, China. The need for ethics approval and informed consent was waived, granted by the National Health Commission of China as part of outbreak investigation of infectious disease.

A 55-year-old man in a rural area of Jinan, Shandong Province, China, had fever (38.3 °C), headache, fatigue, loss of appetite, and myalgia develop on August 24, 2019 (Figure 1). He visited a local town hospital and was treated with acetaminophen and chlorpheniramine. When his symptoms persisted, he visited a county hospital on the 9th day after illness onset with a body temperature of 38.5°C and was treated with oral cefprozil and levofloxacin. On the 14th day of illness, with no improvement of his symptoms, he was transferred to a local municipal hospital. At admission, his body temperature was 39.0°C. Blood tests revealed elevation in neutrophil count and ratio, C-reactive protein, serum procalcitonin, and liver enzymes (Table). Bacterial culture showed no growth of microorganisms in either aerobic or anaerobic cultures (BD BACTEC FX 200 blood culture instrument, https://www.bd.com). We used PCR or immunologic test kits to test for viruses (influenza virus, severe fever with thrombocytopenia syndrome virus, Hantan virus, hepatitis B, hepatitis C, Epstein-Barr, and cytomegalovirus) and bacteria (Brucella, Mycobacterium tuberculosis, typhoid, and paratyphoid). We observed no positive results.

We sent samples to the CapitalBio MedLab in Beijing, China, where metagenomics next-generation sequencing (mNGS) was performed to determine the etiologic agent (Ion Proton Sequencer, https://www.thermofisher.com). A blood sample obtained from the patient provided DNA for that analysis (QIAamp MinElute ccfDNA Mini Kit; https://www.qiagen.com). On the 19th day after illness onset, the mNGS result revealed C. burnetii sequences in the patient’s blood sample; no other pathogens were observed. The sequence coverage rate of the C. burnetii genome was 97.66% (2,078,829 bp) with 137,272 reads (average length 141 bp, average quality 23), 1,105 contigs (range 262–16,242 bp), and an estimated 1.80 × 10⁴ copies/mL of C. burnetii in the sequencing sample. The mNGS result clearly indicated that the patient was infected with C. burnetii. Phylogenetic analysis revealed that the isocitrate dehydrogenase sequence from the patient formed a monophyletic group with sequences of C. burnetii from goats and from humans diagnosed with acute Q fever from GenBank (Figure 2). The isocitrate dehydrogenase sequence homology between the patient and those sequences were 99.85%–99.92%.

We performed cardiac ultrasound of the patient, which showed normal cardiopulmonary function and ruled out Q fever endocarditis. We treated the patient with oral doxycycline (100 mg 2×/d). His symptoms disappeared in 1 week, and he was discharged and continued on oral doxycycline (100 mg 2×/d) for 1 more week. We followed the patient for 1 year, noting no recurrence of Q fever.

This patient worked as a woodworker in a village without nearby abattoirs. He did not raise animals, but there were goats in his village, and mice were often observed around his living and working places. He denied any contact with domesticated or wild animals, ingestion of unpasteurized dairy products or uncooked meat, tick bite, exposure to similar patients, or any travel history to other places in China or abroad in the months before his illness.

Multiple factors likely delayed diagnosis of this patient with Q fever. Although nonspecific symptoms contributed, the greatest obstacles to diagnosis, we believe, were unawareness of the existence of Q fever by physicians and lack of conventional diagnostic reagents of Q fever, such as serologic and C. burnetii–specific PCR reagents, in the medical institutions our patient visited (8,9).

In conclusion, we report a patient with febrile illness from Shandong Province, China, without etiologic diagnosis and appropriate treatment for 3 weeks, until mNGS revealed C. burnetii genomic sequences in the patient’s blood. Our study suggests that physicians need to be more aware that Q fever is widespread in China and should be considered when diagnosing patients with persistent fever of unknown origin, even without clear exposure history. In addition, conventional diagnostic reagents of Q fever should be stored in local medical institutions in China. mNGS is a method to randomly sequence all nucleic acids and identify organisms by bioinformatics analysis in a sample, which is useful in identifying unknown pathogens. Our case supports previous studies that demonstrated that mNGS can be used to diagnose Q fever and other pathogens in humans (10).