Clinical characteristics of acute Q fever patients in South Korea and time from symptom onset to serologic diagnosis

Acute Q fever in patients with an influenza-like illness in regional New South Wales, Australia

INTRODUCTION

Query (Q) fever is a zoonosis caused by the bacterium Coxiella burnetii typically presenting as an influenza-like illness (ILI) with or without hepatitis. The infection may be missed by clinicians in settings of low endemicity, as the presentation is clinically not specific, and there are many more common differential diagnoses for ILI including SARS-CoV-2 infection.

METHODS

Residual serum samples were retrospectively tested for Phase 1 and 2 Q fever-specific IgM, IgG, IgA antibodies by indirect immunofluorescence and C. burnetii DNA by polymerase chain reaction. They had not been previously tested for Q fever, originating from undiagnosed patients with probable ILI, aged 10-70 years and living in regional New South Wales, Australia. The results were compared with contemperaneous data on acute Q fever diagnostic tests which had been performed based on clinicians requests from a geographically similar population.

RESULTS

Only one (0.2%) instance of missed acute Q fever was identified after testing samples from 542 eligible patients who had probable ILI between 2016-2023. Laboratory data showed that during the same period, 731 samples were tested for acute Q fever for clinician-initiated requests and of those 70 (9.6%) were positive. Probability of being diagnosed with Q fever after a clinician initiated request was similar regardless of the patients sex, age and the calendar year of sampling.

CONCLUSION

In this sample, Q fever was most likely to be diagnosed via clinician requested testing rather than by testing of undiagnosed patients with an influenza like illness.

Acute Coxiella burnetii Infection: A 10-Year Clinical Experience at a Tertiary Care Center in the United States

Background

Identifying and treating patients with acute Q fever who are at an increased risk of progressing to persistent disease is crucial for preventing future complications. In this study, we share our decade-long clinical experience with acute Q fever, highlighting the challenges that clinicians encounter from making an initial diagnosis and performing risk stratification to determining the appropriate prophylaxis regimen and duration.

Methods

We retrieved records of adult Mayo Clinic patients (≥18 years) with positive Coxiella burnetii serology results between 1 January 2012 and 31 March 2022. Patients with Q fever anti-phase II immunoglobulin G ≥1:256 by indirect immunofluorescence were further analyzed.

Results

Thirty-one patients were included. Their median age was 58 years (IQR, 50-64), and the majority were men (84%). Acute hepatitis (29%), flu-like illness (25.8%), and pneumonia (16%) were the most common presentations. Thirteen patients (42%) received antibiotic prophylaxis to prevent disease progression, with significant variation in the indications and duration across physicians. The combination of doxycycline and hydroxychloroquine was the preferred regimen. Prophylaxis was administered for a median 333 days (IQR, 168-414). Four patients (13%) progressed to Q fever native valve infective endocarditis, with elevated anticardiolipin immunoglobulin G levels being the sole risk factor in 2 cases. The small sample size precluded drawing conclusions on the impact of prophylaxis in preventing disease progression.

Conclusions

Management of acute Q fever is complicated by the lack of comprehensive clinical guidelines leading to varied clinical practices. There is a critical need for randomized trials to establish robust evidence-based protocols for management.

Current Status of Q Fever and the Challenge of Outbreak Preparedness in Korea: One Health Approach to Zoonoses

Human Q fever, a zoonosis caused by Coxiella burnetii, presents with diverse clinical manifestations ranging from mild self-limited febrile illnesses to life-threatening complications such as endocarditis or vascular infection. Although acute Q fever is a benign illness with a low mortality rate, a large-scale outbreak of Q fever in the Netherlands led to concerns about the possibility of blood transfusion-related transmission or obstetric complications in pregnant women. Furthermore, a small minority (< 5%) of patients with asymptomatic or symptomatic infection progress to chronic Q fever. Chronic Q fever is fatal in 5-50% of patients if left untreated. In South Korea, Q fever in humans was designated as a notifiable infectious disease in 2006, and the number of Q fever cases has increased sharply since 2015. Nonetheless, it is still considered a neglected and under-recognized infectious disease. In this review, recent trends of human and animal Q fever in South Korea, and public health concerns regarding Q fever outbreaks are reviewed, and we consider how a One Health approach could be applied as a preventive measure to prepare for zoonotic Q fever outbreaks.

Performance Evaluation and Validation of Air Samplers To Detect Aerosolized Coxiella burnetii

Coxiella burnetii, the etiological agent of Q fever, is an intracellular zoonotic pathogen transmitted via the respiratory route. Once released from infected animals, C. burnetii can travel long distances through air before infecting another host. As such, the ability to detect the presence of C. burnetii in air is important. In this study, three air samplers, AirPort MD8, BioSampler, and the Coriolis Micro, were assessed against a set of predetermined criteria in the presence of three different aerosolized C. burnetii concentrations. Two liquid collection media, phosphate-buffered saline (PBS) and alkaline polyethylene glycol (Alk PEG), were tested with devices requiring a collection liquid. Samples were tested by quantitative polymerase chain reaction assay (qPCR) targeting the single-copy com1 gene or multicopy insertion element IS1111. All air samplers performed well at detecting airborne C. burnetii across the range of concentrations tested. At high nebulized concentrations, AirPort MD8 showed higher, but variable, recovery probabilities. While the BioSampler and Coriolis Micro recovered C. burnetii at lower concentrations, the replicates were far more repeatable. At low and intermediate nebulized concentrations, results were comparable in the trials between air samplers, although the AirPort MD8 had consistently higher recovery probabilities. In this first study validating air samplers for their ability to detect aerosolized C. burnetii, we found that while all samplers performed well, not all samplers were equal. It is important that these results are further validated under field conditions. These findings will further inform efforts to detect airborne C. burnetii around known point sources of infection. IMPORTANCE Coxiella burnetii causes Q fever in humans and coxiellosis in animals. It is important to know if C. burnetii is present in the air around putative sources as it is transmitted via inhalation. This study assessed air samplers (AirPort MD8, BioSampler, and Coriolis Micro) for their efficacy in detecting C. burnetii. Our results show that all three devices could detect aerosolized bacteria effectively; however, at high concentrations the AirPort performed better than the other two devices, showing higher percent recovery. At intermediate and low concentrations AirPort detected at a level higher than or similar to that of other samplers. Quantification of samples was hindered by the limit of quantitation of the qPCR assay. Compared with the other two devices, the AirPort was easier to handle and clean in the field. Testing air around likely sources (e.g., farms, abattoirs, and livestock saleyards) using validated sampling devices will help better estimate the risk of Q fever to nearby communities.

Case Report: Metagenomic Next-Generation Sequencing Clinches the Diagnosis of Acute Q Fever and Verified by Indirect Immunofluorescence Assay

Q fever is a zoonotic infectious disease caused by Coxiella burnetii. The clinical symptoms of acute Q fever are usually atypical, and routine serological tests of C. burnetii are not readily available, making the diagnosis of Q fever a challenge. In this case, we report a male patient who had repeated fevers and was administered empirical anti-infective treatment, but the effect was poor. After conducting relevant laboratory and imagological examinations, the etiology has not yet been confirmed. Subsequently, metagenomic next-generation sequencing (mNGS) identified the sequence reads of C. burnetii from the patient's peripheral blood within 48 h, and then the diagnosis of acute Q fever was established. Moreover, the serological test of indirect immunofluorescence assay (IFA) of the C. burnetii antibody was further performed in the Centers for Disease Control, certifying the result of mNGS. The patient was ultimately treated with doxycycline and recovered well. mNGS is an unbiased and comprehensive method in infrequent or culture-negative pathogen identification. To our knowledge, this is the first case of acute Q fever identified by mNGS and confirmed by IFA in Taizhou, China. A further large-scale prospective clinical cohort study is worth carrying out to compare the diagnostic efficiency of mNGS with traditional serological methods and PCR in acute Q fever.

Shedding and extensive and prolonged environmental contamination of goat farms of Q fever patients by Coxiella burnetii

BACKGROUND

A majority (>70%) of Q fever patients in South Korea do not have a history of animal contact. Therefore, unconscious environmental exposure is suspected. The aim of this study was to investigate exposure of Q fever patients to environmental contamination and animal shedding.

METHODS

Two goat farmers were enrolled. One was diagnosed with Q fever 3 years ago (Farm 1). Among 20 goats on Farm 1, five were tested randomly and found to be Q fever PCR-positive. Three of the five were Q fever ELISA-positive. Two of five environmental samples taken in 2015 were PCR-positive. In 2018, 17 of 18 environmental samples were PCR-positive. On Farm 2, 54 of the 77 goats were PCR-positive, and 63 were ELISA-positive. Twelve of 14 environmental samples were PCR-positive. Repeat administration of oxytetracycline to goats led to a gradual reduction in PCR-positive tests over a 5-month period. However, PCR-positivity of the farm environment persisted for 5 months.

CONCLUSION

The environment on farms owned by Q fever patients was contaminated extensively and persistently, even after antibiotic treatment of goats and environmental decontamination. Undetected environmental contamination can be a major source of sporadic Q fever infection in South Korea.

Seroreactivity to Coxiella burnetii in an Agricultural Population and Prevalence of Coxiella burnetii Infection in Ticks of a Non-Endemic Region for Q Fever in South Korea

Coxiella burnetii infects humans and wild and domesticated animals. Although reported cases on Jeju Island, off the coast of South Korea, are rare, the region is considered to have a high potential for Q fever. We investigated the seroprevalence of antibodies to C. burnetii in 230 farmers living in ten rural areas on Jeju Island between January 2015 and December 2019. Blood samples were collected and examined for C. burnetii Phase I/II IgM and IgG antibodies. Trained researchers collected ticks from rural areas. Clone XCP-1 16S ribosomal RNA gene sequencing was performed to identify Coxiella species from the collected ticks. The overall seroprevalence of antibodies to C. burnetii in farmers was 35.7%. The seroprevalence was significantly higher in fruit farmers. Of the collected ticks, 5.4% (19/351) of the Haemaphysalis longicornis ticks harbored C. burnetti. A high seroprevalence of antibodies to C. burnetii was observed in this region of Jeju Island, confirming that C. burnetti is endemic. Physicians should thus consider Q fever in the differential diagnosis of patients that present with acute fever after participating in outdoor activities.

Epidemiological investigation and physician awareness regarding the diagnosis and management of Q fever in South Korea, 2011 to 2017

BACKGROUND

In South Korea, the number of Q fever cases has rapidly increased since 2015. Therefore, this study aimed to characterize the epidemiological and clinical features of Q fever in South Korea between 2011 and 2017.

METHODS/PRINCIPAL FINDINGS

We analyzed the epidemiological investigations and reviewed the medical records from all hospitals that had reported at least one case of Q fever from 2011 to 2017. We also conducted an online survey to investigate physicians' awareness regarding how to appropriately diagnose and manage Q fever. The nationwide incidence rate of Q fever was annually 0.07 cases per 100,000 persons. However, there has been a sharp increase in its incidence, reaching up to 0.19 cases per 100,000 persons in 2017. Q fever sporadically occurred across the country, with the highest incidences in Chungbuk (0.53 cases per 100,000 persons per year) and Chungnam (0.27 cases per 100,000 persons per year) areas. Patients with acute Q fever primarily presented with mild illnesses such as hepatitis (64.5%) and isolated febrile illness (24.0%), whereas those with chronic Q fever were likely to undergo surgery (41.2%) and had a high mortality rate (23.5%). Follow-up for 6 months after acute Q fever was performed by 24.0% of the physician respondents, and only 22.3% of them reported that clinical and serological evaluations were required after acute Q fever diagnosis.

CONCLUSIONS

Q fever is becoming an endemic disease in the midwestern area of South Korea. Given the clinical severity and mortality of chronic Q fever, physicians should be made aware of appropriate diagnosis and management strategies for Q fever.

Isolation of Coxiella burnetii in patients with nonspecific febrile illness in South Korea

Background

The number of human Q fever cases in South Korea has been rapidly increasing since 2015. We report the first isolation of Coxiella burnetii in Korea in two patients who initially presented with non-specific febrile illness and were finally diagnosed with acute Q fever in South Korea.

Case presentation

Two adult patients with fever had serologic tests against C. burnetii initially negative, and polymerase chain reaction against 16S rRNA using whole blood was also negative. After bacterial amplification of C. burnetii in immune-depressed mice, we isolated C. burnetii from patients with acute Q fever. The isolates KZQ2 and KZQ3 were confirmed by polymerase chain reaction, nucleotide sequence analysis, and morphologic observation using a transmission electron microscope.

Conclusions

These results can help us understand the clinical and epidemiologic features of Q fever in South Korea.