Q fever: an under-reported reportable communicable disease

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Public Health Surveillance

Background:

• Q fever is a significant zoonotic disease caused by Coxiella burnetii.
• Accurate incidence data are crucial for public health response and resource allocation.
• Existing Q fever surveillance relies on reported cases, which may not reflect true prevalence.

Purpose of the Study:

• To provide real-world clinical laboratory data on Q fever incidence.
• To compare clinical laboratory findings with Centers for Disease Control and Prevention (CDC) reporting.
• To assess potential underestimation of Q fever by current surveillance methods.

Main Methods:

• Analysis of Coxiella burnetii IgG antibody titres from specimens submitted to a large US clinical laboratory (2010-2016).
• Definition of presumptive acute Q fever (phase II IgG titre ≥1:128, phase I titre <1:1024).
• Definition of presumptive chronic Q fever (phase I IgG titre ≥1:1024) based on single serum specimen results.

Main Results:

• An average of 328 presumptive acute Q fever cases were identified annually in the clinical laboratory data.
• This number is nearly three times the annual average of 122 cases reported to the CDC.
• The number of identified chronic Q fever cases (34 annually) was similar to CDC reports (29 annually).

Conclusions:

• Clinical laboratory data suggest a higher incidence of acute Q fever than officially reported.
• Current CDC surveillance may significantly underestimate the true incidence of acute Q fever.
• Real-world laboratory data are essential for a comprehensive understanding of Q fever epidemiology.