Appendix A: Q Fever Key Point Summaries
Acute Clinical Features
- Prolonged fever (>10 days) with a normal leukocyte count, thrombocytopenia, and increased liver enzymes is suggestive of acute Q fever infection.
- Children with Q fever generally have a milder acute illness than adults.
- Children are more likely to have a rash than adults. Rash has been reported in up to 50% of children with acute Q fever.
- Women infected with Q fever during pregnancy are at increased risk for miscarriage and preterm delivery.
- Women of child-bearing age who receive a diagnosis of Q fever can benefit from pregnancy screening and counseling to guide health-care management decisions.
Chronic Clinical Features
- Persons who are at high risk for development of chronic Q fever include persons with preexisting valvular heart disease, vascular grafts, or arterial aneurysms.
- Infection during pregnancy and immunosuppression (e.g., from chemotherapy) are both conditions that have been linked to chronic Q fever development.
- Endocarditis and infections of aneurysms or vascular prostheses are the most common forms of chronic Q fever and generally are fatal if untreated.
- Chronic Q fever is rarely reported in children.
- In contrast with adults, osteomyelitis is one of the most common findings in children with chronic Q fever.
- Polymerase chain reaction (PCR) of whole blood or serum provides rapid results and can be used to diagnose acute Q fever in approximately the first 2 weeks after symptom onset but before antibiotic administration.
- A fourfold increase in phase II immunoglobulin G (IgG) antibody titer by immunofluorescent assay (IFA) of paired acute and convalescent specimens is the diagnostic gold standard to confirm diagnosis of acute Q fever. A negative acute titer does not rule out Q fever because an IFA is negative during the first stages of acute illness. Most patients seroconvert by the third week of illness.
- A single convalescent sample can be tested using IFA in patients past the acute stage of illness; however, a demonstrated fourfold rise between acute and convalescent samples has much higher sensitivity and specificity than a single elevated, convalescent titer.
- Diagnosis of chronic Q fever requires demonstration of an increased phase I IgG antibody (≥1:1024) and an identifiable persistent infection (e.g., endocarditis)
- PCR, immunohistochemistry, or culture of affected tissue can provide definitive confirmation of infection by Coxiella burnetii.
- Test specimens can be referred to CDC through state public health laboratories.
Treatment and Management
- Because of the delay in seroconversion often necessary to confirm diagnosis, antibiotic treatment should never be withheld pending laboratory tests or discontinued on the basis of a negative acute specimen. In contrast, treatment of chronic Q fever should be initiated only after diagnostic confirmation.
- Treatment for acute or chronic Q fever should only be given in clinically compatible cases and not based on elevated serologic titers alone (see Pregnancy section for exception).
- Doxycycline is the drug of choice, and 2 weeks of treatment is recommended for adults, children aged ≥8 years, and for severe infections in patients of any age.
- Children aged <8 years with uncomplicated illness may be treated with trimethoprim/sulfamethoxazole or a shorter duration (5 days) of doxycycline.
- Women who are pregnant when acute Q fever is diagnosed should be treated with trimethoprim/sulfamethoxazole throughout the duration of pregnancy.
- Serologic monitoring is recommended following acute Q fever infection to assess possible progression to chronic infection. The recommended schedule for monitoring is based on the patient's risk for chronic infection.
- The majority of occupationally related Q fever outbreaks in the United States have occurred among biomedical research facility workers exposed to infected pregnant ewes
- Workplaces with employees at high risk for C. burnetii exposure (e.g., laboratories that experiment with C. burnetii and animal research facilities) should institute a Q fever medical surveillance and health education monitoring program. Engineering controls, administrative controls, and use of personal protective equipment are recommended when appropriate.
- Use of standard precautions by health-care providers is sufficient to prevent Q fever transmission during routine care. Additional precautions should be used during aerosol-generating procedures.
- Use of postexposure prophylaxis is not recommended for workers after a known or potential exposure; any acute febrile illness that occurs within 6 weeks of exposure warrants immediate treatment and medical evaluation.
Surveillance and Reporting
- Human Q fever infection is a notifiable disease in the United States.
- Health-care providers who identify a potential case of Q fever should notify the local/state health department, which can assist with diagnostic testing.
- Surveillance and reporting of Q fever are key components of public health education and disease prevention efforts.
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