Diagnosis and treatment of Q fever: Attempts to clarify current problems in Japan

"Q fever" is a generic term for infection caused, mostly in the form of pneumonia or bronchitis, by Coxiella burnetii (Q-fever Coxiella), a pathogen closely related to Rickettsia and Legionella. Q fever is an influenza-like, transient febrile infectious disease that is common to humans and animals; it develops after the transmission of the infectious agent from livestock or pet animals, but person-toperson transmission is rare. In Europe and the United States, it is ranked fourth or fifth as an underlying cause of community-acquired pneumonia. Many patients with Q fever have a good prognosis, and their mortality is about 1%-2% when left untreated. However, because some patients may take a long time to be cured or may have a chronic condition with poor prognosis, patients with definitely diagnosed Q fever or those strongly suspected of having Q fever are strongly recommended to receive treatment. The definite diagnosis of Q fever is made based on a significant increase in serum antibody titers, the determination of which often requires considerable time, and therefore patients must be monitored for a certain period. Q-fever Coxiella, an obligate intracellular parasite, is basically not susceptible to β-lactam antibiotics, which barely permeate into the cells, but the parasite is susceptible to tetracyclines, macrolides, and quinolones, with these agents being sufficiently permeable into the cells. However, there are many cases of spontaneous cure, and it is likely that β-lactam treatment may have been involved in these cases. Vaccination against Q fever is not common in Japan.