It is, therefore, possible that some of the seropositive patients may have been exposed to Bartonella species other than B. quintana . Bartonella antibodies and may have been exposed to B. quintana . Multiple factors, including those related to disease transmission, host susceptibility, and ability to detect the organism, have likely contributed to the emergence of B. quintana infection among the homeless. Although these reports of B. quintana infection among homeless persons lack sufficient information to conclusively determine the disease vector, louse-borne infection remains a plausible hypothesis. Thus, it is possible that B. quintana infection is spread among homeless persons by as yet unidentified vectors or reservoirs.
Homeless persons are also at risk for non-vectorborne infectious diseases.
It is likely that factors such as crowding, altered immunity due to alcoholism or other co-existing health problems, and inadequate or infrequent access to medical care affect the transmission and spread of infectious diseases among the homeless. Although cases of B. quintana bacteremia among homeless persons have thus far been reported only from France and Seattle, Washington, the problem is probably not confined to these locations. To better define the geographic distribution and prevalence of B. quintana infection among homeless populations, a heightened awareness for this infection on the part of clinicians and the use of appropriate culture techniques by microbiology laboratories serving this population are needed. In addition, more specific serologic tests would aid in the diagnosis and assessment of the epidemiologic characteristics of B. quintana infections. The optimal treatment regimen for HIV-negative patients with suspected or confirmed B. quintana infection has not been established.