There has been ongoing concern and studies about the health and wellness of the older homeless population, typically ages 50 to 64 and older, as to whether they are significantly more sickly than their younger counterparts, and if they are under-served.A 2011 study led by Dr. Rebecca T. Brown in Boston, conducted by the Institute for Aging Research (an affiliate of Harvard Medical School), Beth Israel Deaconess Medical Center, and the Boston Health Care for the Homeless Program found the elderly homeless population had "higher rates of geriatric syndromes, including functional decline, falls, frailty, and depression than seniors in the general population, and that many of these conditions may be easily treated if detected". The report was published in the Journal of Geriatric Internal Medicine. There are government avenues which provide resources for the development of healthcare for homeless people. In the United States, the Bureau of Primary Health Care has a program that provides grants to fund the delivery of healthcare to homeless people. According to 2011 UDS, data community health centers were able to provide service to 1,087,431 homeless individuals. There are also many nonprofit and religious organizations which provide healthcare services to homeless people. These organizations help meet the large need which exists for expanding healthcare for homeless people. There have been significant numbers of unsheltered persons dying of hypothermia, adding impetus to the trend of establishing warming centers, as well as extending enumeration surveys with vulnerability indexes.
Carrión developed the disease three weeks after the inoculation and kept a meticulous record of clinical symptoms and signs until the disease rendered him incapable of the task and he died at age 28 several weeks later—October 5, 1885. Carrión proved that Oroya fever and verruga peruana were two stages of the same disease, and not two different diseases as was thought at the time. His work did not result in a cure immediately, but his research started the process. Peru has named October 5 as "Peruvian Medicine Day" in his honor.Peruvian microbiologist Alberto Barton discovered the causative bacterium in 1905, but his results were not published until 1909. Barton originally identified them as "endoglobular" structures, bacteria living inside red blood cells. Until 1993, the genus Bartonella, within the family Bartonellaceae, contained only one species; 23 are now identified. CSD
In 1988, English et al. isolated and cultured a bacterium that was named Afipia felis in 1992 after the team at the Armed Forces Institute of Pathology that discovered it. This agent was considered the cause of cat-scratch Disease (CSD) but further studies failed to support this conclusion. Serologic studies associated CSD with Bartonella henselae, reported in 1992. In 1993, Dolan  isolated Rochalimae henselae (now called Bartonella henselae) from lymph nodes of patients with CSD. Bartonella spp. are commonly treated with antibiotics including azithromycin, based on a single small randomized clinical trial. Treatment may take up to one year to eliminate the disease. CSD often resolves spontaneously without treatment.