The risk for HIV infection is higher in the following populations of homeless people: those engaged in sexual behavior such as sex work, receptive anal sex, and having multiple sexual partners; those who find it more difficult to use or obtain condoms (6,10); and those who use drugs in shooting galleries or who share syringes or other drug paraphernalia (6). Controlling the spread of HIV among the homeless requires interventions targeting high-risk groups such as youth, female street sex workers, and IDUs (16,19,20). For example, an intensive intervention program targeting homeless youth achieved a significant reduction of unprotected sex acts over 12 months (p = 0.018) and drug use over 12 months (p = 0.019) among female participants as well as a strong reduction in marijuana use over 12 months (p = 0.082) in male participants (16). The program involved training shelter staff and residents in small groups, providing access to health resources, and making condoms available easily and at no cost. An intervention program targeting homeless and crack-using African American women provided them with psychoeducational information and skills training on how to reduce HIV risk and drug use; the program significantly (p = 0.03) reduced the number of unprotected sex acts among participants, compared with control participants, at 6 months after the program was started (19). In Rhode Island, a prescription program to deliver syringes to high-risk underserved and diverse populations was conducted within the context of comprehensive drug treatment. The program recruited 327 persons and found that 86% saw a physician for syringe prescription at least 1 time, 46% at least twice, and 32% >3 times; this program demonstrated the feasibility and acceptability of such a program for and by its target population, and it reduced the number of injection drug–related risky behavior traits (20).

Factors predisposing to infections with HBV and HCV are much the same as those for HIV, with HBV a greater risk with of unprotected sex and HCV a greater risk with injection drug–related behavior (9,10). Therefore, intervention measures to prevent the spread of HCV among the homeless are the same as those noted above for HIV prevention (16,19,20). As for HBV infection, some evidence suggests that HBV immunizations for the homeless are feasible and effective. A study in New Haven, Connecticut, recruited 212 IDUs at syringe-exchange sites to undergo HBV vaccination. Most (63%) were vaccine eligible, including 23% of homeless persons; of the vaccine-eligible IDUs, 77% completed 2 vaccinations and 66% completed all 3 vaccinations (21). Homeless IDUs were more likely than other IDUs to complete the vaccination schedule, probably because the vaccination program and the syringe-exchange sites are areas where the homeless tend to congregate, providing more opportunities for them to access these services. An accelerated HBV vaccination schedule should be the regime of choice for homeless people, especially those with a past history of drug use. This recommendation is supported by a study in the United Kingdom that compared completion rates for a conventional HBV vaccine schedule (immunization at 0, 1, and 6 months) conducted among homeless in 1999 with the rates for an accelerated immunization schedule (immunization at 0, 7, and 21 days) in 2000. The completion rates for the accelerated vaccination regimen were almost 7 times higher than rates for the conventional one (22). A hepatitis A (HAV) outbreak has been reported among homeless persons and IDUs in Bristol (UK), possibly transmitted parenterally (8). The same city is the site of a successful HAV vaccination program for homeless persons and drug users to control HAV outbreaks and prevent transmission to the wider population (8). In June 2000, this program immunized 136 homeless persons and IDUs and 9 members of staff in shelters, hostels, drug services, and drop-in centers. The result was a significant (p<0.001) drop in HAV cases in the Bristol population (including homeless persons) from 90 cases (January–June) to 33 (July–December) (8).

Figure

Figure. . . An intervention in a homeless shelter in Marseilles for infectious diseases survey.

Yearly snapshot interventions in shelters, performed by large multidisciplinary teams, have been reported to be efficient for controlling or preventing infections among the homeless (5,11). These investigations can reach a category of homeless who do not usually seek healthcare. In Marseilles, since 2000, a large mobile team is sent once a year to perform these snapshot interventions in order to survey louse-borne disease in the 2 shelters designated for accommodating the homeless (5). This team comprises 30–40 persons, including physicians, residents, or fellows; nurses; and outreach workers. During interventions, homeless persons who choose to participate are interviewed and physically examined. Clothes are carefully screened for body lice, and specific treatment is given when appropriate. Nurses also collect blood and other microbiologic samples for serologic tests for louse-, flea-, and tick-borne diseases, as well as hepatitis, HIV; and syphilis. Arthropods are collected and PCR-screened for pathogens such as Bartonella, the epidemic typhus rickettsia, and Borrelia recurrentis. Depending on the epidemiologic situation, other surveys such as for the prevalence of TB and other respiratory diseases can be organized (27). In such cases, a pneumologist and radiography technologists using a mobile x-ray machine are added to the intervention team. These snapshot interventions led to successively identifying a high prevalence of louse infestation, louse-borne diseases such as B. quintana infection, and skin infections among this homeless population (5,11). Snapshot interventions have also identified the risk for the homeless of acquiring other louse-borne diseases such as epidemic typhus and relapsing fever, and enabled the first isolation of A. baumanii from lice (5,32,39). This strategy of wide systematic testing of infectious diseases in this population also led to the unexpected discovery of an outbreak of acute Q fever in a homeless shelter in Marseille (40). Epidemiologic investigations of this outbreak showed that exposure to wind from an abandoned slaughterhouse, used for an annual Muslim sheep feast, was the main risk factor for developing Coxiella burnetii infection (Figure).

Evidence suggests that appropriate public health interventions can be effective in preventing and controlling the spread of numerous transmitted diseases among homeless persons, which is a public health concern both for the homeless and the larger population. These interventions should be tailored to the targeted populations and focused on areas where the homeless are more likely to reside. The strategies reported to be efficient include tailored education; distribution of free condoms; implementation of a syringe and needles prescription program for HIV and HCV; systematic chest radiography for TB screening in shelters and DOT for TB; improvement of personal, clothing, and bedding hygiene; use of ivermectin to treat pruritus most often caused by scabies or body louse infestation; and immunizations against HBV, HAV, influenza, Streptococcus pneumoniae, and diphtheria. Implementation of systematic vaccination schedules to prevent communicable diseases in the homeless is a major public health priority. The success of these interventions requires the implementation of a national public health prevention program for the homeless. A yearly snapshot intervention is 1 means to achieve these objectives.