This outbreak investigation identified evidence of both HBV and HIV transmission among residents with severe mental illness at a LTCF. Although a high prevalence of HBV and HIV infections has been documented among severely mentally ill persons 
, our investigation suggests this population remains at risk for newly acquiring these infections even while receiving care within a LTCF setting. Although this investigation was not able to demonstrate the mode of HBV and HIV transmission, it highlighted several strategies (such as routine screening for bloodborne pathogens 
, HBV vaccination, access to condoms, and risk-reduction education) which could prevent the spread of these infections among mentally ill residents of LTCFs.
Overall 8 residents were diagnosed with acute HBV infection and 3 residents were diagnosed with chronic HBV infection. Although these residents were diagnosed at different phases of their infection (acute vs. chronic), these infections may have all been acquired during their stay in the facility. This is supported by the finding that viruses obtained from 2 residents with chronic HBV infections were closely related to viruses obtained from 4 residents with acute HBV infections. This suggests that all residents with available complete HBV genome sequences likely belonged to a single transmission network. One of the residents with chronic HBV infection may have served as a reservoir for HBV transmission within LTCF A. Alternatively the initial source of HBV infection may have been an individual who had left LTCF A prior to the initiation of the investigation and therefore was never tested.
Among the 4 new HIV diagnoses, pol
gene sequencing revealed that 2 sequences clustered and that 3 sequences had evidence of transmitted drug resistance. Although clustering does not establish an epidemiologic link between cases (intermediaries may exist), it does suggest that they are part of the same transmission network and interrupting transmission in these networks may be particularly important given the high proportion with transmitted drug resistance. Although integrating HIV medical care with psychiatric and addictive disorders care has been proposed 
, reducing HIV transmission among individuals with mental illness in LTCFs will also require integrating HIV prevention strategies that are tailored to these populations and their drug use and sexual networks.
Previous studies have shown that persons with severe mental illness engage frequently in high-risk behaviors including reported intravenous drug use 
and risky sexual behavior 
. The mentally ill residents of this LTCF were ambulatory and had unmonitored visits outside the facility. In addition, sexual activity among these residents was frequent according to staff interviews. Because of the potential for multiple sex partners and illicit intravenous drugs in the community, there may have been multiple routes of transmission of bloodborne pathogens among this cohort of mentally ill residents. Preventive interventions that target substance abuse and promote condom use during sex remain important tools to prevent new HBV, HCV, and HIV infections in mentally ill persons residing in LTCFs 
. While there are longstanding recommendations for routine hepatitis B vaccination for developmentally disabled persons in congregate living settings 
, no similar guidelines exist that recommend HBV vaccination among mentally ill residents in congregate housing. Our findings suggest a need for hepatitis B vaccination guidelines to be extended to include mentally ill residents in congregate settings.
Several limitations were encountered during this investigation. First, it was not possible to perform standardized interviews with this patient population because the severity of the mental illnesses of these residents precluded accurate answers with respect to risk factors for transmission of blood-borne pathogens. Second, it was not possible to track the whereabouts of community visits for the patients who were allowed to leave the facility. Third, medical records were limited with respect to documentation and previous results of HBV and HIV testing. These limitations led us to evaluate for molecular evidence of transmission and these molecular phylogenetic analyses provided strong additional evidence of HBV and HIV transmission among residents of this facility.
CCDPH made several recommendations to LTCF A to control and prevent further transmission among their residents. LTCF A was advised to screen mentally ill patients for HIV, HBV, and HCV at time of initiation of the outbreak investigation and then again at 3 and 6 months in order to identify additional infections. Ninety out of 160 susceptible residents who were eligible for HBV vaccination received the vaccine at least once. Resident education regarding safe sex practices was reinforced. There were no further acute HBV infections identified in the 6 months after the initiation of the investigation.
This outbreak demonstrates the need for continued efforts to prevent bloodborne pathogen transmission among severely mentally ill residents who reside in LTCFs. Screening for bloodborne pathogens 
including HIV, HBV, and HCV at the time of admission to a LTCF and at regular intervals thereafter is an important strategy to identify infected residents. HBV vaccination policies such as those recommended for mentally disabled individuals in congregate settings, should be considered for severely mentally ill in these types of LTCFs. Lastly, strategies aimed at risk reduction will be important to prevent further spread of these infections among LTCF populations.