Characterizing HIV and Tuberculosis Co-infection in Southern California

Timothy Rodwell M.D., Ph.D., University of California, San Diego
Basic-Applied Clinical

HIV is a potent risk factor for tuberculosis (TB). It increases the rate of latent TB reactivation, the rate of progression of the active disease and the risk of new infections by an order of magnitude. Active TB disease also affects HIV, accelerating progression of the HIV infection, increasing infectivity and reducing HIV treatment efficacy. About 13 million people are co-infected with HIV and TB worldwide, and mortality rates during treatment can be as high as 20% compared to the 5% treatment death rates that are more typical of TB cases without HIV co-infection.

In San Diego County, where the TB case rate is more than twice as high as the rest of the U.S., the annual incidence of HIV/TB co-infection has remained at about 10% of all TB cases despite a decline of both TB and HIV cases in the overall population. There is a concern that the preventive measures that have proved effective in the general community are not reaching the HIV/TB patient population. Preliminary analysis of the HIV/TB cohort reported to San Diego County over the last five years indicates that this population is comprised mostly of male immigrants (>70% Hispanic) and that over 15% of them die before TB treatment is completed--on average within 2.5 months of their TB diagnosis. Furthermore, there are grave concerns that if left unchecked, San Diego's largely immigrant HIV/TB population, which currently has a very low prevalence of Multi Drug Resistant (MDR) TB, will become infected with more strains of MDR-TB or the Extensively Drug Resistant (XDR) TB strains that have recently been discovered in California.

The synergy of HIV and TB co-infection and the unique risk environment of the patients that acquire these dual infections will require innovative and holistic approaches for management that are based on an intimate understanding of the epidemiology of both HIV and TB. The overall goal of this proposed project is to characterize the epidemiology of HIV and TB co-infection in San Diego and to develop an HIV/TB co-infection surveillance tool for long-term use. We have four specific aims: 1) To characterize risk factors for HIV infection in HIV/TB Cases in San Diego County using a two year prospective survey, 2) To determine the etiology of TB in HIV/TB Cases in San Diego County using genotype cluster analysis of TB isolates, 3) To characterize risk factors for TB infection among HIV/TB Cases in San Diego County using a 15 year retrospective analysis and lastly, 4) To identify risk factors associated with mortality during TB treatment among HIV/TB co-infected individuals, using a 15 year retrospective analysis and a two year prospective survey.

Increasingly specialized HIV and TB treatments and complex socio-economic barriers are widening the gap between the control and care of HIV and the control and care TB at a time when it is becoming clear that the best prevention and care is delivered when these dual infections are managed together. The proposed study will provide the first comprehensive characterization of both HIV and TB risk factors unique to San Diego County, as well as a clear understanding of the factors driving the high treatment mortality seen in this extraordinarily vulnerable patient group. Armed with insights from our project, we expect to be able to identify critical points of intervention for increasing the effectiveness of future preventive strategies and improving treatment outcomes in this population.