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TB and HIV, Tijuana, Mexico | CDC EID


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Volume 16, Number 5–May 2010
Research
Latent Tuberculosis among Persons at Risk for Infection with HIV, Tijuana, Mexico
Richard S. Garfein, Rafael Laniado-Laborin, Timothy C. Rodwell, Remedios Lozada, Robert Deiss, Jose Luis Burgos, Jazmine Cuevas-Mota, Paris Cerecer, Kathleen Moser, Maria Luisa Volker, and Steffanie A. Strathdee
Author affiliations: University of California San Diego School of Medicine, San Diego, California, USA (R.S. Garfein, T.C. Rodwell, R. Deiss, J.L. Burgos, J. Cuevas-Mota, S.A. Strathdee); Universidad Autonoma de Baja California, Tijuana, Mexico (R. Laniado-Laborin); Patronato Pro-Comité Municipal de Prevención del SIDA, Tijuana (R. Lozada); Instituto de Servicios de Salud Pública del Estado de Baja California, Tijuana (P. Cerecer, M.L. Volker); and San Diego County Department of Health and Human Services, San Diego (K. Moser)


Suggested citation for this article

Abstract
Because there is little routine tuberculosis (TB) screening in Mexico, the prevalence of latent TB infection (LTBI) is unknown. In the context of an increasing HIV epidemic in Tijuana, Mexico, understanding prevalence of LTBI to anticipate emergence of increased LTBI reactivation is critical. Therefore, we recruited injection drug users, noninjection drug users, female sex workers, and homeless persons for a study involving risk assessment, rapid HIV testing, and TB screening. Of 503 participants, the overall prevalences of TB infection, HIV infection, and TB/HIV co-infection were 57%, 4.2%, and 2.2%, respectively; no significant differences by risk group (p>0.05) were observed. Two participants had TB (prevalence 398/100,000). Incarceration in Mexico (odds ratio [OR] 2.28), age (OR 1.03 per year), and years lived in Tijuana (OR 1.02 per year) were independently associated with TB infection (p<0.05). Frequent LTBI in marginalized persons may lead to increases in TB as HIV spreads.
Tuberculosis (TB) is endemic to Mexico. The national TB incidence is estimated to be 16.2 cases/100,000, but regional rates, particularly along the United States–Mexico border are much higher (1). Baja California, which shares a border with California, has the highest incidence of pulmonary TB in Mexico (57 cases/100,000), which is >3× the national average (2). Furthermore, California and Baja California have the highest incidence rates of all the border states in their respective countries (1). Transmission of TB from high-prevalence countries to low-prevalence countries, such as the United States, poses a major public health concern. Tijuana, the largest city in Baja California, Mexico, lies ≈20 miles south of downtown San Diego, California, and these 2 cities are loosely separated by the busiest land border crossing in the world, with >90,000 passenger vehicles crossing in both directions daily (3). As a possible consequence of this close binational association, San Diego has a slightly higher incidence of TB than California (8.4 per 100,000 and 7.0 per 100,000, respectively) (4,5).

Otherwise healthy persons with dormant or latent tuberculosis infection (LTBI) have a 10% lifetime risk that dormant mycobacteria will become active and cause TB. Persons co-infected with HIV and LTBI have a risk for TB reactivation of 10% per year (6). Consequently, TB is a leading cause of death worldwide among persons co-infected with TB and HIV (7). Although HIV prevalence in Mexico is lower than that in the United States, Tijuana is currently experiencing an emerging HIV epidemic (8), with increasing prevalence observed among high-risk groups such as injection drug users (IDUs) and female sex workers (FSWs) (9–11). The potential for rapid HIV transmission among IDUs in Mexico is highlighted by findings from Tijuana and Ciudad Juarez (a border city south of El Paso, Texas), which showed that 95% of IDUs in these cities had antibodies against hepatitis C virus (a marker of unsafe injection practices), and most IDUs had self-reported risk factors for sexual or parenteral exposure to HIV (12). Thus, there is concern that increased HIV incidence would result in LTBI reactivation among IDUs who spread active TB to other populations, which would lead to a more generalized epidemic.

Homeless persons and noninjecting drug users (NIDUs) are also at increased risk for co-infection with TB/HIV. In low-prevalence countries, these risk groups have higher rates of LTBI than those in the general population (13–15). Although estimates of LTBI and their correlates among FSWs are not well documented, an increasing percentage of FSWs in Tijuana are infected with HIV and report multiple potential risk factors for TB, including injection drug use and sexual contact with IDUs (10). Thus, the need for accurate estimates of LTBI prevalence in high-risk marginalized populations is clear.

In the United States, LTBI screening and prophylactic treatment have played a major role in reducing co-infection with TB/HIV in most regions and communities. However, LTBI screening, which is usually conducted by using the tuberculin skin test (TST), is uncommon in countries such as Mexico, which still uses Mycobacterium bovis BCG vaccination universally, because the TST has reduced specificity in vaccinated persons (16). Whole-blood interferon-γ release assays (IGRAs), which measure cellular immune response to purified proteins found in M. tuberculosis, but not in BCG vaccine strains, provide a means for more accurately estimating TB infection prevalence in countries such as Mexico (17). A study that measured TB infection prevalence in Mexico by using an IGRA found that 67% of IDUs in Tijuana were positive (18). However, that study did not differentiate between LTBI and active TB and included only IDUs. The purposes of the current study, known as PreveTB, were to measure the prevalence of TB and HIV among marginalized populations of Tijuana who are at a high risk for becoming co-infected with HIV and TB, estimate the prevalence of active TB in this group, and identify correlates of LTBI.

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TB and HIV, Tijuana, Mexico | CDC EID

Suggested Citation for this Article
Garfein RS, Laniado-Laborin R, Rodwell TC, Lozada R, Deiss R, Burgos JL, et al. Latent tuberculosis among persons at risk for infection with HIV, Tijuana, Mexico. Emerg Infect Dis [serial on the Internet]. 2010 May [date cited]. http://www.cdc.gov/EID/content/16/5/757.htm

DOI: 10.3201/eid1605.091446

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