Measles aerosol vaccination.

Measles ranks fifth among the five major childhood conditions which are responsible for 21% of all deaths in low and middle-income countries. Measles immunization is considered the most cost-effective public health intervention in the world. In recent years, there has been a critical need to identify alternative routes of measles immunization, which are rapid, reliable, cost-effective, needle-free, and suitable for use in mass campaigns. Aerosol administration of measles vaccines in mass campaigns was first proposed by Dr. Albert Sabin. We review the different clinical trials that have been conducted using the classic Mexican device as well as issues regarding vaccine strain, presentation, and manufacturer. Results of clinical trials indicate that the method is safe and immunogenic in infants and school age children. The viral inoculum will probably need to be increased when administered to infants. From the logistical point of view, the use of the aerosol method has not been evaluated in routine immunization although feasibility of its routine implementation was proved in mass campaigns in Mexico. Cost savings will probably be demonstrated. As to licensure, its compliance with the appropriate international regulatory requirements for medical aerosol delivery devices is in process.

[Drug resistance of Mycobacterium tuberculosis in Orizaba, Veracruz. Implications for the tuberculosis prevention and control program]. / Resistencia de Mycobacterium tuberculosis a los antimicrobianos en Orizaba, Veracruz. Implicaciones para el Programa de Prevención y Control de la Tuberculosis.

BACKGROUND: Tuberculosis, declared a global emergency by the World Health Organization, continues to be an important public health problem in Mexico, included in the first twenty causes of death. OBJECTIVE: To know the impact of drug resistance of Mycobacterium tuberculosis on treatment outcome, need of re-treatment and mortality in a cohort of patients with pulmonary tuberculosis receiving directly observed therapy, short course (DOTS). METHODS: We conducted a population-based study in a suburban region in Southern Mexico. People who had been coughing for more than two weeks underwent sputum acid-fast bacilli smear. Patients with a positive smear were recruited and underwent clinical exam, chest X-ray, HIV testing, and sputum cultures. Identification, drug susceptibility testing and restriction fragment length polymorphism analysis (RFLP) were performed in all isolates. Patients were followed every 12 months for new episodes of tuberculosis and vital status. Patients were referred for clinical care to the local program of tuberculosis. Deaths were corroborated with death certificates. Informed consent was obtained from participants. RESULTS: Between March 1995 and February 1999, tuberculosis was diagnosed in 371 patients who were followed for an average of 32 months. M. tuberculosis was cultured from 316 patients; resistance to any drug occurred in 25.0% of isolates (primary 18.8%, acquired 49.2%); only to isoniazid in 6.8% (primary 7.3%, acquired 4.8%); to isoniazid and rifampin in 6.2% (primary 1.6%, acquired 23.8%). Patients with drug resistance had a higher probability of treatment failure (OR = 16.9, CI 95% 4.5-63.0) and patients with MDR strains had a higher probability of need of re-treatment (RR = 24.4, CI 95% 8.8-67.6), and of death (RR = 4.0, CI 95% 1.5-10.7). Additional variables were found to be associated with subsequent episodes of disease and mortality: Cocaine use, chronic disease, type of radiological lesions, HIV co-infection, non-compliance and treatment delay, as well as RFLP clustering. CONCLUSIONS: In this study, we observed that drug resistance showed a severe impact on the outcome and survival; drug-resistance was the most significant factor for these negative outcomes; DOTS may not be sufficient in areas where drug resistance is considerable, and patient follow-up for longer periods of time, as compared to evaluation at the end of treatment, provides additional information which is useful for prevention and control programs.

Nosocomial infections in a community hospital in Mexico.

Results from prospective surveillance of nosocomial infections (NIs) in a small community hospital were evaluated, and a case-control study was conducted. The rate of 1.4 NIs per 100 discharges determined by prospective surveillance was found to be underestimated. Prematurity, pediatric service, surgery, length of stay, and age were independently associated with NI.

Factors associated with tuberculin reactivity in two general hospitals in Mexico.

OBJECTIVE: To identify risk factors associated with tuberculin reactivity in healthcare workers (HCWs). DESIGN: Cross-sectional survey of tuberculin reactivity (2 TU of purified protein derivative (PPD) RT23, using the Mantoux two-step test). SETTING: Two general hospitals located in a region with a high prevalence of tuberculosis and high bacille Calmette-Guerin (BCG) coverage. PARTICIPANTS: Volunteer sample of HCWs. RESULTS: 605 HCWs were recruited: 71.2% female; mean age, 36.4 (standard deviation [SD], 8.2) years; 48.9% nurses, 10.4% physicians, 26.8% administrative personnel; mean time of employment, 10.9 (SD, 6.7) years. PPD reactivity (> or =10 mm) was found in 390 (64.5%). Multivariate analysis revealed an association of tuberculin reactivity with occupational exposure in the hospital: participation in autopsies (odds ratio [OR], 9.3; 95% confidence interval [CI95], 2.1-40.5; P=.003.), more than 1 year of employment (OR, 2.4; CI95, 1.1-5.0; P=.02), work in the emergency or radiology departments (OR, 2.0; CI95, 1.03-3.81; P=.04), being physicians or nurses (OR, 1.5; CI95, 1.04-2.11; P=.03), age (OR, 1.04; CI95, 1.02-1.07 per year of age; P<.001), and BCG scar (OR, 2.1; CI95, 1.2-3.4; P=.005). CONCLUSIONS: Although the studied population has a high baseline prevalence of tuberculosis infection and high coverage of BCG vaccination, nosocomial risk factors associated with PPD reactivity were identified as professional risks; strict early preventive measures must be implemented accordingly.

[The ABCs on anthrax for health personnel]. / El A, B, C, sobre ántrax, para personal de salud.

The purpose of this series of articles is to present to health personnel an updated summary on bioterrorism associated agents. In this first article an updated summary on anthrax is presented. Emphasis has been placed on the characteristics of cases which occurred during October in the United States of America and on the experience of governmental agencies of that country to face the emergency. Measures implemented in Mexico are described as well. The authors are convinced that the best arm against terror is timely and updated information.

Underestimation of Mycobacterium tuberculosis infection in HIV-infected subjects using reactivity to tuberculin and anergy panel.

BACKGROUND: This study aimed to evaluate purified protein derivative (PPD) reactivity and its interrelationship with anergy panel and CD4+ lymphocytes in HIV-infected subjects as compared to PPD reactivity in HIV-uninfected individuals in a tuberculosis endemic and high Bacillus Calmette-Guérin (BCG) coverage environment. METHODS: Clients of four Mexico City HIV detection centres were screened for HIV-1 antibodies (ELISA or haemagglutination, Western Blot); reactivity to PPD (Mantoux PPD, 5TU RT-23), Candida (1:1000, 0.1 ml), and tetanus toxoid (10Lf, 0.1 ml); and CD4+ T cells. Active tuberculosis was excluded. Informed consent was obtained. RESULTS: From 5130 clients 1168 subjects were enrolled; of these 801 (68.6%) were HIV positive. Reactivity to PPD among HIV-positive subjects was found in 174 (22%), 261 (32.6%), and 296 (37%), at PPD cutoff levels of > or =10 mm, > or =5 mm, and > or =2 mm as compared to 224 (61%) of 367 HIV-negative individuals' reactors to PPD (> or =10 mm) (P < 0.001). After exclusion of anergic individuals using two cutoff levels for cutaneous allergens (< or =2 mm and < or =5 mm), PPD reactivity between HIV-infected and uninfected individuals continued to be significantly different. Only HIV-infected individuals with CD4+ T cells > or =500 cells/mm3 had similar reactivity to PPD as HIV-uninfected individuals. Variables associated with PPD reactivity were CD4+ T cell counts, BCG scar, HIV infection and age. CONCLUSIONS: PPD reactivity was useful to diagnose tuberculosis infection only among HIV-infected individuals with CD4+ counts > or =500 cells/mm3. Among individuals with lower counts, lowering cutoff levels or using anergy panel did not permit comparable reactivity as that observed among HIV-uninfected individuals.

Clinical consequences and transmissibility of drug-resistant tuberculosis in southern Mexico.

BACKGROUND: Consequences of drug-resistant tuberculosis (TB) in developing countries using directly observed treatment, short-course (DOTS), are not well defined. OBJECTIVE: To determine the impact of drug resistance on clinical outcome and transmission of TB under programmatic conditions. PATIENTS AND METHODS: A prospective cohort and molecular epidemiologic study was conducted in southern Mexico. Between March 1995 and February 1998 all patients with persistent cough whose sputa had acid-fast bacilli (AFB) underwent clinical and mycobacteriologic evaluation (species identification, drug susceptibility testing, and IS6110-based genotyping). Treatment was provided in accordance with Mexico's National Tuberculosis Program. Clinical and microbiologic outcomes and molecular epidemiologically defined transmission were measured. RESULTS: Mycobacterium tuberculosis was isolated from 238 of the 284 AFB smear-positive persons. The overall rate of resistance was 28.4% (new, 20.7%; retreated, 54.7%), and 10.8% (new, 3.3%; retreated, 35.8%) had multi-drug-resistant TB (ie, resistance to isoniazid and rifampin). After treatment, 75% (new, 81.0%; retreated, 52.8%) were cured, 8% (new, 7.8%; retreated, 7.5%) abandoned therapy, 9% (new, 3.9%; retreated, 28.3%) had treatment failure, and 4% (new, 3.3%; retreated, 7.5%) died. Another 2% of patients relapsed, and 9% died during a median of 24.4 months of follow-up. Drug-resistance was a strong independent risk factor for treatment failure. Being infected with multi-drug-resistant TB was the only factor associated with a decreased likelihood of being in a restriction fragment length polymorphism cluster. CONCLUSIONS: Despite the use of DOTS, patients with drug-resistant TB had a dramatically increased probability of treatment failure and death. Although multi-drug-resistant TB may have a decreased propensity to spread and cause disease, it has a profoundly negative impact on TB control.

The role of core groups in transmitting Mycobacterium tuberculosis in a high prevalence community in Southern Mexico.

SETTING: A community in Southern Mexico with a high prevalence of tuberculosis. OBJECTIVE: To characterize the transmission dynamics in a region with a DOTS-based tuberculosis control program. DESIGN: Community-based screening of chronic coughers between 1 March 1995 and 31 August 1996. Individuals with acid-fast bacilli (AFB) in their sputum were enrolled, interviewed, and had mycobacterial cultures and fingerprinting performed. In-depth interviews were conducted on all persons with DNA fingerprinting. RESULTS: AFB smears were performed on 1424 individuals, 124 of whom were microbiologically confirmed. Of the 95 cases for whom bacterial DNA fingerprints were available, 38 were in clusters. The largest cluster involved seven individuals who were members of a social network centered on a series of unlicensed bars. CONCLUSION: This population-based molecular epidemiologic study showed that a focus of transmission within a social network accounted for one fourth of transmission which rapidly progressed to disease. These observations raise questions about the potential benefit of targeted tuberculosis control interventions in health jurisdictions approaching WHO-defined DOTS benchmarks.

Mycobacterium tuberculosis drug resistance in a suburban community in southern Mexico.

OBJECTIVE: To determine the impact of drug resistance (DR) on the clinical outcome and transmission of tuberculosis under programmatic conditions. METHODS: Prospective cohort and molecular epidemiologic study in the Orizaba Health Jurisdiction of Mexico. Between March 1995 and July 1999, chronic coughers with positive acid-fast bacilli (AFB) detected in sputum smear underwent clinical and mycobacteriologic evaluation (species identification, drug susceptibility testing and IS6110-based genotyping). Treatment was provided in accordance with official norms. RESULTS: Mycobacterium tuberculosis was isolated from 326/387 AFB-positive cases. The rate of DR was 24.2% and that of multidrug resistance (MDR, defined as resistance to both isoniazid and rifampin at least) was 7.7%; 78% were cured, 8% abandoned treatment, 6% failed treatment, and 5% died. An additional 13.5% received retreatment and 8.9% died during a median 28.6 months of follow up. Factors associated with DR by multivariate analysis were chronicity of tuberculosis (OR 4.8, 95%CI 2.7-8.4, P < 0.001), age >40 years (OR 1.9, 95%CI 1.1-3.2, P = 0.02) and indigenous origin (OR 0.3, 95%CI 0.13-0.75, P = 0.01). Cox-adjusted relative risks showed that MDR (RR 2.5, 95%CI 1.02-6.16, P = 0.04), HIV infection (RR 31.3, 95%CI 11.6-84.8, P < 0.001), and chronicity of tuberculosis (RR 2.1, 95%CI 1.0-4.4, P = 0.06) were associated with mortality, controlling for age. Predictors of retreatment were DR (not including MDR) (RR 2.2 95%CI 0.89-5.31, P < 0.087), MDR (RR 12.6, 95%CI 5.46-28.88, P < 0.001), and living in a household with an earthen floor (RR 2.8, 95%CI 1.27-6.13, P = 0.011). Being infected with MDR-TB was the only factor associated with a decreased likelihood of being in an RFLP cluster (OR 0.31, 95%CI 0.12-0.81, P = 0.02). CONCLUSIONS: Although MDR-TB may have a decreased propensity to spread and cause disease, it has a profoundly negative impact on tuberculosis control.

Prevalence and risk of cysticercosis and taeniasis in an urban population of soldiers and their relatives.

To determine markers of Taenia solium transmission and risk factors in an urban community, we studied 1,000 soldiers from a military camp in Mexico City and their relatives. Serum samples were used to detect antigens and antibodies and fecal specimens were examined for Taenia coproantigens and helminth eggs. Prevalences of 12.2% and 5.8% for cysticercosis were found among soldiers and their relatives, respectively. Taeniasis was found in 0.5% and none of the groups, respectively. Relatives of soldiers positive for cysticercosis and taeniasis markers ate more pork from street stores than restaurants or markets compared with relatives of soldiers without these indicators of infection. Also, 12.0% of the relatives of positive soldiers had a history of expelling tapeworm proglottids in the feces in contrast to 3.7% of the family members of the control group. Prevalence values and risk factors in this urban population are similar to those of previous studies performed in rural populations.

Tuberculosis epidemiology and control in Veracruz, Mexico.

BACKGROUND: Tuberculosis (TB) rates remain high in regions of Southern Mexico despite the existence of a National Tuberculosis Program. Understanding TB epidemiology in such settings would assist in the design of improved TB control and highlight the challenges confronting TB control in developing countries. METHODS: We conducted a retrospective review of treatment control cards from 1991 to 1994 in five municipalities in a semiurban region of Southern Mexico. RESULTS: The relatively high rate of TB observed, 42.6 per 100,000 inhabitants, did not change significantly during the study period. Cure rates among new cases were 79% and significantly lower among retreatment cases (62%). Directly observed therapy (DOT) was administered to 84% of patients. Approximately one-half of the retreatment cases who were not cured were compliant with therapy, suggesting that drug resistance contributed to these poor results. Of particular concern was a core group of 16 patients who had received at least three treatments. CONCLUSIONS: This region of Mexico has persistently high TB rates despite a DOT-based TB control programme which achieves an overall cure rate of 77%. There exist many retreatment cases for whom cure rates are significantly lower. These cases may serve as a core group for the dissemination of drug resistant TB. The control programme is being reinforced by a nominal register of patients, decreasing administrative barriers for drug supply to individual patients and the availability of mycobacteria cultures. In addition to these measures, in regions which are approaching the levels of efficacy recommended by the WHO it may be appropriate to consider focusing efforts on the identification and treatment of chronic cases.

[Efficacy and efficiency of antitubercular treatment in health jurisdictions of Morelos]. / Eficacia y eficiencia del tratamiento antituberculoso en jurisdicciones sanitarias de Morelos.

OBJECTIVE: To evaluate the efficacy and efficiency of tuberculosis treatment administered by the Secretaría de Salud (SSA) in the sanitary jurisdictions of Cuernavaca and Cuautla, Morelos, for the 1992-1996 period by retrospectively reviewing tuberculosis treatment control cards. MATERIAL AND METHODS: Official Norm for Tuberculosis Prevention and Control in Primary Care Units outcome definitions were used. Data was collected on standardized forms and analyzed with SAS and Epi Info programs; 149 primary care units and 4 hospitals in the study area were visited. RESULTS: There were found 288 patients cards, of which 260 were new cases. These patients received 311 treatments of which 85% were directly observed. Reviewed cards represented 60% of SSA notified cases for this period. There were analyzed 246 treatments of which 32% were bacteriological cures, 26% probable cures, 18% dropouts, 1% failures and 3% deaths. In 20% of treatments the outcome was unknown. Cure rate was better in new cases (61%) than in retreatments (38%), p < 0.01. Efficacy of treatment was 71% and efficiency 58%. Patients receiving retreatment abandoned it more frequently (32%) than new cases (16%), p < 0.01. A statistically significant association was found between abandoned treatment and being retreated (OR = 3.3, CI 95% 1.3-8.5, p = 0.01) or belonging to a lower socioeconomic level (OR = 2.3, CI 95% 1.0-4.9, p = 0.04). In the 34 retreatment programs, 22 were initiated after abandonment, failure or relapse. CONCLUSIONS: Proportion of cure rate (58%) compares unfavorably with WHO recommendations (85%). Implications of a high dropout rate and probability of circulation of resistant strains of M tuberculosis are discussed. Creative strategies to reinforce patient compliance which take into account the patient and not only the health services, extension of cultures to known M. tuberculosis drug resistance and evaluation of modifications to drug regimens are proposed. Review of treatment control cards is a useful tool for program evaluation.

[Measles vaccination by the aerosol method in Mexico]. / La vacunación antisarampionosa en México por el método de aerosol.

The present work describes the anti-measles vaccination program by the inhaled aerosol method undertaken in Mexico between 1988 and 1990. Detailed descriptions are given of the equipment, staff, training programs, promotion and campaigns. The vaccine is specified: Edmonston-Zagreb strain cultured in diploid cells at the Instituto Nacional de Virología of the Secretaría de Salud in Mexico with titres varying from 1045 plaque forming units (PFU/ml) to 1048 PFU/ml administered in a 30 sec inhalation with aerosol. During this exposure period, 2800 to 4000 PFU per child are estimated to enter the child, of which approximately 25% is the retained doses, i.e. 700 to 1000 PFU/child. A total of 3760684 children of school and pre-school age have been vaccinated in 13 of the 32 federal entities of the country. No undesirable effects of any importance were observed, and the limited serological and field studies support the effectiveness and security of this method. On the other hand, the method is much cheaper, faster and better accepted by the population than the subcutaneous injection.

[The epidemiology of AIDS/HIV in Mexico: from 1983 to March 1995]. / Epidemiología del SIDA/VIH en México; de 1983 a marzo de 1995.

The purpose of this study is to analyze the HIV/AIDS magnitude, distribution, frequency, patterns, trends, risk factors, risk groups, estimation and evaluation of interventions in Mexico during the last twelve years. Results of a summary of statistics and results from several sources are presented including the National Registry of AIDS cases, HIV sentinel surveillance in 18 cities of the country, analysis of death certificates, cross-sectional, longitudinal, observational, and intervention studies. As of March 1995, 34,230 AIDS cases, 120,000 HIV infections and 21,000 AIDS deaths are estimated. A damaged exponential growth with duplication of AIDS cases every 18 months can be seen. Epidemiological patterns of transmission are found primarily among men with homosexual and bisexual practices. The male:female ratio is 6 to 1. In 1992 AIDS was the 19th cause of death among the general population. At least two patterns of transmission have been identified: one is the western-urban pattern which contributes with more than 90% of cases and the other, more recent, has been described as Caribbean-rural. Blood transmission of AIDS shows a downward trend, and heterosexual and perinatal transmission is slightly increasing. Seroprevalence among adults is 0.06%: however, among groups with risk practices, rates up to 50% have been found. Risk factors are similar to those described in the literature in other countries, and have been used for designing interventions. Evaluation of interventions has been accomplished by demonstrating positive results in the prevention of blood transmission and sexual transmission among female commercial sex workers; prevention efforts directed to men with homosexual practices have not been successful. Between 77,000 and 88,000 cumulated AIDS cases are estimated in Mexico for the year 2000.

[The HIV/AIDS epidemic and women in Mexico]. / La epidemia de VIH/SIDA y la mujer en México.

This study presents an analysis of AIDS cases and seroprevalence of HIV infection among Mexican women, from the onset of the epidemic through June 1994, as well as the analysis of the social and cultural factors that put women in a powerless situation regarding the adoption of preventive measures. Since 1985, when the first AIDS cases among women were reported in Mexico and until June 1, 1994, a total of 2,767 cases have been reported, representing 14.8% of the total number of cases. The first cases of AIDS among women were associated to infected blood transfusions; however, in 1986, heterosexually transmitted cases began to appear. Currently, only 35% of newly reported AIDS cases are associated to blood transfusions while 64% of them are related to heterosexual transmission. In fact, two epidemics are evident: one transmitted through blood, showing a downward trend (duplication time 45 months), and a second one, heterosexually transmitted, increasing twice as fast (duplication time 27 months). The latter is expected to dominate AIDS epidemiology among women in the future. In general, women are more vulnerable to HIV/AIDS biologically, but also socially and culturally. Women's economic, social and cultural subordination to their sexual partners results in a situation that makes it difficult for them to assess their infection risk and even more, to negotiate taking preventive measures. This situation is even more disadvantageous to rural women and, together with the recent trend of the AIDS epidemic to ruralization and with internal and international migration (temporary work force migration to the USA), can result in deep demographic and social effects. We conclude that it is necessary to work on the design and assessment of preventive measures under women's control, that empower them to protect themselves even without their partner's awareness. Also, it is necessary to promote sexual education among young heterosexual couples on how to talk about sexual issues and negotiate the use of preventive measure according to their actual sexual practices.

[Tuberculosis and AIDS in Mexico]. / Tuberculosis y SIDA en México.

Tuberculosis (TB) still is an important health problem in Mexico. According to reported figures, an excess in the number of cases has occurred during recent years, mainly among young adults of both sexes. The present estimated rate of TB is 51.7 cases/100,000 inhabitants. This is the most frequent endemic infection among AIDS patients, ranking third among infectious diseases after candidiasis and P. carinii pneumoniae. A total of 8.3% of the 19,352 AIDS cases notified to July 1994, presented TB as the initial manifestation. According to sentinel surveillance carried out since 1990 in 17 states, HIV seroprevalence among TB patients has been 3.1% (0-6.5%) in males and 1.0% (0-2.3%) in females. Results of epidemiologic research in the field of TB prevention and characteristics of drug sensitivity of strains of M. tuberculosis isolated from HIV/AIDS patients are also described. Finally, perspectives of TB prevention and control are discussed.

[Sexually transmitted diseases and the HIV/AIDS epidemic]. / Las enfermedades de transmisión sexual y la epidemia de VIH/SIDA.

Studies on sexually transmitted diseases (STD) during the previous years in Mexico are discussed. The information sources were: a) Surveys among commercial sex workers. Since 1990, 1,386 women have been studied in four federal states through structured questionnaires and laboratory tests. Prevalence of different STD's has been significant (syphilis (VDRL, FTA-abs) 23.7%; chlamydiosis (Ag IF) 12.9%; gonorrhea (Ag, ELISA) 11.5%; anti-HBs 11.0%; herpes 1,2 (IgM) 9.3%, HBsAg 5.7%. Frequency of HIV (ELISA, Western blot) has been low; 0.5%. In 1994, 662 women were studied in Mexico City, with different laboratory techniques for chlamydiosis and gonorrhea (culture), hepatitis B (anticore antibodies) and herpes (total antibodies) with the following results: syphilis 1.5-12%; chlamydiosis 10.8-11.7%; gonorrhea 0-5.9%; hepatitis B 0-7.1%; herpes 44.7-78%; and HIV 0-1.4%. b) Surveys among men with homosexual and bisexual practices. 325 subjects have been studied in three federal states using methods similar to those of the 1990 survey. Contrasting with results among women, HIV prevalence was found to be high; (18.8%), and considerable for other STD's: anti-HBsAg 28.6%, syphilis 34.9%, recent herpes 10.9%, HBsAg 5.0%, chlamydiosis (Ag, IF) 4.3%, herpes simplex 1,2 (Ag, IF) 4.7%, gonorrhea (Ag, ELISA) 2.8%. c) Patient clinical studies. The clinical interrelationship between different STD and HIV infection has been studied; clinical differences are described between patients with condylomata or syphilis depending on HIV serostatus. Implications of the interrelationship between different STD's and HIV infection for the prevention and control of these diseases are discussed.