The Indigenous South American Tsimane Exhibit Relatively Modest Decrease in Brain Volume With Age Despite High Systemic Inflammation.

Brain atrophy is correlated with risk of cognitive impairment, functional decline, and dementia. Despite a high infectious disease burden, Tsimane forager-horticulturists of Bolivia have the lowest prevalence of coronary atherosclerosis of any studied population and present few cardiovascular disease (CVD) risk factors despite a high burden of infections and therefore inflammation. This study (a) examines the statistical association between brain volume (BV) and age for Tsimane and (b) compares this association to that of 3 industrialized populations in the United States and Europe. This cohort-based panel study enrolled 746 participants aged 40-94 (396 males), from whom computed tomography (CT) head scans were acquired. BV and intracranial volume (ICV) were calculated from automatic head CT segmentations. The linear regression coefficient estimate ß^T of the Tsimane (T), describing the relationship between age (predictor) and BV (response, as a percentage of ICV), was calculated for the pooled sample (including both sexes) and for each sex. ß^T was compared to the corresponding regression coefficient estimate ß^R of samples from the industrialized reference (R) countries. For all comparisons, the null hypothesis ß T = ß R was rejected both for the combined samples of males and females, as well as separately for each sex. Our results indicate that the Tsimane exhibit a significantly slower decrease in BV with age than populations in the United States and Europe. Such reduced rates of BV decrease, together with a subsistence lifestyle and low CVD risk, may protect brain health despite considerable chronic inflammation related to infectious burden.

Neuroimaging and Psychometric Assessment of Mild Cognitive Impairment After Traumatic Brain Injury.

Traumatic brain injury (TBI) can be serious partly due to the challenges of assessing and treating its neurocognitive and affective sequelae. The effects of a single TBI may persist for years and can limit patients' activities due to somatic complaints (headaches, vertigo, sleep disturbances, nausea, light or sound sensitivity), affective sequelae (post-traumatic depressive symptoms, anxiety, irritability, emotional instability) and mild cognitive impairment (MCI, including social cognition disturbances, attention deficits, information processing speed decreases, memory degradation and executive dysfunction). Despite a growing amount of research, study comparison and knowledge synthesis in this field are problematic due to TBI heterogeneity and factors like injury mechanism, age at or time since injury. The relative lack of standardization in neuropsychological assessment strategies for quantifying sequelae adds to these challenges, and the proper administration of neuropsychological testing relative to the relationship between TBI, MCI and neuroimaging has not been reviewed satisfactorily. Social cognition impairments after TBI (e.g., disturbed emotion recognition, theory of mind impairment, altered self-awareness) and their neuroimaging correlates have not been explored thoroughly. This review consolidates recent findings on the cognitive and affective consequences of TBI in relation to neuropsychological testing strategies, to neurobiological and neuroimaging correlates, and to patient age at and assessment time after injury. All cognitive domains recognized by the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) are reviewed, including social cognition, complex attention, learning and memory, executive function, language and perceptual-motor function. Affect and effort are additionally discussed owing to their relationships to cognition and to their potentially confounding effects. Our findings highlight non-negligible cognitive and affective impairments following TBI, their gravity often increasing with injury severity. Future research should study (A) language, executive and perceptual-motor function (whose evolution post-TBI remains under-explored), (B) the effects of age at and time since injury, and (C) cognitive impairment severity as a function of injury severity. Such efforts should aim to develop and standardize batteries for cognitive subdomains-rather than only domains-with high ecological validity. Additionally, they should utilize multivariate techniques like factor analysis and related methods to clarify which cognitive subdomains or components are indeed measured by standardized tests.

Multimodal Imaging of Cerebral Microhemorrhages and White Matter Degradation in Geriatric Patients with Mild Traumatic Brain Injury.

Traditionally, neurobiologists have utilized microscale techniques of scientific investigation to uncover the fundamental organization and function of brain cells and neuronal ensembles. In recent decades, however, macroscale brain imaging methods like magnetic resonance imaging (MRI) and computed tomography (CT) have facilitated a wider scope of understanding neural structure and function across the lifespan. Thanks to such methods, a broader picture of the relationship between microscale processes-studied by neurobiologists-and macroscale observations-made by clinicians-has emerged. More recently, the vascular component of neurodegeneration has come under renewed scrutiny partly due to increased appreciation of the relationship between neurovascular injury, cardiovascular disease, and senescence. Cerebral microbleeds (CMBs) are among the smallest lesions of the cerebrum which can be visualized using MRI to indicate blood-brain barrier (BBB) impairment; as such, this class of hemorrhages are important for the evaluation and macroscale detection of geriatric patients' microscale pathologies associated with neurovascular disease and/or neurodegeneration. This chapter details a streamlined protocol for MRI/CT multimodal imaging data acquisition, archiving and digital processing, including methods tailored for the analysis of susceptibility-weighted imaging (SWI) and diffusion-weighted imaging (DWI) scans to reveal CMB-related alterations of the human connectome. Efficient and effective MRI/CT methods like ours, when tailored for CMB and connectome analysis, are essential for future progress in this important field of scientific inquiry.

Post-Traumatic Cerebral Microhemorrhages and their Effects Upon White Matter Connectivity in the Aging Human Brain.

Cerebral microbleeds (CMBs), a common manifestation of mild traumatic brain injury (mTBI), have been sporadically implicated in the neurocognitive deficits of mTBI victims but their clinical significance has not been established adequately. Here we investigate the longitudinal effects of post-mTBI CMBs upon the fractional anisotropy (FA) of white matter (WM) in 21 older mTBI patients across the first ~6 months post-injury. CMBs were segmented automatically from susceptibility-weighted imaging (SWI) by leveraging the intensity gradient properties of SWI to identify CMB-related hypointensities using gradient-based edge detection. A detailed diffusion magnetic resonance imaging (dMRI) atlas of WM was used to segment and cluster tractography streamlines whose prototypes were then identified. The correlation coefficient was calculated between (A) FA values at vertices along streamline prototypes and (B) topological (along-streamline) distances between these vertices and the nearest CMB. Across subjects, the CMB identification approach achieved a sensitivity of 97.1% ± 4.7% and a precision of 72.4% ± 11.0% across subjects. The correlation coefficient was found to be negative and, additionally, statistically significant for 12.3% ± 3.5% of WM clusters (p <; 0.05, corrected), whose FA was found to decrease, on average, by 11.8% ± 5.3% across the first 6 months post-injury. These results suggest that CMBs can be associated with deleterious effects upon peri-lesional WM and highlight the vulnerability of older mTBI patients to neurovascular injury.

Polymorphisms of the dopamine D2 receptor, serotonin transporter, and GABA(A) receptor beta(3) subunit genes and alcoholism in Mexican-Americans.

The etiology of alcohol dependence is a complex interaction of psychosocial and biologic factors. To study the impact of genetic factors that play an important role in an individual's vulnerability to alcohol abuse and dependence, we examined the genetic variations of the major neurotransmitter genes, including the dopamine D2 receptor (DRD2) TaqI A, B, and -141C insertion/deletion (Ins/Del) polymorphisms, the serotonin transporter-linked polymorphic region (5-HTTLPR), and the gamma-aminobutyric acid A (GABA(A)) receptor beta(3) subunit gene (GABRbeta3), for 130 Mexican-American alcoholic men and 251 nonalcoholic control subjects (105 men and 146 women). The genotype frequency for the DRD2 -141C Ins/Del allele was significantly different between alcoholic and control subjects (P=.007). The frequency of the 5-HTTLPR short (S) allele was significantly higher in alcoholic individuals (61.5%) than in nonalcoholic control subjects (52.8%; P=.021). When smokers were excluded from both control and alcoholic groups, the association between the DRD2 -141C Ins allele, as well as between the 5-HTTLPR S allele, and alcoholism became significant at both genotypic and allelic levels. No positive association was found between alcoholism and the DRD2 TaqI A or B, or the GABRbeta3, genotype. Our findings indicate that the DRD2 -141C Ins allele and the 5-HTTLPR S allele are genetic risk factors for alcoholism in Mexican-Americans, and that smoking modulates the association between genetic risk factors and alcoholism.

ADH1B*1, ADH1C*2, DRD2 (-141C Ins), and 5-HTTLPR are associated with alcoholism in Mexican American men living in Los Angeles.

BACKGROUND: The aim of the present study was to use a candidate gene approach to identify the genetic risk factors for alcoholism in Mexican Americans residing in the Los Angeles area. The genes selected include alcohol metabolizing genes and neurotransmitter genes, which have been shown in the literature to be associated with alcoholism in other ethnic groups. METHODS: Thirteen allelic variants from seven genes were evaluated for their role in alcoholism using alcoholic (n = 200) and nonalcoholic (n = 251) Mexican Americans. Those polymorphic sites include alcohol dehydrogenase (ADH1B, ADH1C), aldehyde dehydrogenase (ALDH2), cytochrome P-450 2E1 (CYP2E1) TaqI, DraI, RsaI, dopamine D2 receptor (DRD2) TaqI A, B, intron 6, exon 7, -141C Ins/Del, serotonin transporter (5-HTTLPR), and GABAA receptor beta3 subunit (GABRbeta3). RESULTS: The results demonstrate that Mexican Americans have extremely low allele frequency for both ALDH2*2 and ADH1B*2 and a relatively high frequency of ADH1C*2 and CYP2E1 c2 alleles. ADH1B*1, ADH1C*2, DRD2 (-141C Ins), and 5-HTTLPR were associated with alcoholism in Mexican Americans (p < 0.05). DRD2 Ins was associated with alcoholism in those alcoholics who carried the ADH1B*2 or ADH1C*1 protective alleles (p = 0.032 in genotype level and p = 0.015 in allele level). DRD2 TaqI A and B alleles were associated with early age of onset for drinking (p = 0.016 for TaqI A1 and p = 0.049 for TaqI B1 allele). CONCLUSIONS: Together, the data reveal unique genetic patterns in Mexican Americans that may be in part responsible for the heightened risk for alcoholism and alcohol-associated health problems in this population.

The ADH3*2 and CYP2E1 c2 alleles increase the risk of alcoholism in Mexican American men.

To identify the association between the polymorphisms of genes encoding alcohol metabolizing enzymes and alcoholism, the alcohol dehydrogenase 2 (ADH2), alcohol dehydrogenase 3 (ADH3), aldehyde dehydrogenase 2 (ALDH2), and cytochrome P450 2E1 (CYP2E1) genes were studied in 101 male Mexican American alcoholics. One hundred and four Mexican American nonalcoholic males served as controls. The allele frequency of ADH2*2 (4.3%) and ALDH2*2 (0%), which are considered as protective alleles against alcohol drinking, is very low in Mexican Americans and no association is found between these alleles and alcohol dependence. A strong association was found between ADH3 genotype and alcoholism; the percentage of subjects who carry the ADH3*2 allele was significantly higher in alcoholics (64.4%) than controls (50%). Association was also found between the CYP2E1 RsaI c2 allele and alcohol dependence; the percentage of subjects who carry the RsaI c2 allele was significantly higher in alcoholics (34.7%) than in nonalcoholics (22.1%). The subjects whose alcohol drinking onset age is younger than 25 have much higher CYP2E1 c2 allele frequency than those whose alcohol drinking onset age is older than 25 (22.1% vs 15.7%). Among 101 alcoholics, only 18 subjects carry neither ADH3*2 nor CYP2E1 c2 alleles. For those subjects who have an ADH*1/*1 background, a strong association is found between CYP2E1 RsaI/DraI genotype and alcoholism; the CYP2E1 RsaI c2 and DraI C allele frequencies are much higher in alcoholics than in nonalcoholics (26.4% vs 9.6% for c2 and 27.8% vs 13.5% for C allele). Taken together, ADH3*2 and CYP2E1 c2/C alleles might independently contribute to the development of alcoholism in Mexican American men.

Seroepidemiología de la rubeola en mujeres mexicanas: encuesta nacional probabilística / Rubella seroepidemiologic in mexican women: a probabilistic inquiry

Se realizó un nuevo estudio seroepidemiológico de rubéola que incluye población rural, con el fin de ampliar y actualizar el conocimiento de la epidemiología de esta infección de nuestro país. Se estudiaron 24,331 sueros obtenidos durante 1987-1988, de mujeres entre 10 y 44 años de edad, distribuidas en las 32 entidades federativas del país, según lo descrito en el diseño conceptual y metodológico de la Encuesta Nacional Seroepidemiológica. La presencia de anticuerpos totales contra el virus de la rubeola se investigó mediante la técnica de inhibición de la hemaglutinación y se consideró positivo a todo suero con títulos de 1:8 o mayor. La frecuencia de mujeres seropositivas fue del 79.96 por ciento (IC de 95%, 79.5-80.5%), con incremento progresivo de acuerdo a la edad, desde 69.26 por ciento en las de 10 a 14 años hasta 87.84 por ciento en las de 40-44 años. En general, hubo menos seropositividad en la región sur del país y mayor en la región norte, además fue ligeramente mayor en el área urbana (82.4%) que en la rural (76.6%); con diferencia estadísticamente significativa en las menores de 14 años (74.7 contra 63.6%). En relación con el estrato socioeconómico, sólo se encontró diferencia al comparar el total del grupo económico alto (82.5%) contra el bajo (77%). Se observó, además, una tendencia significativa a incrementar la seropositividad a medida que aumentaba la escolaridad. Esta encuesta reveló una menor seropositividad para todos los grupos de edad, comparada con la encuesta serológica nacional de 1974, habiéndose incrementado la proporción de mujeres susceptibles, en particular las menores de 20 años. Este trabajo aporta información seroepidemiológica a nivel nacional y estatal que permitirá establecer políticas de vacunación sobre bases más sólidas.

A rubella seroepidemiologic survey was carried out in a rural population to better understand the epidemiology of this infections disease in México. 24 331 serum samples from women between 10 and 44 years old were collected during 1987- 1988 from the 32 federal states. Samples were tested for Rubella Antibodies by use of hemaggluti­nation inhibition with a titer 1:8 bring considered as posi­tive; 79.96 per cent (CI 95%, 7.5-80.5%) of women were seropositive, seropositivity increased with age, from 69.26 per cent in the age group of 10 to 14 years old, to 87.84 per cent in the 40-44 age group. Seropositivity rates were lower in southern states than in northerm states and, higher in urban areas that rural areas (82.4 vs 76.6%); statistical significative difference in seropositivity rates were fround between girls less than 14 years of age in urban areas as compared to rural areas (74.7 vs 63.6%). Seropositivity rates were related to socioeconomic status only when high status group were compared lower status group (82.5 vs 77%). In addition, we observed a signifi­cative trend of increasing resopositivity as level of school education increased. In comparison to the 1974 national survey, this seroepidemiological survey showed a de­creased seropositivity for all age groups, even with an increase in the number of susceptible women, particulary in the group less than 20 years old. This study offers seroepidemiologic information about rubella at a na­tional and regional level.

Prevalencia de anticuerpos para el virus de rubéola en mujeres gestantes de dos zonas del Valle de México / Prevalence of antibodies against rubella virus in pregnant women of two zones of the Valle de Mexico

El objetivo de esta investigación fue determinar el porcentaje de seropositividad en mujeres gestantes, para conocer la susceptibilidad a la infección por el virus de la rubéola. Se estudiaron 5535 mujeres embarazadas sanas del valle de México, entre los 15 y 44 años de edad. En cada una de ellas, se determinó la presencia de anticuerpos para el virus de la rubéola, utilizando el método de inhibición de la haglutinación. De 5535 casos, 92.6 por ciento tuvieron anticuerpos contra este agente viral, observándose que no hubo diferencias significativas en el porcentaje de seropositividad en los diferentes grupos de edad. La prevalencia de anticuerpos para rubéola en las gestantes por zona geográfica, fue de 92.4 por ciento para las derechohabientes de Iztapalapa y de 92.8 por ciento, las de Nezahualcóyotl. Los títulos de anticuerpos contra el virus de la rubéola que con más frecuencia se presentaron fueron de 1:16 (36.3 por ciento) y de 1:32 (29.6 por ciento). Se concluye que las mujeres derechohabientes en edad reproductiva de las áreas de Iztapalapa y Nezahualcóyotl, no justifican la vacunación masiva para el virus de la rubéola

Anticuerpos humorales y coproanticuerpos en ninos con gastroenteritis infecciosa causada por rotavirus. / Humoral antibodies and coproantibodies in children with infectious gastroenteritis caused by rotavirus

Se estudio la presencia de rotavirus en 93 ninos menores de seis meses de edad con gastroenteritis infecciosa aguda, por medio de la tecnica de electroforesis del RNA viral. Se encontro un 16.l por ciento de positividad. En los ninos que excretaron rotavirus, se buscaron anticuerpos inhibidores de la hemaglutinacion en los sueros pares; en todos ellos habia anticuerpos pero no hubo elevacion en la fase de convalescencia: los anticuerpos neutralizantes no fueron demonstrados en ninguno de los casos. En estos mismos ninos se buscaron coproanticuerpos tanto en la materia fecal obtenida en la fase aguda como en la de convalecencia; en siete casos se encontro seroconversion. Por los resultados obtenidos, la inmunidad humoral transmitida por la madre, aparentemente no protege de la infeccion por rotavirus, siendo de mayor importancia la inmunidad local

Prevalencia de marcadores serológicos para los virus B y C de la hepatitis en una cohorte de mujeres embarazadas del Valle de México / Prevalence of serologic markers for virus B and C hepatitis in a cohort of pregnant women from the valley of Mexico

Introducción. Una de las vías de trasmisión de los virus B (HVB) y C (HVC) de la hepatitis es la vertical o perinatal a través de una madre portadora de estos agentes. Material y métodos. En este estudio se investigaron por ELISA marcadores serológicos para HVB y HVC en 6254 gestantes sanas del Valle de México, con edades de 12 a 54 años. Resultados. Se detectó infección previa por HVB (anti-HBc+) en 114 casos (1.82 por ciento), con una P= 0.01 (1.35 vs 2.50 por ciento) entre gestantes de Ciudad Netzahualcóyotl y las del Intituto Nacional de Perinatología. De 6254 muestras, 0.03 por ciento (dos casos) fueron portadores de HVB (HBsAg+). Encontramos 2.7 por ciento (tres casos) positivos para anti HVC en 111 gestantes positivas para anti-HBc. Solamente seis casos (0.6 por ciento de 1000 embarazadas negativas para HVB presentaron anticuerpos contra HVC. Conclusiones. Se observó transmisión transplacentaria de anticuerpos contra virus B o C sin evidencia de infección en nueve de diez recién nacidos estudiados. La transmisión vertical o perinatal no es el principal mecanismo de diseminación de HVB y/o HVC en los grupos familiares analizados

Etiología de la hepatitis en la ciudad de México / Etiology of hepatitis in Mexico city

El objetivo fue conocer los agentes virales asociados con hepatitis aguda benigna, neonatal y postransfusional, investigando en 248 sueros, los anticuerpos totales e IgM para el virus de la hepatitis A, los antígenos s, e y los anticuerpos s, e y c del virus B de la hepatitis (RIA), así como la inmunoglobulina M por ELISA para los virus de la rubéola, citomegálico y herpes simples. De 222 casos con hepatitis aguda benigna, 89% correspondieron a hepatitis A y 5% al virus B. De 21 niños con hepatitis neonatal, en seis fue debida al virus A de la hepatitis y en uno al B. De cinco casos con hepatitis postransfusional, uno fue positivo para el virus A de la hepatitis y dos para el B. Encontramos 16 pacientes negativos a los virus A y B; de 13 con hepatitis aguda benigna, uno correspondió al virus citomegálico, cuatro a rubéola y ocho por exclusión a los virus NoA-NoB. De 14 niños con hepatitis neonatal, uno se debió a citomegalovirus y en 13 no se demostró etiología viral. En dos casos con hepatitis postransfusional, se consideró que el virus fue el NoA-NoB. Por los resultados obtenidos, se encontró que en la hepatitis aguda benigna y neonatal, el virus más frecuente fue el A y en la postransfusional los B y NoA-NoB

Prevalencia de marcadores serolórogicos para el virus de la hepatitis B en el hospital pediátrico / Prevalence of serological markers for hepatitis B among health care workers in a children's hospital

Se estudiaron 505 trabajadores de la salud en un hospital de Pediatría con el objeto de conocer la prevalencia de los marcadores serológicos para el virus de la hepatitis B. A los sueros se les determinó anticuerpos contra el antígeno "core" (Anti-HBc) y antígeno de superficie (HBsAg) mediante el método inmunoenzimático (EIA). A los que resultaron Anti-HBc positivos se les determinó anticuerpos contra el antígeno e (Anti-HBe) y anticuerpos contra el antígeno de superficie (HBsAg). Participaron 157 hombres y 348 mujeres con una antigüedad promedio en su trabajo de 9.05 años. Ninguno resultó positivo a HBsAg. Mediante la determinación de Anti-HBc hubo evidencia de exposición al VHB en 27 casos (5.34 por ciento); fueron a Anti-HBs 19 de 27 (70.3 por ciento) y a Anti-HBe 12 de 27 (44.4 por ciento). Se observó mayor riesgo a la infección en aquellas personas con historia de hapatitis y mayor tiempo de servicio profecional, particularmente los que trabajan en el área del laboratorio. Estos resultados muestran que la frecuencia de hepatitis B en el personal de unidades pediátricas resulta menor en comparación con el personal que atiende población adulta. Hepatitis B; seroprevalencia; personal de salud

Seroepidemiología de la infección por el virus A de la hepatitis en comunidades de la frontera sur del estado de Chiapas / Seroepidemiology of hepatitis A in communities on the Southern border of the state of Chiapas

Se investigó la epidemiología de la hepatitis A en la población guatemalteca y mexicana asentada en la frontera sur de México. Se estudiaron 1,127 sueros por medio del análisis inmunoenzimático, buscando anticuerpos totales contra el virus A de la hepatitis y la inmunoglobulina M específica en los niños menores de cinco años. De 764 sueros de guatemaltecos, 756 (98,9%) fueron positivos para la hepatitis A y 362 (99%) de 363 sueros de mexicanos. Se encontró una positividad del 100% en casi todos los grupos de edad, con un pequeño descenso porcentual para el grupo de uno a dos años de edad, en los guatemaltecos (87.8%) y los mexicanos (93.8%). La mediana de porcentajes de neutralización varió de 90 a 100% en los individuos seropositivos de ambas poblaciones. En 47 (25%) de 186 niños guatemaltecos y mexicanos menores de cinco años, se encontraron IgM contra el virus A de la hepatitis. Los resultados obtenidos indican que la infección por el virus A de la hepatitis es hiperendémica en la zona estudiada, que los niños adquieren esta infección en los primeros tres años de la vida y que la epidemiología de la hepatitis A entre los mexicanos no se modificó con la llegada de los refugiados guatemaltecos

Infection of pregnant women with hepatitis B and C viruses and risks for vertical transmission

Pregnant women infected with hepatitis B and C viruses pose a risk for infecting their newborn infants by vertical transmission. We studied 6,253 pregnant women aged 12-49 years for infection with hepatitis b (HBV) and C (HCV) viruses. Infection was diagnosed by measuring IgC antibodies against HBC, HBs, HBe, as well as IgM-HBc and HCV viral antigens with commercially avalible immunoassay kits. HBV infection was detected in 113 cases (1.8 percent), and prevalence was signficantly higher (2.4 percent) in a group of women with a high-risk pregnancy who were attending a perinatology hospital than in healthy pregnant women (1.67 percent, p<0.05). Infection with HBV was significantly higher in women older than 30 years old (p<0.05). HBsAg was found in blood, colostrum and vaginal exudate of two pregnant women; HBsAg was detected in the gastric aspirate but not in the blood of the two newborn infants. HBeAg and IgM-HBc were not detected in any of the smples. DNA-HBV was detected in serum of seven women, and DNA-HBV was detected in the gastric aspiratwe of only one of the newborns. HCV infection was diagnosed in three out of 111 women with markers for HBV infection (2.7 percent), and in 6 out of 1,000 women without these markers (0.6 percent). Anti-HCV antibodies were found in the serum of six of their infants during up to six months of age. Infants were monitored for one year and none of them developed any sign of hepatic disease. These results ksuggest that special attention should be paid to women older than 30 years and with a high-risk pregnanacy, as they are at a higher risk of HBV and HCB infections

Prevención de la hepatitis A / Prevention of hepatitis A

Entre las hepatitis virales agudas, la causada por el virus A (HVA) es tal vez la de mayor importancia debido a su alta frecuencia derivada de su mecanismo de transmisión fecal-oral. Clínicamente la hepatitis A es similar al resto de las hepatitis virales, sin embargo su aparición es más súbita, caracterizada por síntomas gripales y mialgias, dolor de cabeza y malestar general. Se autolimita en un lapso breve, aunque puede haber recaídas o colestásis prolongada al término de la fase aguda, ambas con carácter benigno. Su tasa de mortalidad es baja y nunca conduce a hepatitis crónica o a un estado de acarreador. La infección de individuos suceptibles puede ocurrir a cualquier edad. La prevención de la hepatitis por virus A debe planearse a nivel del saneamiento ambiental, de la correcta eliminación de las aguas negras y del cuidado en el riego de las legumbres. El mejoramiento de las condiciones socioeconómicas y de higiene, modifican los patrones epidemiológicos ya que a medida que disminuyen las infecciones en los niños, se incrementa la población adulta suceptible. La infección con el HVA da por resultado una inmunidad permanente, por lo que las reinfecciones son extraordinariamente infrecuentes. Existe la inmunización pasiva, inmunización activa, las vacunas inactivadas para HVA, vacunas atenuadas para HVA y se señalan otras opciones para la producción de vacunas contra HVA