Transcriptome Mining Provides Insights into Cell Wall Metabolism and Fiber Lignification in Agave tequilana Weber.

Resilience of growing in arid and semiarid regions and a high capacity of accumulating sugar-rich biomass with low lignin percentages have placed Agave species as an emerging bioenergy crop. Although transcriptome sequencing of fiber-producing agave species has been explored, molecular bases that control wall cell biogenesis and metabolism in agave species are still poorly understood. Here, through RNAseq data mining, we reconstructed the cellulose biosynthesis pathway and the phenylpropanoid route producing lignin monomers in A. tequilana, and evaluated their expression patterns in silico and experimentally. Most of the orthologs retrieved showed differential expression levels when they were analyzed in different tissues with contrasting cellulose and lignin accumulation. Phylogenetic and structural motif analyses of putative CESA and CAD proteins allowed to identify those potentially involved with secondary cell wall formation. RT-qPCR assays revealed enhanced expression levels of AtqCAD5 and AtqCESA7 in parenchyma cells associated with extraxylary fibers, suggesting a mechanism of formation of sclerenchyma fibers in Agave similar to that reported for xylem cells in model eudicots. Overall, our results provide a framework for understanding molecular bases underlying cell wall biogenesis in Agave species studying mechanisms involving in leaf fiber development in monocots.

Incremental levels of diagnostic information incentivize health-seeking in non-alcoholic fatty liver: a randomized clinical trial.

Patients with chronic disorders like non-alcoholic fatty liver disease (NAFLD) face important challenges adhering to diagnostic and treatment tracks. As NAFLD increases, the need to incentivize health-seeking behaviors grows. No evidence-based interventions to address this gap exist. The aim of the study was to estimate the effect of providing increasing levels of diagnostic information on medical care-seeking in adults newly diagnosed with NAFLD. We randomly assigned adults with a sonographic diagnosis of NAFLD at a check-up unit in Mexico to one of five groups. All groups received medical consultation. A: no further interventions; B: received multimedia educational material (MEM); C: MEM + NAFLD-fibrosis-score (NFS); D: MEM + transient elastography (TE); E: MEM + NFS + TE. 1209 participants were randomized, follow-up rate 91%; 82% male, BMI 30.5 ± 4 kg/m2. There were no differences in the proportion of patients undergoing further diagnostic evaluation of liver fibrosis (A 0.4%, E 0.4%, P-for-trend = 0.269). Groups who received more information sought specialized medical care more frequently: A 22%, E 30% (P-for-trend = 0.047). A trend to receive treatment was also observed at higher levels of information: A 26.7%, E 36.3% (P-for-trend = 0.134). Increasing the amount of diagnostic information seemed to increase patient's health-seeking. Tailoring the communication of information obtained for diagnosis could help to increase health-seeking in chronic disease patients.Trial registration: NCT01874249 (full date of first registration 11-06-2013).

Diagnostic and Neurological Overview of Brain Tuberculomas: A Review of Literature.

Tuberculosis is a disease caused by a bacteria named Mycobacterium tuberculosis (M. tb). It is estimated by World Health Organization (WHO) that nearly a quarter of the world's population is infected. Tuberculoma of the brain is one of the most severe extrapulmonary forms that affects patients younger than 40 years of age. Brain parenchymal tuberculoma develops in nearly one of 300 non-treated cases of pulmonary tuberculosis cases. In endemic regions, tuberculomas account for as many as 50% of all intracranial masses. Tuberculoma results in a hematogenous spread of M. tb from an extracranial source. Tuberculomas can mimic a variety of diseases and can present themselves in a subacute or chronic course, from asymptomatic to severe intracranial hypertension. Diagnosis is based on computed tomography (CT) scan and magnetic resonance imaging (MRI) studies with a similar ring-enhancing lesion. Treatment is primarily medical, and the duration for brain tuberculoma can vary from six to 36 months. In certain cases, surgery is recommended.

Acute COVID-19 Infection Associated With Necrotizing Disseminated Acute Leukoencephalopathy and Brain Microhemorrhages in a Pediatric Patient.

We present a case of a 14-year-old, previously healthy female, admitted with acute coronavirus disease 2019 infection and new-onset seizures secondary to virus-associated necrotizing disseminated acute leukoencephalopathy. Her symptoms resolved completely with intravenous immunoglobulin and steroids. Pathophysiology and prognosis of neurologic manifestations of coronavirus disease 2019 remain unclear.

Improved method for isolation of high-quality total RNA from Agave tequilana Weber roots.

Together with their undeniable role in the ecology of arid and semiarid ecosystems, Agave species are emerging as a model to dissect the relationships between crassulacean acid metabolism and high efficiency of light and water use, and as an energy crop for bioethanol production. Transcriptome resources from economically valuable Agaves species, such as Agave tequilana and A. salmiana, as well as hybrids for fibers, are now available, and multiple gene expression landscape analyses have been reported. Key components in molecular mechanisms underlying drought tolerance could be uncovered by analyzing gene expression patterns of roots. This study describes an efficient protocol for high-quality total RNA isolation from phenolic compounds-rich Agave roots. Our methodology involves suitable root handling and collecting in the field and using saving-time commercial kits available. RNA isolated from roots free of lignified out-layers and clean cortex showed high values of quality and integrity according to electrophoresis and microfluidics-based platform. Synthesis of long full-length cDNAs and PCR amplification tested the suitability for downstream applications of extracted RNA. The protocol was applied successfully to A. tequilana roots but can be used for other Agave species that also develop lignified epidermis/exodermis in roots.

Tomographic behavior of pneumonia caused by SARS-CoV-2.

BACKGROUND: From the first report of the respiratory disease caused by SARS-Cov-2 towards the end of 2019, in Wuhan, China, to June 8, 2020, 6,931,000 people had been affected in the world, and 113,619 in Mexico, where there is a lack of literature describing the tomographic behavior of this disease throughout its evolution and its correlation with patient clinical data. OBJECTIVE: To identify, describe and classify the manifestations detected on chest computed tomography images of patients with pneumonia caused by SARS-CoV-2. METHOD: Hospitalized patients with RT-PCR-confirmed SARS-CoV-2 infection and who underwent a plain chest tomography were included. RESULTS: The most common tomographic patterns were ground glass opacity, consolidation, cobblestone pattern and mixed pattern, with peripheral and subpleural distribution and bilateral involvement in up to 95 %. Subpleural bands that distorted the architecture were identified in up to 62 % of patients, with an average of seven days of evolution. The most common extrapulmonary finding was an increase in pulmonary artery transverse axis. CONCLUSION: Knowing the behavior of this type of pneumonia allows becoming familiarized with the characteristic tomographic patterns, in order to aid timely detection and treatment.

INTRODUCCIÓN: Desde el primer reporte de la enfermedad respiratoria causada por SARS-Cov-2 a finales de 2019, en Wuhan, China, hasta el 8 de junio de 2020, habían sido afectadas 6 931 000 personas en el mundo y 113 619 en México, donde se carece de informes que describan el comportamiento tomográfico de esta enfermedad a lo largo de su evolución y su correlación con los datos clínicos del paciente. OBJETIVO: Identificar, describir y clasificar las manifestaciones en las imágenes de tomografía de tórax de pacientes con neumonía causada por SARS-CoV-2. MÉTODO: Se incluyeron pacientes hospitalizados con infección por SARS-CoV-2 confirmada mediante PCR-TR y en quienes se realizó tomografía simple de tórax. RESULTADOS: Los patrones tomográficos más comunes fueron opacidad de vidrio despulido, consolidación, empedrado y patrón mixto, con distribución periférica, subpleural y afectación bilateral hasta en 95 %. Se identificaron bandas subpleurales que distorsionaban la arquitectura hasta en 62 % de los pacientes, con un promedio de siete días de evolución. El aumento del eje transverso de la arteria pulmonar constituyó el hallazgo extrapulmonar más frecuente. CONCLUSIÓN: Conocer el comportamiento de este tipo de neumonía permite la familiarización con los patrones tomográficos característicos, con el fin de coadyuvar a la detección y tratamiento oportunos.

Unravelling Chemical Composition of Agave Spines: News from Agave fourcroydes Lem.

Spines are key plant modifications developed to deal against herbivores; however, its physical structure and chemical composition have been little explored in plant species. Here, we took advantage of high-throughput chromatography to characterize chemical composition of Agave fourcroydes Lem. spines, a species traditionally used for fiber extraction. Analyses of structural carbohydrate showed that spines have lower cellulose content than leaf fibers (52 and 72%, respectively) but contain more than 2-fold the hemicellulose and 1.5-fold pectin. Xylose and galacturonic acid were enriched in spines compared to fibers. The total lignin content in spines was 1.5-fold higher than those found in fibers, with elevated levels of syringyl (S) and guaiacyl (G) subunits but similar S/G ratios within tissues. Metabolomic profiling based on accurate mass spectrometry revealed the presence of phenolic compounds including quercetin, kaempferol, (+)-catechin, and (-)-epicatechin in A. fourcroydes spines, which were also detected in situ in spines tissues and could be implicated in the color of these plants' structures. Abundance of (+)-catechins could also explain proanthocyanidins found in spines. Agave spines may become a plant model to obtain more insights about cellulose and lignin interactions and condensed tannin deposition, which is valuable knowledge for the bioenergy industry and development of naturally dyed fibers, respectively.

Comportamiento tomográfico de la neumonía causada por SARS-CoV-2 / Tomographic behavior of pneumonia caused by SARS-CoV-2

Resumen Introducción: Desde el primer reporte de la enfermedad respiratoria causada por SARS-Cov-2 a finales de 2019, en Wuhan, China, hasta el 8 de junio de 2020, habían sido afectadas 6 931 000 personas en el mundo y 113 619 en México, donde se carece de informes que describan el comportamiento tomográfico de esta enfermedad a lo largo de su evolución y su correlación con los datos clínicos del paciente. Objetivo: Identificar, describir y clasificar las manifestaciones en las imágenes de tomografía de tórax de pacientes con neumonía causada por SARS-CoV-2. Método: Se incluyeron pacientes hospitalizados con infección por SARS-CoV-2 confirmada mediante PCR-TR y en quienes se realizó tomografía simple de tórax. Resultados: Los patrones tomográficos más comunes fueron opacidad de vidrio despulido, consolidación, empedrado y patrón mixto, con distribución periférica, subpleural y afectación bilateral hasta en 95 %. Se identificaron bandas subpleurales que distorsionaban la arquitectura hasta en 62 % de los pacientes, con un promedio de siete días de evolución. El aumento del eje transverso de la arteria pulmonar constituyó el hallazgo extrapulmonar más frecuente. Conclusión: Conocer el comportamiento de este tipo de neumonía permite la familiarización con los patrones tomográficos característicos, con el fin de coadyuvar a la detección y tratamiento oportunos.

Abstract Background: From the first report of the respiratory disease caused by SARS-Cov-2 towards the end of 2019, in Wuhan, China, to June 8, 2020, 6,931,000 people had been affected in the world, and 113,619 in Mexico, where there is a lack of literature describing the tomographic behavior of this disease throughout its evolution and its correlation with patient clinical data. Objective: To identify, describe and classify the manifestations detected on chest computed tomography images of patients with pneumonia caused by SARS-CoV-2. Method: Hospitalized patients with RT-PCR-confirmed SARS-CoV-2 infection and who underwent a plain chest tomography were included. Results: The most common tomographic patterns were ground glass opacity, consolidation, cobblestone pattern and mixed pattern, with peripheral and subpleural distribution and bilateral involvement in up to 95 %. Subpleural bands that distorted the architecture were identified in up to 62 % of patients, with an average of seven days of evolution. The most common extrapulmonary finding was an increase in pulmonary artery transverse axis. Conclusion: Knowing the behavior of this type of pneumonia allows becoming familiarized with the characteristic tomographic patterns, in order to aid timely detection and treatment.

Thrombosis of the Portal Venous System in Cirrhotic vs. Non-Cirrhotic Patients.

INTRODUCTION AND AIM: Thrombosis is a vascular disorder of the liver often associated with significant morbidity and mortality. Cirrhosis is a predisposing factor for portal venous system thrombosis. The aim of this study is to determine differences between cirrhotics and non-cirrhotics that develop thrombosis in portal venous system and to evaluate if cirrhosis severity is related to the development of portal venous system thrombosis. MATERIAL AND METHODS: We studied patients diagnosed with portal venous system thrombosis using contrast-enhanced computed tomography scan and doppler ultrasound at Medica Sur Hospital from 2012 to 2017. They were categorized into two groups; cirrhotics and non-cirrhotics. We assessed the hepatic function by Child-Pugh score and model for end-stage liver disease. RESULTS: 67 patients with portal venous system thrombosis (25 with non-cirrhotic liver and 42 with cirrhosis) were included. The mean age (± SD) was 65 ± 9.5 years in cirrhotic group and 57 ± 13.2 years (p = 0.009) in non-cirrhotic group. Comparing non-cirrhotics and cirrhotics, 8 non-cirrhotic patients showed evidence of extra-hepatic inflammatory conditions, while in the cirrhotic group no inflammatory conditions were found (p < 0.001). 27 (64.29%) cirrhotic patients had thrombosis in the portal vein, while only 9 cases (36%) were found in non-cirrhotics (p = 0.02). CONCLUSIONS: In cirrhotic patients, hepatocellular carcinoma and cirrhosis were the strongest risk factors to develop portal venous system thrombosis. In contrast, extrahepatic inflammatory conditions were main risk factors associated in non-cirrhotics. Moreover, the portal vein was the most frequent site of thrombosis in both groups.

Both alcoholic and non-alcoholic steatohepatitis association with cardiovascular risk and liver fibrosis.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is the most common cause of liver disease worldwide. Mortality in NAFLD is mainly related to cardiovascular disease (CVD) and cancer. NAFLD and its association with both CVD and liver disease risk have been well evaluated, but the association of NAFLD with alcohol, known as "both alcoholic and non-alcoholic steatohepatitis" (BASH), remains uncertain. The objective of this study was to assess the influence of alcohol and obesity in the development of liver and cardiovascular disease risk. METHODS: This was a case-control study that included patients from a regular check-up. Alcohol consumption was evaluated with MAST, AUDIT, and CAGE. Cardiovascular risk was evaluated using the Framingham score, and liver fibrosis was evaluated with APRI and NAFLD score. Patients were classified in five groups: healthy patients, steatosis with obesity, steatosis with alcoholism, BASH, and idiopathic steatosis. RESULTS: A total of 414 patients were included. The BASH group represented 16% of patients, and showed a greater proportion of patients with high cardiovascular risk with 17% (p = 0.001), and liver fibrosis with 9%, according to the APRI score (p = 0.10). A multivariate logistic regression showed that alcohol consumption >140 g/week (OR 2.546, 95% CI 1.11-5.81, p = 0.003) and BMI >25 kg/m2 (OR 12.64, 95% CI 1.66 96.20, p = 0.001) were related to high cardiovascular risk. Liver fibrosis according to APRI was only related to alcohol consumption >140 g/week (OR 2.74, 95% CI 1-7.48, p = 0.03). CONCLUSIONS: BASH remains an area not well explored, and of great implication given the increasing number of patients affected. We observed an additive effect of both etiologies in the development of high cardiovascular and liver disease risk.

Age and regional differences in clinical presentation and risk of hospitalization for dengue in Brazil, 2000-2014.

OBJECTIVES: Dengue cases range from asymptomatic to severe, eventually leading to hospitalization and death. Timely and appropriate management is critical to reduce morbidity. Since 1980, dengue has spread throughout Brazil, affecting an increasing number of individuals. This paper describes age and regional differences in dengue's clinical presentation and associated risk of hospitalization based on more than 5 million cases reported to the Brazilian Ministry of Health from 2000-2014. METHODS: We performed a retrospective analysis of ∼5,450,000 dengue cases, relating clinical manifestations and the risk of hospitalization to age, gender, previous infection by dengue, dengue virus serotype, years of formal education, delay to first attendance and the occurrence of dengue during outbreaks and in different Brazilian regions. RESULTS: Complicated forms of dengue occurred more frequently among those younger than 10 years (3.12% vs 1.92%) and those with dengue virus 2 infection (7.65% vs 2.42%), with a delay to first attendance >2 days (3.18% vs 0.82%) and with ≤4 years of formal education (2.02% vs 1.46%). The risk of hospitalization was higher among those aged 6-10 years old (OR 4.57; 95% CI 1.43-29.96) and those who were infected by dengue virus 2 (OR 6.36; 95% CI 2.52-16.06), who lived in the Northeast region (OR 1.38; 95% CI 1.11-2.10) and who delayed first attendance by >5 days (composite OR 3.15; 95% CI 1.33-8.9). CONCLUSIONS: In Brazil, the occurrence of severe dengue and related hospitalization is associated with being younger than 10 years old, being infected by dengue virus 2 or 3, living in the Northeast region (the poorest and the second most populated) and delaying first attendance for more than 2 days.

Age and regional differences in clinical presentation and risk of hospitalization for dengue in Brazil, 2000-2014

OBJECTIVES: Dengue cases range from asymptomatic to severe, eventually leading to hospitalization and death. Timely and appropriate management is critical to reduce morbidity. Since 1980, dengue has spread throughout Brazil, affecting an increasing number of individuals. This paper describes age and regional differences in dengue’s clinical presentation and associated risk of hospitalization based on more than 5 million cases reported to the Brazilian Ministry of Health from 2000-2014. METHODS: We performed a retrospective analysis of ∼5,450,000 dengue cases, relating clinical manifestations and the risk of hospitalization to age, gender, previous infection by dengue, dengue virus serotype, years of formal education, delay to first attendance and the occurrence of dengue during outbreaks and in different Brazilian regions. RESULTS: Complicated forms of dengue occurred more frequently among those younger than 10 years (3.12% vs 1.92%) and those with dengue virus 2 infection (7.65% vs 2.42%), with a delay to first attendance >2 days (3.18% vs 0.82%) and with ≤4 years of formal education (2.02% vs 1.46%). The risk of hospitalization was higher among those aged 6-10 years old (OR 4.57; 95% CI 1.43-29.96) and those who were infected by dengue virus 2 (OR 6.36; 95% CI 2.52-16.06), who lived in the Northeast region (OR 1.38; 95% CI 1.11-2.10) and who delayed first attendance by >5 days (composite OR 3.15; 95% CI 1.33-8.9). CONCLUSIONS: In Brazil, the occurrence of severe dengue and related hospitalization is associated with being younger than 10 years old, being infected by dengue virus 2 or 3, living in the Northeast region (the poorest and the second most populated) and delaying first attendance for more than 2 days.

Paraconsistents artificial neural networks applied to the study of mutational patterns of the F subtype of the viral strains of HIV-1 to antiretroviral therapy.

The high variability of HIV-1 as well as the lack of efficient repair mechanisms during the stages of viral replication, contribute to the rapid emergence of HIV-1 strains resistant to antiretroviral drugs. The selective pressure exerted by the drug leads to fixation of mutations capable of imparting varying degrees of resistance. The presence of these mutations is one of the most important factors in the failure of therapeutic response to medications. Thus, it is of critical to understand the resistance patterns and mechanisms associated with them, allowing the choice of an appropriate therapeutic scheme, which considers the frequency, and other characteristics of mutations. Utilizing Paraconsistents Artificial Neural Networks, seated in Paraconsistent Annotated Logic Et which has the capability of measuring uncertainties and inconsistencies, we have achieved levels of agreement above 90% when compared to the methodology proposed with the current methodology used to classify HIV-1 subtypes. The results demonstrate that Paraconsistents Artificial Neural Networks can serve as a promising tool of analysis.

Evaluation of environmental genotoxicity by comet assay in Columba livia.

The concentrations of recognized or suspected genotoxic and carcinogenic agents found in the air of large cities and, in particular, developing countries, have raised concerns about the potential for chronic health effects in the populations exposed to them. The biomonitoring of environmental genotoxicity requires the selection of representative organisms as "sentinels," as well as the development of suitable and sensitive assays, such as those aimed at assessing DNA damage. The aim of this study was to evaluate DNA damage levels in erythrocytes from Columba livia living in the metropolitan area of Monterrey, Mexico, compared with control animals via comet assay, and to confirm the results via Micronuclei test (MN) and DNA breakage detection-fluorescence in situ hybridization (DBD-FISH). Our results showed a significant increase in DNA migration in animals from the area assayed compared with that observed in control animals sampled in non-contaminated areas. These results were confirmed by MN test and DBD-FISH. In conclusion, these observations confirm that the examination of erythrocytes from Columba livia via alkaline comet assay provides a sensitive and reliable end point for the detection of environmental genotoxicants.

Acido folico y su relación con malformaciones por defectos de cierre tubo neural / Folic Acid and its relationship to malformations due to neural tube closure defects

En la presente revisión bibliográfica se hace referencia del ácido fólico, vitamina perteneciente al complejo B,cuya ingestión en etapa preconcepcional contribuye a la prevención de defectos congénitos y otros problemas relacionados con la salud del ser humano. El Ácido Fólico (AF) es necesario para la formación de proteínas estructurales y hemoglobina. La deficiencia de AF es la condición en que cuerpo carece de reservas adecuadas de vitamina B9. Durante toda la gestación se debe ingerir AF, debido al continuo proceso de crecimiento y desarrollo del embrión y feto, donde el AF participa en la metilación del ADN, proceso imprescindible para la constante división y crecimiento celular. El cierre de neuroporos del tubo neural ocurre antes que finalice el primer mes de embarazo. Cuando la mujer se da cuenta que está embarazada, las consecuencias de una dieta deficiente en AF ya habrán mostrado sus consecuencias, provocando varias deformaciones congénitas denominadas malformaciones por Defectos de cierre del Tubo Neural (DTN). La ingesta de AF debe recomendarse en toda la vida reproductiva de la mujer (pubertad-antes de menopausia), esto evita el aumento de la homocisteína; productor importante de DTN...

A mathematical model for optimizing the indications of liver transplantation in patients with hepatocellular carcinoma.

BACKGROUND: The criteria for organ sharing has developed a system that prioritizes liver transplantation (LT) for patients with hepatocellular carcinoma (HCC) who have the highest risk of wait-list mortality. In some countries this model allows patients only within the Milan Criteria (MC, defined by the presence of a single nodule up to 5 cm, up to three nodules none larger than 3 cm, with no evidence of extrahepatic spread or macrovascular invasion) to be evaluated for liver transplantation. This police implies that some patients with HCC slightly more advanced than those allowed by the current strict selection criteria will be excluded, even though LT for these patients might be associated with acceptable long-term outcomes. METHODS: We propose a mathematical approach to study the consequences of relaxing the MC for patients with HCC that do not comply with the current rules for inclusion in the transplantation candidate list. We consider overall 5-years survival rates compatible with the ones reported in the literature. We calculate the best strategy that would minimize the total mortality of the affected population, that is, the total number of people in both groups of HCC patients that die after 5 years of the implementation of the strategy, either by post-transplantation death or by death due to the basic HCC. We illustrate the above analysis with a simulation of a theoretical population of 1,500 HCC patients with tumor size exponentially. The parameter λ obtained from the literature was equal to 0.3. As the total number of patients in these real samples was 327 patients, this implied in an average size of 3.3 cm and a 95% confidence interval of [2.9; 3.7]. The total number of available livers to be grafted was assumed to be 500. RESULTS: With 1500 patients in the waiting list and 500 grafts available we simulated the total number of deaths in both transplanted and non-transplanted HCC patients after 5 years as a function of the tumor size of transplanted patients. The total number of deaths drops down monotonically with tumor size, reaching a minimum at size equals to 7 cm, increasing from thereafter. With tumor size equals to 10 cm the total mortality is equal to the 5 cm threshold of the Milan criteria. CONCLUSION: We concluded that it is possible to include patients with tumor size up to 10 cm without increasing the total mortality of this population.

Determination of foscarnet (trisodium phosphonoformate) in pharmaceutical preparations by high-performance liquid chromatography with ultraviolet detection.

An isocratic high-performance liquid chromatographic method with UV detection has been developed and validated for the quantitative determination of foscarnet in isoosmotic sodium chloride aqueous solution. The mobile phase consisted of mixture of methanol:water (30:70 v/v), containing 1 mm tetrahexylammonium hydrogen sulphate at pH 5.80. The analyte was separated on a reversed-phase C(18) column packed with 4 microm spherical particles of octadecylsilane. Hydrochlorothiazide was used as internal standard. UV detection at 232 nm allowed a quantification limit of 50 microg/mL. The assay was linear from 50 to 4000 microg/mL. The coefficient of variation was < or =2.52% for intra-assay precision and < or =3.49% for inter-assay precision. The deviation from the nominal value ranged from -0.57 to 0.47% for the same-day accuracy and from -0.75 to 3.06% for day-to-day accuracy.

Forecasting versus projection models in epidemiology: the case of the SARS epidemics.

In this work we propose a simple mathematical model for the analysis of the impact of control measures against an emerging infection, namely, the severe acute respiratory syndrome (SARS). The model provides a testable hypothesis by considering a dynamical equation for the contact parameter, which drops exponentially with time, simulating control measures. We discuss the role of modelling in public health and we analyse the distinction between forecasting and projection models as assessing tools for the estimation of the impact of intervention strategies. The model is applied to the communities of Hong Kong and Toronto (Canada) and it mimics those epidemics with fairly good accuracy. The estimated values for the basic reproduction number, R0, were 1.2 for Hong Kong and 1.32 for Toronto (Canada). The model projects that, in the absence of control, the final number of cases would be 320,000 in Hong Kong and 36,900 in Toronto (Canada). In contrast, with control measures, which reduce the contact rate to about 25% of its initial value, the expected final number of cases is reduced to 1778 in Hong Kong and 226 in Toronto (Canada). Although SARS can be a devastating infection, early recognition, prompt isolation, and appropriate precaution measures, can be very effective to limit its spread.