Potential effect of using ABO-compatible living-donor liver transplantation

Liver transplantation increased 1.84-fold from 1988 to 2004. However, the number of patients on the waiting list for a liver increased 2.71-fold, from 553 to 1500. We used a mathematical equation to analyze the potential effect of using ABO-compatible living-donor liver transplantation (LDLT) on both our liver transplantation program and the waiting list. We calculated the prevalence distribution of blood groups (O, A, B, and AB) in the population and the probability of having a compatible parent or sibling for LDLT. The incidence of ABO compatibility in the overall population was as follows: A, 0.31; B, 0.133; O, 0.512; and AB, 0.04. The ABO compatibility for parent donors was blood group A, 0.174; B, 0.06; O, 0.152; and AB, 0.03; and for sibling donors was A, 0.121; B, 0.05; O, 0.354; and AB, 0.03. Use of LDLT can reduce the pressure on our liver transplantation waiting list by decreasing its size by at least 16.5% at 20 years after its introduction. Such a program could save an estimated 3600 lives over the same period.

Estimation of R0 from the initial phase of an outbreak of a vector-borne infection

The magnitude of the basic reproduction ratio R(0) of an epidemic can be estimated in several ways, namely, from the final size of the epidemic, from the average age at first infection, or from the initial growth phase of the outbreak. In this paper, we discuss this last method for estimating R(0) for vector-borne infections. Implicit in these models is the assumption that there is an exponential phase of the outbreaks, which implies that in all cases R(0)>1. We demonstrate that an outbreak is possible, even in cases where R(0) is less than one, provided that the vector-to-human component of R(0) is greater than one and that a certain number of infected vectors are introduced into the affected population. This theory is applied to two real epidemiological dengue situations in the southeastern part of Brazil, one where R(0) is less than one, and other one where R(0) is greater than one. In both cases, the model mirrors the real situations with reasonable accuracy.

The tempo and mode of evolution of transposable elements as revealed by molecular phylogenies reconstructed from mosquito genomes

Although many mathematical models exist predicting the dynamics of transposable elements (TEs), there is a lack of available empirical data to validate these models and inherent assumptions. Genomes can provide a snapshot of several TE families in a single organism, and these could have their demographics inferred by coalescent analysis, allowing for the testing of theories on TE amplification dynamics. Using the available genomes of the mosquitoes Aedes aegypti and Anopheles gambiae, we indicate that such an approach is feasible. Our analysis follows four steps: (1) mining the two mosquito genomes currently available in search of TE families; (2) fitting, to selected families found in (1), a phylogeny tree under the general time-reversible (GTR) nucleotide substitution model with an uncorrelated lognormal (UCLN) relaxed clock and a nonparametric demographic model; (3) fitting a nonparametric coalescent model to the tree generated in (2); and (4) fitting parametric models motivated by ecological theories to the curve generated in (3).

Spatio-temporal tracking and phylodynamics of an urban dengue 3 outbreak in São Paulo, Brazil

The dengue virus has a single-stranded positive-sense RNA genome of ∼10.700 nucleotides with a single open reading frame that encodes three structural (C, prM, and E) and seven nonstructural (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) proteins. It possesses four antigenically distinct serotypes (DENV 1–4). Many phylogenetic studies address particularities of the different serotypes using convenience samples that are not conducive to a spatio-temporal analysis in a single urban setting. We describe the pattern of spread of distinct lineages of DENV-3 circulating in São José do Rio Preto, Brazil, during 2006. Blood samples from patients presenting dengue-like symptoms were collected for DENV testing. We performed M-N-PCR using primers based on NS5 for virus detection and identification. The fragments were purified from PCR mixtures and sequenced. The positive dengue cases were geo-coded. To type the sequenced samples, 52 reference sequences were aligned. The dataset generated was used for iterative phylogenetic reconstruction with the maximum likelihood criterion. The best demographic model, the rate of growth, rate of evolutionary change, and Time to Most Recent Common Ancestor (TMRCA) were estimated. The basic reproductive rate during the epidemics was estimated. We obtained sequences from 82 patients among 174 blood samples. We were able to geo-code 46 sequences. The alignment generated a 399-nucleotide-long dataset with 134 taxa. The phylogenetic analysis indicated that all samples were of DENV-3 and related to strains circulating on the isle of Martinique in 2000–2001. Sixty DENV-3 from São José do Rio Preto formed a monophyletic group (lineage 1), closely related to the remaining 22 isolates (lineage 2). We assumed that these lineages appeared before 2006 in different occasions. By transforming the inferred exponential growth rates into the basic reproductive rate, we obtained values for lineage 1 of R₀ = 1.53 and values for lineage 2 of R₀ = 1.13. Under the exponential model, TMRCA of lineage 1 dated 1 year and lineage 2 dated 3.4 years before the last sampling. The possibility of inferring the spatio-temporal dynamics from genetic data has been generally little explored, and it may shed light on DENV circulation. The use of both geographic and temporally structured phylogenetic data provided a detailed view on the spread of at least two dengue viral strains in a populated urban area.

Most of the molecular phylogeny studies of dengue fever, an important public health problem, use convenience samples for their analysis, and they do not evaluate the spatial and temporal features involved in the spread of the different serotypes (and genotypes) circulating in urban settings during an outbreak. Our study describes the patterns of spread of different lineages of dengue 3 virus circulating in a medium-sized city from Brazil, and we also analyzed the dynamics and microevolution of the disease during the 2006 outbreak. We used both geographic and temporally structured phylogenetic data, which provided a relatively detailed view on the spread of at least two dengue viral lineages circulating in an urban area. The pattern of dengue virus circulation might be similar to many other settings all over the world, and the information provided by our study can help a better understanding of dengue outbreaks, providing important information for public-health systems. We could identify at least two lineages, which were introduced in different occasions. They circulated and spread at different rates within the city, and this differential spread and the role of socioeconomic features in this phenomenon are discussed.

Risk estimates of dengue in travelers to dengue endemic areas using mathematical models

BACKGROUND

Dengue has emerged as a frequent problem in international travelers. The risk depends on destination, duration, and season of travel. However, data to quantify the true risk for travelers to acquire dengue are lacking.

METHODS

We used mathematical models to estimate the risk of nonimmune persons to acquire dengue when traveling to Singapore. From the force of infection, we calculated the risk of dengue dependent on duration of stay and season of arrival.

RESULTS

Our data highlight that the risk for nonimmune travelers to acquire dengue in Singapore is substantial but varies greatly with seasons and epidemic cycles. For instance, for a traveler who stays in Singapore for 1 week during the high dengue season in 2005, the risk of acquiring dengue was 0.17%, but it was only 0.00423% during the low season in a nonepidemic year such as 2002.

DISCUSSION

Risk estimates based on mathematical modeling will help the travel medicine provider give better evidence-based advice for travelers to dengue endemic countries.

Dynamics of the 2006/2007 dengue outbreak in Brazil

We analyzed dengue incidence in the period between October 2006-July 2007 of 146 cities around the country were Larval Index Rapid Assay (LIRA) surveillance was carried out in October 2006. Of these, we chosen 61 cities that had 500 or more cases reported during this period. We calculated the incidence coefficient, the force of infection (lambda) and the basic reproduction number (R0) of dengue in those 61 cities and correlated those variables with the LIRA. We concluded that lambda and R0 are more associated with the number of cases than LIRA. In addition, the average R0 for the 2006/2007 dengue season was almost as high as that calculated for the 2001/2002 season, the worst in Brazilian history.

Threat of dengue to blood safety in dengue-endemic countries

Modeling the risk for transmission of this disease is quantified by blood transfusions.

Dengue, the most common arbovirus infection globally, is transmitted by mosquito vectors. Healthcare-related transmission, including transmission by blood products, has been documented, although the frequency of these occurrences is unknown. Dengue is endemic to Singapore, a city-state in Asia. Using mathematical modeling, we estimated the risk for dengue-infected blood transfusions in Singapore in 2005 to be 1.625–6/10,000 blood transfusions, assuming a ratio of asymptomatic to symptomatic infections of 2:1 to 10:1. However, the level of viremia required to cause clinical dengue cases is person-dependent and unknown. Further studies are needed to establish the magnitude of the threat that dengue poses to blood safety in countries where it is endemic. It will then be possible after this information is obtained to assess whether screening is feasible and to identify approaches that are most cost-effective on the basis of characteristics of local populations and seasonality of dengue.

Sexual harassment in the physician-patient interaction: analysis of charges against doctors in the state of São Paulo

OBJECTIVE

This research intends to discuss sexual harassment within the doctor-patient relationship based on four parameters: doctor's characteristics, accuser's characteristics, accusation characteristics, and the evaluation by the Medicine Council of São Paulo.

METHOD

It is a descriptive, quantitative approach using a retrospective documental analysis. Studied subjects were doctors who were allegedly engaged in sexual harassment. This analysis considered all accusations made from January 2000 to December 2005 (n=150).

RESULTS

For this type of sexual abuse, there was a prevalence of male professionals (96.6%) who committed abuse against female patients (90.3%) during adulthood (77.7%). The mean age of the accused was 46.87 years, ranging from 30-76 years, concentrated between 46-75 years. The intrinsic difficulty of understanding sexual harassment by a professional constrained ethical evaluation of the cases, with 24.1% of the cases being considered proceeding charges by the professional council. When the cases were recognized as proceeding, they were either filed (88.2%) or were considered to be ethical infringement (11.8%) becoming Professional Ethical Process (PEP). In the majority of proceeding cases (87%), there was a Police Occurrence Report enclosed.

DISCUSSION AND CONCLUSION

The incidence of sexual abuse by professionals was independent of education, as the accused professionals came from a large variety of medical colleges, without significant differences related to institution. The predominance of accusations against older professionals may occur due to the frail personality structure that allows professional acting out. Objective evidence is very important in ethical evaluations compared to psychological and subjective evidence.

Pontos positivos e negativos observados em uma experiência prática com pares educativos em prevenção de aids numa escola secundária em São Paulo, Brasil

<span style="font-family: HelveticaLTStd-Roman; font-size: xx-small;"><span style="font-family: HelveticaLTStd-Roman; font-size: xx-small;"><p>Pares educativos são uma importante ferramenta educativa utilizada internacionalmente com boas avaliações na eficácia. O presente estudo tem por objetivo avaliar o processo de implantação de pares educativos como programa de prevenção em uma escola modelo da periferia de São Paulo, com alunos de ensino médio, no período de 2003 a 2004. O trabalho foi aplicado em fases: identificação dos principais problemas frente à epidemia HIV/aids naquela escola, elaboração e aplicação de um questionário em 115 alunos e realização de quatro oficinas de sexo seguro. Na implantação desse processo foram destacados os principais pontos positivos e negativos. Como pontos positivos destacaram-se: elaboração do questionário, aceitação de materiais didáticos utilizados nas oficinas. Como pontos negativos destacaram-se: resistência da escola impondo limites no processo; obstrução na inserção do problema principal desta escola no questionário, indicação dos pares educativos e falta de tempo dos funcionários.</p></span></span>

The potential impact of using donations after cardiac death on the liver transplantation program and waiting list in the state of Sao Paulo, Brazil

Liver transplantation was first performed at the University of Sao Paulo School of Medicine in 1968. Since then, the patient waiting list for liver transplantation has increased at a rate of 150 new cases per month. Liver transplantation itself rose 1.84-fold (from 160 to 295) from 1988 to 2004. However, the number of patients on the liver waiting list jumped 2.71-fold (from 553 to 1500). Consequently, the number of deaths on the liver waiting list moved to a higher level, from 321 to 671, increasing 2.09-fold. We have applied a mathematical model to analyze the potential impact of using a donation after cardiac death (DCD) policy on our liver transplantation program and on the waiting list. Five thousand one hundred people died because of accidents and other violent causes in our state in 2004; of these, only 295 were donors of liver grafts that were transplanted. The model assumed that 5% of these grafts would have been DCD. We found a relative reduction of 27% in the size of the liver transplantation waiting list if DCD had been used by assuming that 248 additional liver transplants would have been performed annually. In conclusion, the use of DCD in our transplantation program would reduce the pressure on our liver transplantation waiting list, reducing it by at least 27%. On the basis of this model, the projected number of averted deaths is about 41,487 in the next 20 years.

The many faces of epidemiology: evolutionary epidemiology

We review important issues revealed by the application of the evolutionary theory to epidemiological problems. The scope is restricted to infectious diseases and the evolution of virulence as a consequence of public health strategies to control transmission. We focus on the discussion about the possibility of virulence management and explore current scenarios in which recent advances in molecular biology and genetics offer new tools to monitor and change diversity among pathogens, vertebrate and invertebrate hosts. We stress the need to integrate the analytical framework of epidemiology into population genetics and evolutionary theory. We anticipate as an outcome of this process the development of study designs and analytical tools to predict the evolutionary implications of control measures in the population and surveillance mechanisms to continuously monitor the changes in pathogen virulence patterns. Communication among modelers, epidemiologists and molecular biologists is essential in order to design model-driven field trials and to develop data-driven analytical tools leading to conclusive findings that can inform the public health oriented decision making process.

Vaccinating the vampire bat Desmodus rotundus against rabies

The objective of this study was to extend the previous work of indirect oral rabies immunization of vampire bats (Desmodus rotundus) maintained in captivity, which demonstrated the immunogenicity of the V-RG vaccine (Vaccinia-Rabies Glycoprotein) and indicated that although the results had been encouraging, a new method for concentrating the vaccine should be tested in order to avoid vaccine loss and increase the survival proportion of bats after rabies challenge. In this study, three groups of seven bats each were tested with vaccine concentrated by ultrafiltration through a cellulose membrane. The vaccine was homogenized in Vaseline paste and applied to the back of one vector bat, which was then reintroduced into its group. A dose of 10(5.0) MICLD(50) rabies virus was used by intramuscular route to challenge the bats postvaccination. The survival proportion in the three groups after the challenge was 71.4%, 71.4% and 100%.

The elimination of Chagas' disease from Brazil

On 9 June 2006 the Pan American Health Organization (PAHO) presented the Minister of Health of Brazil with the International Elimination of Transmission of Chagas' Disease Certificate. This act was the culmination of an intensive process that began in 1991 with the Southern Cone Initiative, a joint agreement between the governments of Argentina, Bolivia, Brazil, Chile, Paraguay, Uruguay and Peru, to control Chagas' disease by the elimination of the main vector, Triatoma infestans. This initiative has been highly successful and the prevalence area of the vector diminished rapidly in the last years. As a consequence, the current seroprevalence in children aged between 0 and 5 years is of the order of 10(-5), a clear indication that transmission, if it is occurring, is only accidental. In this review I calculate the basic reproduction number, R0, for Chagas' disease and demonstrate that its relatively low value (1.25) explains why vectorial transmission was interrupted relatively easily. In addition, I used a mathematical model to forecast how long the remaining cases of the disease, as well as the additional vertically transmitted cases will last.

HIV infection and related risk behaviors in a community of recyclable waste collectors of Santos, Brazil

OBJECTIVE

To estimate the seroprevalence of HIV, hepatitis B and C and syphilis and to describe risk behaviors associated to their transmission among recyclable waste collectors.

METHODS

A seroepidemiological survey was carried out in the city of Santos, Southeastern Brazil, in 2005. A total of 315 individuals were enrolled in the survey, of which 253 subjects underwent serological testing HIV, hepatitis B and C and syphilis. Statistical analysis consisted of univariate and bivariate analyses (cross-tabulation and odds ratio) and multivariate analysis (by logistic regression), relating HIV infection with established risk behaviors and seropositivity.

RESULTS

Overall seroprevalences were: HIV, 8.9%; hepatitis B, 34.4%; hepatitis C, 12.4%; and syphilis, 18.4%. Subjects were characterized by a predominance of males with low educational and economic levels, subjected to parenteral and sexual exposures to HIV and other sexually transmitted infections. Multivariate analysis results indicated that risk factors for both sexually and parenterally related exposure were significantly associated with HIV in this community.

CONCLUSIONS

Seroprevalences found in the study were approximately 10 to 12 times higher than the national average. These communities are socially marginalized and generally not recognized by national programs as potentially endangered populations.

The risk of chikungunya fever in a dengue-endemic area

BACKGROUND

Chikungunya, an alphavirus of the Togaviridae family, causes a febrile disease transmitted to humans by the bite of infected Aedes mosquitoes. This infection is reaching endemic levels in many Southeast Asian countries. Symptoms include sudden onset of fever, chills, headache, nausea, vomiting, joint pain with or without swelling, low back pain, and rash. According to the World Health Organization, there are 2 billion people living in Aedes-infested areas. In addition, traveling to these areas is popular, making the potential risk of infections transmitted by the bite of infected Aedes mosquitoes very high.

METHODS

We proposed a mathematical model to estimate the risk of acquiring chikungunya fever in an Aedes-infested area by taking the prevalence of dengue fever into account. The basic reproduction number for chikungunya fever R(0chik) can be written as a function of the basic reproduction number of dengue R(0dengue) by calculating the ratio R(0chik)/R(0dengue). From R(0chik), we estimated the force of infection and the risk of acquiring the disease both for local residents of a dengue-endemic area and for travelers to this area.

RESULTS

We calculated that R(0chik) is 64.4% that of R(0dengue). The model was applied to a hypothetical situation, namely, estimating the individual risk of acquiring chikungunya fever in a dengue-endemic area, both for local inhabitants (22% in steady state) and for visiting travelers (from 0.31% to 1.23% depending on the time spent in the area).

CONCLUSIONS

The method proposed based on the output of a dynamical model is innovative and provided an estimation of the risk of infection, both for local inhabitants and for visiting travelers.

Boosting virology in Brazil

The Viral Genetic Diversity Network, established in Brazil to enhance the study of viruses, antiviral drug resistance, and the spread of specific viral genotypes, also increased the net scientific production of virology research, and may provide a viable model for other developing countries to reduce the risks of pandemics and facilitate basic scientific research.

Factors affecting compliance with the measles vaccination schedule in a Brazilian city

CONTEXT AND OBJECTIVE

The success of vaccination campaigns depends on the degree of adherence to immunization initiatives and schedules. Risk factors associated with children's failure to receive the measles vaccine at the correct age were studied in the city of São Paulo, Brazil.

DESIGN AND SETTING

Case-control and exploratory study, in the metropolitan area of São Paulo.

METHODS

The caregivers of 122 children were interviewed regarding their perceptions and understanding about the measles vaccination and the disease.

RESULTS

The results showed that age, region of residence, marital status and education level were unrelated to taking measles vaccines adequately. Most individuals remembered being informed about the last annual vaccination campaign by television, but no communication channel was significantly associated with vaccination status. The answers to questions about knowledge of the disease or the vaccine, when analyzed alone, were not associated with taking measles vaccinations at the time indicated by health agencies. The results showed that, when parents felt sorry for their children who were going to receive shots, they delayed the vaccination. Most of the children did not take the measles vaccination on the exactly recommended date, but delayed or anticipated the shots.

CONCLUSION

It is clear that there is no compliance with the government's recommended measles vaccination schedule (i.e. first dose at nine and second at 15 months of age, as recommended in 1999 and 2000). Feeling sorry for the children receiving shots can delay vaccination taking.

Seroprevalence of human parvovirus B19 in a suburban population in São Paulo, Brazil

OBJECTIVE

To analyze the prevalence of IgG antibodies to human parvovirus B19.

METHODS

Cross-sectional study in a suburban community in São Paulo, Southeastern Brazil, between November 1990 and January 1991. Randomly selected (N=435) representative samples of sera were collected from healthy children older than 15 days old and adults up to 40 years old. IgG antibodies were detected using ELISA.

RESULTS

High prevalence of IgG antibodies to B19 parvovirus was found in 87% of newborns. The prevalence of maternally derived IgG antibodies exponentially plunged up to the 19th month of age. Low prevalence of antibodies was found in the first 4 years of life, increasing up to 72% in those aged 31-40 years. It was estimated that the average age of first infection in this population is 21 +/- 7 years old and the optimal age for vaccination with a hypothetical vaccine would be 1 year of age.

CONCLUSIONS

Parvovirus B19 IgG antibody prevalence was high in newborns and those aged 31-40 years. The analysis by age groups showed a pattern similar to that found in previous studies, i.e., low prevalence of infection in children that increases with age.

HPV type infection in different anogenital sites among HIV-positive Brazilian women

OBJECTIVES

To evaluate the prevalence of human papillomavirus (HPV) types, and risk factors for HPV positivity across cervix, vagina and anus, we conducted a study among 138 women with human immunodeficiency virus (HIV).

GOAL

Compare the prevalence of different HPV types and the risk factors for HPV positivity in three sites.

RESULTS

The most frequently detected HPV types in all sites were, in decreasing order, HPV16, 53, 18, 61 and 81. Agreement between the cervix and vagina was good (kappa 0.60 - 0.80) for HPV16 and 53 and excellent (Kappa > 0.80) for HPV18 and 61. HPV positivity was inversely associated with age for all combinations including the anal site.

CONCLUSION

In HIV positive women, HPV18 is the most spread HPV type found in combinations of anal and genital sites. The relationship of anal to genital infection has implications for the development of anal malignancies. Thus, the efficacy of the current HPV vaccine may be considered not only for the cervix, but also for prevention of HPV18 anal infection among immunossuppressed individuals.