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Eduardo Massad

Publications and source records attributed to Eduardo Massad.

18 recordsLinked to original sources
PubMed2006

The 1918 influenza A epidemic in the city of São Paulo, Brazil.

The 1918 pandemic H1N1 outbreak in the city of São Paulo is revisited. The outbreak lasted for 10 weeks and reached 116,771 officially recorded cases amongst 523,194 inhabitants. The total number of deaths summed up to 5331, with a lethality rate of 4.5% and an overall mortality rate of around 1%. We propose a mathematical model that tallies available data with good accuracy and allows the estimation of the basic reproductive number, R(0). The model showed a remarkably good accuracy in retrieving the real data from São Paulo city outbreak considering the total number of recorded cases and deaths and the timing of the outbreak. The basic reproduction number calculated of 2.68 can be compared to estimates carried out for other flu strains, like the estimates for H3N2, whose values ranged from 1.5 to 2.5. We hypothesize that the Southern parts of the world in which there was relatively little impact of the Great War, like South America, suffered a much lower H1N1 influenza mortality as compared with that reported for the Northern hemisphere heavily affected by the I World War.

Brazil↗
PubMed2006

Mental retadation: a MRI study of 146 Brazilian children.

We report results of a magnetic ressonance imaging (MRI) study of 146 Brazilian children, whose intelligence quotient scored less than 70. 50% of MRI examinations did not exhibit any signal of structural lesion (N group), whereas a focal thinning at the junction of the body and splenium of the corpus callosum; ventricular asymmetry; periventricular leukomalacia; gliosis and arachnoid cysts were among the most frequent findings in the remaining of subjects (L group). Maternal stress and altered blood pressure were the most frequent findings in the pre-natal history of both N and L children. Familial antecedents of mental deficiency were reported in 30% of both groups, whereas familiar history of alcoholism was important in N group (60% in N versus 0% in L groups). Neuropsychomotor development was delayed in 80% of the children in both groups. Aggressiveness is the most frequent finding in the post-natal children history.

Adolescent↗
PubMed2005

Yellow fever vaccination: how much is enough?

In recent years, a growing number of serious adverse events (including deaths) associated with the yellow fever (YF) vaccine has been reported. If YF vaccination were incorporated in routine programs, administered to children, the risk of deaths from this vaccine would be minimized provided that mortality of children vaccinated below 1 year were negligible. However, in affected areas the vaccine is administered to all age groups. This poses a dilemma to public health authorities - what proportion of a population subject to low risk of YF outbreaks should be vaccinated in order to minimize the total number of serious adverse events (including deaths) due both to natural infection and vaccination? In other words, how much vaccination is safe? Our results suggest that, depending on the age-specific rates of developing vaccine-induced serious adverse events and the risk of yellow fever outbreaks, the optimum proportion to vaccinate may be lower than the proportion that would prevent an epidemics or even be zero. We also show that the vaccine should not be applied to individuals older than 60 years of age because the risk of serious adverse events (including deaths) is higher for that age class. Our work is instrumental to the discussion on the optimum strategy to vaccinate affected populations against yellow fever. Therefore, the aim of this work is to estimate the optimum proportion to vaccinate against YF taking into account the risks of serious adverse events associated with both the vaccine and natural infection.

Adolescent↗
PubMed2005

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.

Canada↗
PubMed2005

Indirect oral immunization of captive vampires, Desmodus rotundus.

A vaccinia-rabies glycoprotein recombinant virus (V-RG) vaccine was tested in hematophagous bats (Desmodus rotundus) kept in captivity. The vaccine was applied in a neutral vehicle (Vaseline) spread on the back of one or two vector bats, which were then reintroduced into their groups. Our hypothesis was that, as in the case of vampire bat control by vampiricide paste, the administration of V-RG vaccine through paste to one bat could indirectly protect other bats from the same group. Eight groups were tested. The rabies virus strain used to challenge the bats was isolated from a naturally infected hematophagous bat (Desmodus rotundus). The survival proportion after the virus challenge ranged between 42.8 and 71.4%. The results are encouraging because a significant number of bats that did not receive the vaccine survived the challenge. The vaccine was shown to be safe and immunogenic to hematophagous bats. No adverse effects to vaccinia virus were observed.

Administration, Oral↗
PubMed2005

Training health informatics professionals in Brazil: rationale for the development of a new certificate program.

Current graduate degree programs in Brazil cannot fulfill the demand for highly trained health informatics practitioners. We have developed an intensive six-month program to train 20 students per year. They will receive partial subsidy from our bilateral training program and receive the title of Specialist in Health Informatics. They will benefit from a curriculum involving coursework and collaborative research designed by Brazilian and US-based faculty.

Brazil↗
PubMed2004

A Reed-Frost model taking into account uncertainties in the diagnostic of the infection.

In this paper, we model the epidemic course of a pathogen infection within a semi-closed group which generates clinical signals which do not necessarily permit its ready and certain identification. Typical examples of such a pathogen are influenza-type viruses. We allow for time-varying infectivity levels among individuals, and model the probability of infection per contact as a function of the clinical signals. In order to accomplish this, we introduce a modified chain-binomial Reed-Frost model. We obtain an expression for the basic reproduction ratio and determine conditions which guarantee that the epidemic does not survive in the long-term. These conditions being functions of the signal's distribution, they can be used to design and evaluate interventions, such as treatment protocols.

Disease Outbreaks↗
PubMed2004

Perception of disability in a public health perspective: a model based on fuzzy logic.

Measures of functional levels, commonly used to assess the safety and quality of life of individuals and populations, have not yet been derived from a fuzzy framework. The aim of this study is to estimate the degree of disability associated with varying functional levels, through a model based on fuzzy sets theory. A fuzzy linguistic model was developed to measure varying levels of functional disability, in accordance with the definitions of an individual's social and physical activities and mobility. One year of an adult's life whose mobility, social and physical activities were somewhat limited, was judged to be equivalent to 0.575 years free of functional disability. Results obtained from the fuzzy model approach those obtained with the quality of well-being scale (QWB), used as a conceptual framework. Such findings are encouraging, since the QWB is considered a consistent and valid approach for disability assessment and quality-of-life evaluation.

Adolescent↗
PubMed2003

Seroprevalence of rubella antibodies in the State of São Paulo, Brazil, 8 years after the introduction of vaccine.

Rubella vaccine was introduced in the official immunization calendar of the State of São Paulo, in 1992, at 15 months of age, following a mass vaccination targeting all children between 1 and 10 years of age. This mixed strategy was designed taking into account serological data and mathematical models to estimate the optimal ages for vaccination. To evaluate the efficacy of routine vaccination on rubella infection in São José do Rio Preto, State of São Paulo, 8 years after the introduction of vaccine, a seroprevalence survey was carried out in December 2000, comprising 1,536 subjects aging from 6 months to 25 years. Rubella specific IgG was detected in blood samples by enzyme-linked immunosorbent assay (ELISA). From 18 months to 5 years of age (covered by a mass vaccination campaign 6 months before the study) the seroprevalence was above 90%. From 6 to 8 years of age (vaccinated by routine schedule at 15 months), the seroprevalence was 76%. From 9 to 18 years of age (vaccinated at the mass campaign that introduced the vaccine 8 years before) the seroprevalence was about 85%. After 20 years of age, protection was acquired by previous infection, as they were not covered by any vaccine program. From 20 to 25 years of age, the seroprevalence was 70%. As the seroprevalence remains low at ages not vaccinated, it should be expected low infection rates at this age window. Despite this, the present situation deserves care, as routine vaccination is given a protection below the minimum level necessary (80%). The efficacy of the proposed strategy depends on better routine vaccination coverage. A second dose of vaccine should also be considered.

Adolescent↗
PubMed2003

Dengue and the risk of urban yellow fever reintroduction in São Paulo State, Brazil.

OBJECTIVE: To propose a mathematical method for the estimation of the Basic Reproduction Number, R0, of urban yellow fever in a dengue-infested area. METHODS: The method is based on the assumption that, as the same vector (Aedes aegypti) causes both infections, all the quantities related to the mosquito, estimated from the initial phase of dengue epidemic, could be applied to yellow fever dynamics. It is demonstrated that R0 for yellow fever is, on average, 43% lower than that for dengue. This difference is due to the longer dengue viremia and its shorter extrinsic incubation period. RESULTS: In this study the analysis was expanded to the epidemiological situation of dengue in S o Paulo in the year 2001. The total number of dengue cases increased from 3,582 in 2000 to 51,348 in 2001. It was then calculated R0 for yellow fever for every city which have shown R0 of dengue greater than 1. It was also estimated the total number of unprotected people living in highly risky areas for urban yellow fever. CONCLUSIONS: Currently there is a great number of non-vaccinated people living in Aedes aegypti infested area in the state of São Paulo.

Aedes↗
PubMed2003

Fuzzy epidemics.

The purpose of this paper is to provide a review of the current state of fuzzy logic theory in epidemiology, which is a recent area of research. We present four applications of fuzzy logic theory in epidemic problems, using linguistic fuzzy models, possibility measure, probability of fuzzy events and fuzzy decision making techniques. The results demonstrate that the applications of fuzzy sets in epidemiology is a very promising area of research. The final discussion sets the future stage of fuzzy sets application in epidemiology.

Acquired Immunodeficiency Syndrome↗
PubMed2003

Anogenital warts contributing to the risk of squamous intraepithelial lesions among HIV-positive women of São Paulo, Brazil.

Unsafe sexual practices may expose HIV-positive women to high-grade squamous intraepithelial lesions (SIL) and to infection with oncogenic human papillomavirus (HPV) types. A cross sectional study of 141 HIV-positive women was designed to evaluate risk factors for the development of cervico-vaginal SIL and HPV-DNA detection/typing. Uni- and multivariate forward stepwise analysis was used to determine the relationship between risk variables and HPV infection and between risk behaviour, HPV and HIV infection with development of SIL. Univariate analysis showed that HPV-DNA infection was related to previous and recurrent anogenital warts, male genital warts and cytological alteration. For final multivariate analysis, both HPV type (undetermined- and high-risk, OR=29.3 and 112.0, respectively) were statistically associated (P=0.019) with high-grade cervico-vaginal SIL. The presence of anogenital warts as well as high- and undetermined-risk HPV infection may alert to cyto/histopathological alterations. These results point out the importance of the use of barrier methods and routine early genitoscopy/treatment for HIV-infected partners.

Adult↗
PubMed2003

Uncertainties regarding dengue modeling in Rio de Janeiro, Brazil.

Dengue fever is currently the most important arthropod-borne viral disease in Brazil. Mathematical modeling of disease dynamics is a very useful tool for the evaluation of control measures. To be used in decision-making, however, a mathematical model must be carefully parameterized and validated with epidemiological and entomological data. In this work, we developed a simple dengue model to answer three questions: (i) which parameters are worth pursuing in the field in order to develop a dengue transmission model for Brazilian cities; (ii) how vector density spatial heterogeneity influences control efforts; (iii) with a degree of uncertainty, what is the invasion potential of dengue virus type 4 (DEN-4) in Rio de Janeiro city. Our model consists of an expression for the basic reproductive number (R0) that incorporates vector density spatial heterogeneity. To deal with the uncertainty regarding parameter values, we parameterized the model using a priori probability density functions covering a range of plausible values for each parameter. Using the Latin Hypercube Sampling procedure, values for the parameters were generated. We conclude that, even in the presence of vector spatial heterogeneity, the two most important entomological parameters to be estimated in the field are the mortality rate and the extrinsic incubation period. The spatial heterogeneity of the vector population increases the risk of epidemics and makes the control strategies more complex. At last, we conclude that Rio de Janeiro is at risk of a DEN-4 invasion. Finally, we stress the point that epidemiologists, mathematicians, and entomologists need to interact more to find better approaches to the measuring and interpretation of the transmission dynamics of arthropod-borne diseases.

Aedes↗
PubMed2002

Threshold conditions for infection persistence in complex host-vectors interactions.

As classically defined by Macdonald in the early 1950s, for the case of diseases with one vector and one host, the Basic Reproduction Number, R0, is defined as the number of secondary infections caused by a single infective of the same type (vector or host) during its infectiousness period in an entirely susceptible population. In the case of a disease which has one vector and one host, it is easy to show that R0 coincides with the threshold for the establishment of an endemic state: if R0 > 1 (< 1), the disease can invade (cannot invade) the host population. In this paper we examine various epidemic situations in which there are more than one vector and/or host. We show that in those more complex systems it is not possible to deduce a single R0 but rather a threshold for infection persistence which is a composite of several quantities closely related to the classical expression of R0. Another definition of R0 given by Diekmann, Heesterbeek and Metz, and denoted in this paper R0NGO is discussed and applied as an alternative to calculate the thresholds for infection establishment.

Animals↗
PubMed2002

Training in health informatics in Brazil.

Developing countries, such as Brazil, are increasingly suffering from a severe shortage of health informatics specialists. Training of professionals in this field is expensive, and there is a limited supply of high-quality teaching resources available. We report on five initiatives of the Brazil/USA training program in health informatics. The main goal of this program is to train professionals in establishing medical informatics programs in Brazilian universities and major healthcare facilities.

Brazil↗
PubMedDate not supplied

The intensity of transmission of hepatitis A and heterogeneities in socio-environmental risk factors in Rio de Janeiro, Brazil.

The objective of this work was to assess the intensity of transmission of hepatitis A in Rio de Janeiro, Brazil. We also used the estimation of the parameters of a deterministic model to study the effects of risk factors. Age-specific seroprevalence of antibodies against hepatitis A virus (HAV) was obtained from a survey screening in a city of the metropolitan area of Rio de Janeiro, in 1997. From the seroprevalence data, we estimated the age-dependent force of infection (lambda) and the average age of first infection (A), using a deterministic model. To evaluate the influence of the environmental risk factors, we estimated the same parameters stratifying the sample for the selected socio-environmental risk factors: the number of years of schooling of the female responsible for the house, crowding within the bedroom, number of water taps and fittings, and the presence of sewage in front of the house. For the whole sample, the maximum force of infection estimated was 0.12/year and the average age of infection was 10.1 years. This last parameter decreased as the number of persons per bedroom increased, and also when the number of water taps and the number of years of schooling of the woman responsible for the house decreased. The proposed environmental interventions may lead to a decrease in the intensity of transmission of HAV and an increase in the average age of first infection in the next few years. This may have public health implications, since hepatitis A is more severe in adults. In this context, specific vaccination programmes may be necessary, as in developed countries.

Adolescent↗
PubMedDate not supplied

Risk factors associated with genital warts in HIV-positive Brazilian women.

AIMS AND BACKGROUND: In Brazil, the female population has been increasingly infected with human immunodeficiency virus (HIV), and uterine cervix carcinoma now represents the second highest cause of mortality. Although HIV infection among women is associated with an increased prevalence of cervical cancer precursors, the co-infection with human papillomavirus (HPV) is considered to be a necessary but not sufficient factor to induce genital lesions. This study was conducted to identify risk factors associated with the history of genital warts among HIV-positive women. METHODS: A comparative cross-sectional evaluation was applied to 141 HIV-positive women. All patients were submitted to colposcopy, smear cytology, directed biopsy, and HPV-DNA detection. The chi-square, Fisher's exact test, and the odds ratio (OR, 95%; confidence interval, CI) were used to evaluate associations between history of genital warts and risk factors. RESULTS: A history of genital warts presented associations with: a) age at first sexual intercourse < or = 17 years (OR, 0.42; CI, 0.16-1.11); b) history of genital warts in sex partners (OR, 11.39; CI, 4.21-30.76), especially with recurrent episodes (OR, 6.60; CI, 2.69-16.12); c) drug addiction (OR, 2.38; CI, 1.09-5.19), especially in crack users (OR, 5.34; CI, 1.64-17.41); d) cervical HPV infection (OR, 2.75; CI 1.09-6.90); e) cervical infection caused by only one HPV type (OR, 2.77; CI 1.06-7.20); f) perianal HPV infection (OR, 2.30; CI, 0.70-7.56), associated with negative results for undetermined risk HPV (OR, 8.41; P = 0.04); and g) no antiretroviral therapy (OR, 3.41; P = 0.07). CONCLUSIONS: Evaluation of behavioral risk factors associated with a genital wart history is an important tool to prevent and reduce persistent HPV infection, and consequently genital cancer precursors in HIV infected women.

Adult↗