Papers by Francisco A . B . Coutinho
Epidemiology and Infection, 2018
Vaccinating monkeys against yellow fever (YF) has been a common practice in the beginning of the ... more Vaccinating monkeys against yellow fever (YF) has been a common practice in the beginning of the 17D vaccine development. Although it may seem strange at first sight, vaccinating monkeys as a public health strategy is, we think, feasible and theoretically could eliminate the infection among non-human primates, interrupting the virus circulation (or significantly reducing it) and therefore reducing the risk of spilling over to the human population. We propose a series of studies that could demonstrate (or not) the efficacy and feasibility of vaccinating non-human primates YF reservoirs living in green areas of urban centres to cut off or curb the virus circulation that recurrently spill over to the human population. Therefore, vaccinating monkeys in relatively small green areas of the urban centres is perhaps the ultimate solution for the Brazilian recurrent YF epizootics.
Tropical Medicine & International Health, 2015
This work is an attempt to estimate the risk of infections importation and exportation by travele... more This work is an attempt to estimate the risk of infections importation and exportation by travelers. In it we propose a model that takes into account the force of infection of the disease in the endemic country, which can either be a visited country (source of infection importation) or a country from where local residents export the infection when travel in the latent condition for disease-free countries. The model is deterministic but a preliminary stochastic formulation is presented in the appendix. It considers two countries: one is the host home-country and the other is the source country (with an endemic infectious disease). Susceptible individuals travel from their home-country to the endemic country and eventually return infected. The input of the model is the force of infection at the visited/source country which is assumed to be known and we assume that, in the case of disease importation, travelers are subject to the same risk of infection as local residents but do not con...
Epidemiology and Infection, 2016
SUMMARYThe classical Ross–Macdonald model is often utilized to model vector-borne infections; how... more SUMMARYThe classical Ross–Macdonald model is often utilized to model vector-borne infections; however, this model fails on several fronts. First, using measured (or estimated) parameters, which values are accepted from the literature, the model predicts a much greater number of cases than what is usually observed. Second, the model predicts a single large outbreak that is followed by decades of much smaller outbreaks, which is not consistent with what is observed. Usually towns or cities report a number of recurrences for many years, even when environmental changes cannot explain the disappearance of the infection between the peaks. In this paper, we continue to examine the pitfalls in modelling this class of infections, and explain that, if properly used, the Ross–Macdonald model works and can be used to understand the patterns of epidemics and even, to some extent, be used to make predictions. We model several outbreaks of dengue fever and show that the variable pattern of yearly ...
Journal of Biological Systems, 1995
Two different theoretical functions are proposed for the age-dependent transmission coefficients ... more Two different theoretical functions are proposed for the age-dependent transmission coefficients which takes into account the distribuitions of the contact probabilities between susceptible individuals of age a with infected individuals of age a′. A numerical simulation is presented with measles and rubella data from two distinct communities. The impact of control measures is also simulated using the assumed functions for the age-dependent transmission coefficients.
Infectious Disease Modelling, 2021
Testing for detecting the infection by SARS-CoV-2 is the bridge between the lockdown and the open... more Testing for detecting the infection by SARS-CoV-2 is the bridge between the lockdown and the opening of society. In this paper we modelled and simulated a test-trace-andquarantine strategy to control the COVID-19 outbreak in the State of São Paulo, Brasil. The State of São Paulo failed to adopt an effective social distancing strategy, reaching at most 59% in late March and started to relax the measures in late June, dropping to 41% in 08 August. Therefore, São Paulo relies heavily on a massive testing strategy in the attempt to control the epidemic. Two alternative strategies combined with economic evaluations were simulated. One strategy included indiscriminately testing the entire population of the State, reaching more than 40 million people at a maximum cost of 2.25 billion USD, that would reduce the total number of cases by the end of 2020 by 90%. The second strategy investigated testing only symptomatic cases and their immediate contacts e this strategy reached a maximum cost of 150 million USD but also reduced the number of cases by 90%. The conclusion is that if the State of São Paulo had decided to adopt the simulated strategy on April the 1st, it would have been possible to reduce the total number of cases by 90% at a cost of 2.25 billion US dollars for the indiscriminate strategy but at a much smaller cost of 125 million US dollars for the selective testing of symptomatic cases and their contacts.
Revista Brasileira de Ensino de Física, 2021
This is the first of a series of articles dealing with the casual use of distributions made by ph... more This is the first of a series of articles dealing with the casual use of distributions made by physicists and engineers. This use is very economical but sometimes leads to embarrassing conclusions that are difficult to justify with rigorous theories of distributions.
American Journal of Physics, Mar 1, 1998
Epidemiology and Infection, 2021
In this paper, we present a method to estimate the risk of reopening of schools illustrated with ... more In this paper, we present a method to estimate the risk of reopening of schools illustrated with the case of the State of São Paulo, Brazil. The model showed that, although no death of children would result from the reopening of the schools in the three cities analysed, the risk of asymptomatic and symptomatic cases and secondary cases among teachers, school staff and relatives of the children is not negligible. Although the epidemic hit different regions with different intensities, our model shows that, for regions where the incidence profile is similar to the cities analysed, the risk of reopening of schools is still too high. This in spite of the fact that incidences in these cities were declining in the period of the time considered. Therefore, although we cannot extend the result to the entire country, the overall conclusion is valid for regions with a declining incidence and it is even more valid for regions where incidence is increasing. We assumed a very conservative level o...
Travel Medicine and Infectious Disease, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Infectious Disease Modelling, 2018
We consider nested or multiscale models to study the effect of the temporal evolution of the dise... more We consider nested or multiscale models to study the effect of the temporal evolution of the disease within the host in the population dynamics of the disease, for one and two infectious agents. We assumed a coupling between the within-host infection rate and the between-host transmission rate. The age of infection within each individual in a population affects the probability of transmission of the disease to a susceptible host and this will affect the temporal evolution of the disease in the host population. To analyze the infection within the host, we consider bacterial-like and viral-like infections. In the model for two infectious agents, we found that, when strain 2 has a basic reproduction number R 02 greater than the basic reproduction number R 01 of strain 1, strain 2 replaces strain 1 in the population. However, if R 02 > R 01 but the values are closer, the replacement does not occur immediately and both strains can coexist for a long time. We applied the model to a scenario in which patients infected with the hepatitis C virus (HCV) are cleared of HCV when super-infected with the hepatitis A virus (HAV). We compared the time for the replacement of HCV by HAV in the population considering instantaneous and noninstantaneous replacement within the individuals. The model developed can be generalized for more than two infectious agents.
Epidemiology and Infection, 2016
Journal of Physics A: Mathematical and General, 2005
By using Wu and Yu's pseudo-potential, we construct point interactions in one dimension that ... more By using Wu and Yu's pseudo-potential, we construct point interactions in one dimension that are complex but conform to space–time reflection invariance. The resulting point interactions are equivalent to those obtained by Albeverio, Fei and Kurasov as self-adjoint extensions of the kinetic energy operator.
Canadian Journal of Physics, 1988
Various features that are characteristic of the two-body Dirac equation but not of the one-body D... more Various features that are characteristic of the two-body Dirac equation but not of the one-body Dirac equation are illustrated by means of solvable examples (mainly square-well potentials) in one space dimension. For the Lorentz character of the potential there are three types; vector, scalar, and pseudoscalar. We classify the bound-state solutions as normal and abnormal. As the interaction is adiabatically switched off, the energy of the normal solutions reaches 2m (the sum of the masses of the constituent particles), whereas the energy of the abnormal solutions becomes zero. When the sharp edge of the square-well potential is smeared out, some of the solutions become unnormalizable and hence unacceptable. This leads to a certain restriction on the choice of the potential. The two-body Dirac equation with a finite-range interaction is not exactly covariant. The degree of noncovariance is examined.
Epidemiology and Infection, 2017
SummaryThe timing and origin of Zika virus (ZIKV) introduction in Brazil has been the subject of ... more SummaryThe timing and origin of Zika virus (ZIKV) introduction in Brazil has been the subject of controversy. Initially, it was assumed that the virus was introduced during the FIFA World Cup in June–July 2014. Then, it was speculated that ZIKV may have been introduced by athletes from French Polynesia (FP) who competed in a canoe race in Rio de Janeiro in August 2014. We attempted to apply mathematical models to determine the most likely time window of ZIKV introduction in Brazil. Given that the timing and origin of ZIKV introduction in Brazil may be a politically sensitive issue, its determination (or the provision of a plausible hypothesis) may help to prevent undeserved blame. We used a simple mathematical model to estimate the force of infection and the corresponding individual probability of being infected with ZIKV in FP. Taking into account the air travel volume from FP to Brazil between October 2013 and March 2014, we estimated the expected number of infected travellers arr...
PLOS ONE
In this paper we calculate the variation of the estimated vaccine efficacy (VE) due to the time-d... more In this paper we calculate the variation of the estimated vaccine efficacy (VE) due to the time-dependent force of infection resulting from the difference between the moment the Clinical Trial (CT) begins and the peak in the outbreak intensity. Using a simple mathematical model we tested the hypothesis that the time difference between the moment the CT begins and the peak in the outbreak intensity determines substantially different values for VE. We exemplify the method with the case of the VE efficacy estimation for one of the vaccines against the new coronavirus SARS-CoV-2.
OBJECTIVESWith declining numbers of COVID-19 cases in the State of São Paulo, Brazil, social dist... more OBJECTIVESWith declining numbers of COVID-19 cases in the State of São Paulo, Brazil, social distancing measures were gradually being lifted. The risk of an increase in the number of cases, however, cannot be overlooked. Even with the adoption of non-pharmaceutical interventions, such as restrictions on mass gatherings, wearing masks, and complete or partial closure of schools, other public health measures may help to control the epidemic. We aimed to evaluate the impact of the contact tracing of symptomatic individuals on the COVID-19 epidemic regardless of the use of diagnostic testing.METHODSWe developed a mathematical model that includes isolation of symptomatic individuals and tracing of contacts to assess the effects of the contact tracing of symptomatic individuals on the COVID-19 epidemic in the State of São Paulo.RESULTSFor a selection efficacy (proportion of isolated contacts who are infected) of 80%, cases and deaths may be reduced by 80% after 60 days when 5000 symptomat...
Epidemiology and Infection, 2020
We present two complementary model-based methods for calculating the risk of international spread... more We present two complementary model-based methods for calculating the risk of international spread of the novel coronavirus SARS-CoV-2 from the outbreak epicentre. One model aims to calculate the number of cases that would be exported from an endemic country to disease-free regions by travellers. The second model calculates the probability that an infected traveller will generate at least one secondary autochthonous case in the visited country. Although this paper focuses on the data from China, our methods can be adapted to calculate the risk of importation and subsequent outbreaks. We found an average R0 = 5.31 (ranging from 4.08 to 7.91) and a risk of spreading of 0.75 latent individuals per 1000 travellers. In addition, one infective traveller would be able to generate at least one secondary autochthonous case in the visited country with a probability of 23%.
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Papers by Francisco A . B . Coutinho