Infected Immigrants Research Articles

The effect of immigration of infectives on disease-free equilibria.

Many disease transmission models exhibit a threshold behaviour based on the basic reproduction number [Formula: see text], where the disease-free equilibrium is locally asymptotically stable if [Formula: see text] and unstable if [Formula: see text]. However, if a system includes immigration of infected individuals, then there is no disease-free equilibrium. We consider how the disease-free equilibrium moves as the level of immigration of infected individuals is increased from 0, finding, under mild assumptions, that the disease-free equilibrium becomes an endemic equilibrium if [Formula: see text] and leaves the biologically relevant space (by having at least one coordinate become negative) if [Formula: see text].

Diagnosis of Latent Mycobacterium tuberculosis Infection in the Era of Interferon Gamma Release Assays

Mycobacterium tuberculosis (MTB), an acid-fast bacterium, is a leading cause of respiratory illness and death worldwide. Individuals can be latently infected and can harbor the organism without clinical evidence of disease for years. Screening and treatment of numerous populations, including health care workers, recent contacts of actively infected individuals, immunocompromised individuals, children, and immigrants from countries where MTB is endemic, is essential to eradicate the infection by 2050, as the World Health Organization envisions. Detection of active and latent infection historically has utilized tuberculin skin tests and other clinical findings. Interferon gamma release assays can test whether a patient has had MTB exposure with improved sensitivity and specificity over tuberculin skin testing. This article reviews the history of MTB testing, compares available interferon gamma release assays, and discusses the new developments related to latent-MTB infection testing.

Chagas Disease Recommendations for Solid-Organ Transplant Recipients and Donors.

Chagas Disease Recommendations for Solid-Organ Transplant Recipients and Donors.

Screening and evaluation of lymphatic filariasis in immigrants from endemic countries residing in a focus where it is considered eliminated in the Southern Region of Brazil: A risk of reemergence?

Lymphatic filariasis (LF) has been targeted by the World Health Organization for elimination by the year 2020. However, migration of infected individuals from areas where LF is endemic to areas considered non-endemic or foci for the control and elimination may jeopardize the achievement of this goal. The aim of the present study was to evaluate the occurrence of filarial infection by way of circulating filarial antigen (CFA) circulation using the point of care AD12-immunochromatography card (POC-ICT) among immigrants from Haiti residing in Chapecó, Santa Catarina, between May and October 2015. Of the 420 subjects examined, 77.4% were male, aged 19–54 years. Ten (2.38%) were POC-ICT positive. Of this total, one was not found. Two individuals were negative for Og4C3-ELISA and DNA/Wb-PCR in all biological samples, but positive for the anti-filarial antibody Bm14 and only one showed microfilaremia (1mf/mL). These findings point to the importance of the Brazilian surveillance action to reduce the possibility of reintroduction of LF in Chapecó, Santa Catarina, by infected immigrants, and to guarantee the success of the National LF Elimination Plan.

A high rate of HIV‐1 acquisition post immigration among migrants in Sweden determined by a CD4 T‐cell decline trajectory model

There is a lack of knowledge about the extent to which migrants become HIV-1 infected after arrival in European countries. The objective of this study was to assess the extent to which migrants to Sweden become HIV-1 infected post immigration using a CD4 T-cell decline trajectory model. All migrants (n = 2268) who were ≥ 15 years old, were diagnosed with HIV-1 infection in the period 1983-2013, had a known year of arrival in Sweden, did not have primary HIV infection and were not infected via mother-to-child transmission were included in the study. The CD4 T-cell decline trajectory model was applied and estimates of HIV acquisition were compared to the clinical reports. Phylogenetic analysis was performed in a subset of patients to explore whether this would favour the model or the doctor's estimate. The model estimated 19% of individuals to have been infected after arrival in Sweden, whereas the physician's estimate was 12%. In 79% of cases the estimates agreed. Discordance was predominantly seen when the doctor estimated HIV acquisition to have occurred before arrival in Sweden, while the model estimated it to have occurred after arrival in Sweden, and this type of discordance was seen in 10% of all patients. The probability of a discordance was greater for older patients, those with a high first CD4 T-cell count and those infected via heterosexual transmission. The phylogenetic analysis showed a higher concordance with the CD4 model than with the clinical reports (36 vs. 13%, respectively). The model indicated that a substantially higher proportion of migrants are infected after arrival in Sweden than estimated using clinical routine reports. It is therefore important to further emphasize primary preventive measures among migrants who have established themselves in their new country.

HEPATITIS C VIRUS, HEPATITIS B VIRUS AND HUMAN IMMUNODEFICIENCY VIRUS INFECTION IN ILLEGAL IMMIGRANT’S POPULATION ATTENDED TO AL- JABAL ALAKHTER AREA- LIBYA

Assess the prevalence of Human Immunodeficiency Virus (HIV), Hepatitis B and C Virus and serological markers in immigrant people of various nationalities, living in the AL- Jabal alakhdar area. HIV, Hepatitis B and C are, and will remain for some time, major health problems in Libya.The retrospective study was conducted in AL- Bayda, Cyrene and AL-Quba illegal immigrant centers between OctoberDecember 2017.All samples were tested using enzyme immunoassay (ELISA). The study considers a total of 14,918 samples, mostly males. The highest prevalence rate of viral infection was HBsAg with 35 (1.22%) recorded in Al-Bayda center in 2016, while the lowest was 9 (1.82%) recorded in Al-Qubba center in 2015. The highest value of HCV was 18 (0.81%) in Al-Bayda center in 2016, while the highest value is in Both Elqubba (1.12%) and Cyrene centers (0.30%) which were recorded in 2017. HIV infected person in 2015,was one male (0.2%) in the Elqubba center and his nationality was Egyptian and only two females were recorded (0.4%) in Cyrene in 2016, their nationality waschad, while in 2017 One female was recorded (0.06%) in Cyrene and her nationality was chad and one male (0.2%) in Al-bayda from Egypt. Number of males (12919) exceeds females (1999). The highest frequency was 15 males and their ages were 24 years old. The highest level of infected illegal immigrants was from Egypt as 429 of them infected followed by 134 Chadians , 118 Sudanese, 105 Bangladesi’s, 26 Syrians, 6 turkish and 6 Palestinian , 5 Tunisians and 3 Nigerians respectively.

Impulsive Vaccination for an Epidemiology Model

This paper investigates sufficient conditions of almost periodic sand periodic solutions of an integral model under impulsive controls. Since the model is of generic epidemiological interest, such impulsive controls are either vaccination actions or abrupt variations of the infected population due to infected immigration or lost of infective numbers due to either vaccination or lost of infected population by out-migration.

Stability Analysis of a Human-Mosquito Model of Malaria with Infective Immigrants

Stability Analysis of a Human-Mosquito Model of Malaria with Infective Immigrants

The Impact of Infective Immigrants on the Spread and Dynamics of Zika Viruss

In this paper, a compartment model has been built, presented and investigated the dynamics and spread of zika virus in both human and mosquito populations. It is focused to study the impact of symptomatic and asymptomatic infective immigrants on the spread of zika virus. A new mathematical model SI1I2R for human and SI model for vector population has been designed and presented. Here I1 is symptomatic infective and I2 is asymptomatic infective human populations. The present model is developed making some reasonable modifications in the corresponding epidemic SIR model by considering symptomatic and asymptomatic infective immigrants. Susceptible vectors get infection either from symptomatic or asymptomatic infected human populations. The basic reproduction number is derived using the next generation matrix method. Disease free equilibrium point is found and endemic equilibrium state is identified. It is shown that the disease free equilibrium point is locally and globally asymptotically stable if the reproduction number takes a value less than one unit and unstable if it is more than one unit. Simulation study is conducted using MATLAB ode45.

Control Strategies for TB Epidemics

A model for tuberculosis (TB) that includes immigration of susceptible and infected individuals is presented and analyzed. Infected individuals are structured by time since infection to include a long and variable latency period, and individuals with active TB have an increased mortality rate. Two control problems are formulated and analyzed, minimizing the impact of infection by controlling infected immigrants and/or screening for detection and treatment of infected individuals before they develop active TB.

The Impact of Infective Immigrants on the Spread of Dog Rabies

In this paper, it is proposed and analyzed a new mathematical model and that is developed on the basis of some reasonable modification made to the standard epidemic model. The impact of immigration, treatment and the effect of vaccination are included in the model. The basic reproduction number is derived using the next generation matrix method. Disease free equilibrium point is found and endemic equilibrium state is identified. Numerical simulation study is conducted using <i>ode 45</i> of MATLAB. It has been shown that the solution is positive and bounded. Algebraic expression for the reproduction number is constructed. Equilibrium points are identified and their stability analysis is carried out. It is pointed out that the disease dies out if the immigration of the infected dogs is controlled and the vaccination and the treatments are improved. Otherwise, the disease spreads rapidly in the dog population and it becomes an epidemic. Further, it is also pointed out that the impact of infective immigrants on the spread of dog rabies is positive and additive. The details are presented and discussed in the text.

Prevalence of Trypanosoma cruzi infection among Bolivian immigrants in the city of São Paulo, Brazil

With the urbanisation of the population in developing countries and the process of globalisation, Chagas has become an emerging disease in the urban areas of endemic and non-endemic countries. In 2006, it was estimated that the prevalence of Chagas disease among the general Bolivian population was 6.8%. The aim of the present study was to determine the prevalence of Trypanosoma cruzi infection among Bolivian immigrants living in São Paulo, Brazil. This study had a sample of 633 volunteers who were randomly selected from the clientele of primary care units located in the central districts of São Paulo, Brazil. Infection was detected by two different ELISA assays with epimastigote antigens, followed by an immunoblot with trypomastigote antigens as a confirmatory test. The prevalence of the infection was 4.4%. Risk factors independently associated with the infection were: a history of rural jobs in Bolivia, knowledge of the vector involved in transmission, and having relatives with Chagas disease. Brazil has successfully eliminated household vector transmission of T. cruzi, as well as its transmission by blood transfusion. The arrival of infected immigrants represents an additional challenge to primary care clinics to manage chronic Chagas disease, its vertical transmission, and the blood derivatives and organ transplant programs.

Oesophageal motility disorders in infected immigrants with Chagas disease in a non-endemic European area.

Immigration-related new diseases pose a growing challenge for healthcare services in receptor countries. Following Latin American migration, Chagas disease has inevitably appeared in Europe. To determine the prevalence and characteristics of oesophageal motility disorders in immigrants infected with Trypanosoma cruzi, using high resolution oesophageal manometry (HREM). In all newly-diagnosed cases with chronic Chagas infection referring upper digestive symptoms, a protocolized clinical evaluation and complementary tests including barium oesophagogram and HREM were carried out. As control group, 14 healthy subjects from the same endemic areas were studied with HREM. We included 61 patients (46 female, 15 male; age range 26-63 years). Only seven patients (11%) had a minor alteration on barium oesophagogram. By contrast, 23 (37%) patients showed an alteration in oesophageal manometry, mainly minor motility disorders (34%). Only one healthy control (7%) had a minor motility disorder at HREM (p = 0.029 vs. patients). Oesophageal motor disorders in infected immigrants with Chagas disease are common, and mainly characterized by a minor motility disorder that is not detected by barium oesophagogram. Hence, as well as barium oesophagogram examination, HREM should be considered, to assess oesophageal damage in this specific group of patients.

On the time to reach a critical number of infections in epidemic models with infective and susceptible immigrants

In this paper we examine the time T to reach a critical number K0 of infections during an outbreak in an epidemic model with infective and susceptible immigrants. The underlying process X, which was first introduced by Ridler-Rowe (1967), is related to recurrent diseases and it appears to be analytically intractable. We present an approximating model inspired from the use of extreme values, and we derive formulae for the Laplace–Stieltjes transform of T and its moments, which are evaluated by using an iterative procedure. Numerical examples are presented to illustrate the effects of the contact and removal rates on the expected values of T and the threshold K0, when the initial time instant corresponds to an invasion time. We also study the exact reproduction number Rexact,0 and the population transmission number Rp, which are random versions of the basic reproduction number R0.

Modeling the Combined Effect of Vertical Transmission and Variable Inflow of Infective Immigrants on the Dynamics of HIV/AIDS

In this paper, a Non linear Mathematical model is proposed and studied the combined effect of vertical transmission (MTCT) and variable inflow of infective immigrants on the dynamics of HIV/AIDS. Vertical transmission means propagation of the disease from mother to children. ‘Variable inflow of infective immigrants’ includes both the aware and unaware infected immigrants. The equilibrium points of the model are found and the stability analysis of the model around these equilibrium points is conducted. The stability analysis on the model shows that the disease free equilibrium point <i>E</i>₀ is locally asymptotically stable when <i>R</i>₀<1. The positive endemic equilibrium point <i>E^*</i> is shown to be locally asymptotically stable when <i>R</i>₀>1. Further it is shown that <i>R</i>₀><i>R´</i>₀, this shows that the basic reproduction number of the present model is greater than the one which is obtained from the model modeled without vertical transmission. Through vertical transmission the disease flows from infected mother to children. That is, Vertical transmission contributes positively to the spread of the disease. Numerical simulation of the model is carried out to assess the effect of unaware HIV infective immigrants and vertical transmission (MTCT) in the spread of HIV/AIDS disease. The result showed that HIV infective immigrants and vertical transmission (MTCT) significantly affects the spread of the disease. Screening of the disease reduces the spread of HIV and also prevents mother to child transmission. It is well accepted that both vertical transmission and immigration contribute positively to the spread of the disease and these two parameters cannot be avoided in practice. Hence, the purpose of this study is to investigate the combined effect of vertical transmission, unaware and aware infected immigrants on the spread of HIV/AIDS and offers possible intervention strategies.

An epidemic model on the dispersal networks at population and individual levels

A network model at the population level and the individual level, which simulates both between-herd dynamics and within-herd dynamics, is formulated. We investigated effects of dispersal rates and local dynamics on the outcome of an epidemic at the population level. Numerical studies show that dispersal may strengthen spread of the disease on average, but lead to a less tendency for damped oscillation. Further, different types of clustering behaviors, from synchronized to completely desynchronized, are observed within our system. The results show that strengthening the coupling between farms via the immigration of infectives tends to enhance (in-phase) synchronization. Dynamic complexity, including chaotic, quasi-periodic or periodic behaviour, is observed in our model with varying the coupling strength. The main results help to explain differences in observed epidemiological patterns and to identify possible causes for different strains of Salmonella developing so much variation in their infection dynamics in UK dairy herds.

On the Optimal Control of Vaccination and Treatments for an SIREpidemic Model with Infected Immigrants

This paper is proposed to study rigorously the optimal control of vaccination and treatments for an SIR(Susceptible-Infected-Recovered) Epidemic model with infected immigrants. The impact of infected immigrants is studied in order to understand and assess its influence on the transmission dynamics for an SIR(Susceptible-Infected-Recovered) Epidemic model. The main goal of this work is to find the optimal treatment and vaccination strategies in combination that will minimize the cost of vaccination and treatment as well as the number of infective and to measure the influence of the flow of infected immigrants in the transmission of disease in a population.Qualitative and quantitative analysis of the model with respect to stability of the disease free equilibrium and endemic equilibrium under the influence of the two control strategies are carried out.It is established that in the absence of infected immigrants the disease free equilibrium exist and is locally asymptotically stable. Hence, the optimal interventions for the disease control using Pontryagin’s Maximum Principle( PMP) are illustrated and various numerical simulations are performed to discuss the solution.

Mathematical Analysis of Control Strategies of HCV in a Community with Inflow of Infected Immigrants

In this paper, we derive and analyse rigorously a mathematical model of control strategies (scree- ning, education, health care and immunization) of HCV in a community with inflow of infected im- migrants. Both qualitative and quantitative analysis of the model is performed with respect to sta- bility of the disease free and endemic equilibria. The results show that the disease free equili- brium is locally stable at threshold parameter less than unity and unstable at threshold parameter greater than unity. Using Lyapunov method, endemic equilibrium is globally stable under certain conditions. Numerical simulation of the model is implemented to investigate the sensitivity of certain key parameters on the HCV model in a community with inflow of infected immigrants. However, analysis shows that screening, education, health care and immunization have the effect of reducing the transmission of the disease in the community.

Optimal control analysis of hepatitis C virus with acute and chronic stages in the presence of treatment and infected immigrants

In this paper, we consider a deterministic hepatitis C virus (HCV) model and study the impact of optimal control on the screening of immigrants and treatment of HCV on the transmission dynamics of the disease in a homogeneous population with constant immigration of susceptibles. First, we derived the condition in which disease-free equilibrium is locally asymptotically stable and established that a stable disease-free equilibrium can only be achieved in the absence of infective immigrants. Second, we investigated the impact of each control mechanism individually and the combinations of these strategies in the control of HCV. The costs associated with each of these strategies are also investigated by formulating the costs function problem as an optimal control problem, and we then use the Pontryagin's Maximum Principle to solve the optimal control problems. From the numerical simulations we found that the optimal combination of treatment of acute-infected and chronic-infected individuals control strategy produced the same results as the combination of the three strategies (combination of screening of immigrants, treatment of acute-infected and chronic-infected individuals). By our model and these results, we suggest the treatment of acute-infected and chronic-infected individuals control strategy should be optimized where resources are scarce, because the implementation of the three strategies (combination of screening of immigrants, treatment of acute-infected and chronic-infected individuals) would imply additional cost.

Chagas disease in Australia and New Zealand: risks and needs for public health interventions

International migration has changed the global distribution of Chagas disease, with the emerging importance of non-endemic regions. We aimed at better documenting the Australia and New Zealand risk of Chagas disease and needs for interventions. We reviewed Chagas disease-related evidences, policies and practices in Australia and New Zealand and calculated the estimated prevalence. Australia hosts a rapidly growing population at risk and had 1928 infected residents in 2011; New Zealand had 98 in 2006. These figures underestimate the real situation, as they do not consider non-permanent residents. The only existing policy in both countries is the identification of blood donors with a history of or a risk of infection via questionnaire. There is no programme of detection and care of patients. The lifetime economic burden of disease for society is potentially very high. Chagas disease is an emerging health risk with potential high human and economic costs in Australia and New Zealand in the absence of public health attention. Implementing strategies to screen high-risk groups and prevent transmission should be considered. Moreover, migration between the Western Pacific and Chagas endemic regions and the presence of vectors means this risk applies in the whole region.