Presence Of Vertical Transmission Research Articles

Stability Analysis of HIV/AIDS Epidemic Model in the Presence of Vertical Transmission and Treatment

HIV/AIDS is a serious health problem that continues to present a significant health concern in underdeveloped nations and may be mostly brought on via unprotected sex. This study is designed and analyzed using a dynamic modeling approach to investigate the dynamic of HIV/AIDS model with vertical transmission and the impact of knowledge on its treatment. Our proposed model exhibit disease free and the endemic equilibrium. The uniqueness and the exactness of the model were investigated and the basic reproduction number using next generation matrix was obtained, Stability analysis was also carried out. The model analysis shows that the disease free equilibrium is locally asymptomatically stable (LAS) when Ro < 1. Our research suggests that treatment and awareness campaigns, when combined with other crucial control measures, may help keep the HIV/AIDS virus from spreading.

Transmission dynamics of zika virus in presence of vertical transmission and some preventive measures

Zika virus (ZIKV) infection is a vector-born human disease which enhances the chance of various types of neurological complications in affected individual. In this work we have studied a mathematical model of ZIKV by incorporating vector, direct (sexual) and vertical transmission paths of the virus. In our model also we have considered different kind of preventive measures like as: protection of susceptible individuals from mosquito bites, isolation of infected individuals from mosquito, protection of susceptible individuals from sexual interaction with infected individuals, and mosquitoes control effort. We have found the analytical expression of basic reproduction number and studied the stability of the disease free equilibrium point. Existence of endemic equilibrium point and its stability are also studied. The proposed model exhibits a backward bifurcation when the virus transmission probability from infected human to mosquito crosses the crucial value. We have fitted the model to real data and estimated the key model parameters and their 95% confidence interval which depict the ZIKV outbreak in French Polynesia in 2013-14. We also have estimated the basic reproduction number using first nine epidemic weeks (EW) data and the estimated value is 2.87 with lower and upper values are 2.47 and 3.32 respectively. The effective reproduction number of the outbreak also has been studied and which decreases gradually from 5.404 to 0.2499 during the period 11th October, 2013 and 28th March, 2014. According to our sensitivity analysis, the basic reproduction number is the most sensitive with controllable parameters, biting rate, mosquito recruitment rate, mosquito death rate and recovery rate from infection. Finally, numerically we have studied the impact of different parameters on the basic reproduction number and on the number of infected human population.

Transmission dynamics of zika virus in presence of vertical transmission and some preventive measures

Transmission dynamics of zika virus in presence of vertical transmission and some preventive measures

Impact of venereal transmission on the dynamics of vertically transmitted viral diseases among mosquitoes

Despite centuries of enormous control efforts, mosquito-borne diseases continue to show upward trend of morbidity. According to WHO reports, malaria caused 438000 deaths in the year 2015 and dengue cases have been increased 30-fold over the last five decades. To control these diseases, it is necessary to understand the transmission dynamics of them among mosquitoes. There are some vertically transmitted mosquito-borne diseases which can also be spread among mosquitoes through sexual contact (e.g., dengue, zika, chikungunya). Recent experimental observations indicate that for virus persistence in mosquito population, the role of venereal transmission cannot be ignored. It is therefore important to investigate which transmission route is more responsible for the persistence of the virus when there is no host. To this aim, we propose and analyze a novel compartmental model considering mosquito population only. To the best of authors knowledge, this is the first attempt to take into account both vertical and sexual transmission of the virus in a mathematical model. Expression representing the basic reproduction number is derived using Jacobian approach. Local stability conditions for disease-free equilibrium and complete infection equilibrium are obtained. Global sensitivity analysis of the system is performed with respect to an epidemiologically important response. While investigating the impact of sexual transmission in presence of vertical transmission, we observed that sexual transmission route has the potential to drive the equilibrium from disease free to endemic states. Further numerical experiments reveal that the virus will have higher half life in fertilized infected female mosquitoes for vertical transmission only than for venereal transmission alone. Furthermore, when both transmission pathways are active, a variety of parameters indicate threshold like behavior of the infection.

A stage structured model for HIV/AIDS in the presence of vertical transmission: The case of Ghana

Vertical transmission remains a global challenge to HIV infection dynamics. It refers to the transmission of HIV from the mother-to-child during pregnancy, delivery, and breastfeeding soon after birth. In this paper, we formulate a mathematical model to determine the transmission dynamics of HIV/AIDS and the general impact of vertical transmission on HIV/AIDS in Ghana given that horizontal transmission is the only well-documented mode of transmission. The model incorporates the treatment of juveniles, adults and both vertical and horizontal transmission of HIV/AIDS. The infection-free state and the persistent state are examined. The model is analyzed via the basic reproduction number R0. We prove that the infection-free state is globally stable when the reproduction number is less than one. The model is fitted to data obtained on HIV/AIDS from the Ghana Health Service to estimate the current and future prevalence of HIV/AIDS epidemics. We conclude that without treatment, pregnant women have a high risk of transmitting HIV to their babies. However, with treatment, even if the reproduction number of vertical transmission Rv increases, the disease can still be kept under control and fewer babies will be born with the disease. Numerical analysis, as well as sensitivity analysis, are carried out. Results from the sensitivity analysis show that the parameters that most influence the model output were, effective transmission rate β and treatment rate τ2. We noticed that increasing β increases R0 and increasing τ2 decreases R0.

Vertical Transmission in a Two-Strain Model of Dengue Fever

The role of vertical transmission in vectors has rarely been addressed in the study of dengue dynamics and control, in part because it was not considered a critical population-level factor. In this paper, we apply the pioneering modeling ideas of Ross and MacDonald, motivated by the context of the 2000-2001 dengue outbreak in Peru, to assess the dynamics of multi-strain competition. An invading strain of dengue virus (DENV-2) from Asia rapidly circulated into Peru eventually displacing DENV-2 American. A host-dengue model that considers the competing dynamics of these two DENV-2 genotypes, the resident or the American type and the invasive more virulent Asian strain, is introduced and analyzed. The model incorporates vertical transmission by DENV-2 Asian a potentially advantageous trait. Conditions for competitive exclusion of dengue strains are established. The model is used to show that lower transmission rates of DENV-2 Asian are sufficient for displacing DENV-2 American in the presence of vertical transmission.

Modelling vertical transmission in vector-borne diseases with applications to Rift Valley fever

We present two ordinary differential equation models for Rift Valley fever (RVF) transmission in cattle and mosquitoes. We extend existing models for vector-borne diseases to include an asymptomatic host class and vertical transmission in vectors. We define the basic reproductive number, 0, and analyse the existence and stability of equilibrium points. We compute sensitivity indices of 0 and a reactivity index (that measures epidemicity) to parameters for baseline wet and dry season values. 0 is most sensitive to the mosquito biting and death rates. The reactivity index is most sensitive to the mosquito biting rate and the infectivity of hosts to vectors. Numerical simulations show that even with low equilibrium prevalence, increases in mosquito densities through higher rainfall, in the presence of vertical transmission, can result in large epidemics. This suggests that vertical transmission is an important factor in the size and persistence of RVF epidemics.

The Effects of Vertical Transmission on the Spread of HIV/AIDS in the Presence of Treatment

In this study, we develop a model that incorporates treatment of both juveniles who were infected with HIV/AIDS through vertical transmission and HIV/AIDS-infected adults. We derive conditions under which the burden of HIV/AIDS can be reduced in the population both in the absence of and in the presence of vertical transmission. We have determined the critical threshold parameter (R(*)(v)), which represents the demographic replacement of infectives through vertical transmission, below which treated infected juveniles can reach adulthood without causing an epidemic. Five countries in sub-Saharan Africa are used to illustrate our results. We have concluded that R(*)(v) is dependent on the current prevalence rate but that a significant proportion of infected juveniles receiving treatment can reach adulthood without causing an epidemic.