Open Access. Powered by Scholars. Published by Universities.®
- Institution
-
- Virginia Commonwealth University (7)
- Illinois State University (3)
- University of Nebraska - Lincoln (2)
- Dartmouth College (1)
- Hollins University (1)
-
- LSU Health Science Center (1)
- Prairie View A&M University (1)
- Stephen F. Austin State University (1)
- The University of Maine (1)
- The University of San Francisco (1)
- University at Albany, State University of New York (1)
- University of Missouri, St. Louis (1)
- University of New Mexico (1)
- University of South Florida (1)
- University of Tennessee, Knoxville (1)
- University of Wisconsin Milwaukee (1)
- Utah State University (1)
- Walden University (1)
- Wilfrid Laurier University (1)
- Keyword
-
- Epidemiology (6)
- Ecology (4)
- Climate change (2)
- Coevolution (2)
- Disease (2)
-
- Emerging infectious disease (2)
- Evolution (2)
- HIV (2)
- Ixodes scapularis (2)
- Surveillance (2)
- ALAN (1)
- ANEMIA (1)
- Acquired immunity (1)
- Adaptation (1)
- Age (1)
- Anaplasmosis (1)
- Angiostrongylus cantonensis (1)
- Animals (1)
- Antibiotic resistance (1)
- Antiretroviral (1)
- BABY'S BIRTH WEIGHT (1)
- Babesiosis (1)
- Bats (1)
- Bioassay (1)
- Biology (1)
- Blacklegged ticks (1)
- Body fat (1)
- Borrelia burgdorferi (1)
- Butanediol aphid beetle olfactometry transmission blackleg (1)
- Canada (1)
- Publication Year
- Publication
-
- Biology and Medicine Through Mathematics Conference (6)
- Annual Symposium on Biomathematics and Ecology Education and Research (3)
- Applications and Applied Mathematics: An International Journal (AAM) (1)
- Biology Department Faculty Works (1)
- Biomedical Sciences ETDs (1)
-
- Dartmouth Scholarship (1)
- Doctoral Dissertations (1)
- Electronic Theses and Dissertations (1)
- Faculty Publications (1)
- Harold W. Manter Laboratory of Parasitology: Faculty and Staff Publications (1)
- Human–Wildlife Interactions (1)
- Legacy Theses & Dissertations (2009 - 2024) (1)
- Master's Projects and Capstones (1)
- Public Health Resources (1)
- School of Medicine Faculty Publications (1)
- Theses and Dissertations (1)
- Theses and Dissertations (Comprehensive) (1)
- USF Tampa Graduate Theses and Dissertations (1)
- Undergraduate Honors Theses (1)
- Undergraduate Research Posters (1)
- Walden Dissertations and Doctoral Studies (1)
- Publication Type
Articles 1 - 28 of 28
Full-Text Articles in Epidemiology
Investigation Of Orthohantavirus Genetics In Rodent Reservoirs And Clinical Samples, Samuel M Goodfellow
Investigation Of Orthohantavirus Genetics In Rodent Reservoirs And Clinical Samples, Samuel M Goodfellow
Biomedical Sciences ETDs
Orthohantaviruses are negative-sense, single stranded RNA viruses with trisegmented genomes that can cause severe disease in humans and are carried by several host reservoirs throughout the world. In the United States, Sin Nombre orthohantavirus (SNV) is the primary cause of hantavirus cardiopulmonary syndrome (HCPS) with a fatality rate of ~36% and the highest cases occuring in the southwest region. The primary SNV host reservoir is thought to be the western deer mouse, Peromyscus maniculatus, however it has been shown that other rodents can carry different orthohantaviruses. We designed a pan-orthohantavirus detection tool to survey several small mammal populations throughout New …
Proposing An Rna Interference (Rnai)-Based Treatment For Human Immunodeficiency Virus (Hiv) By Analyzing The Post-Transcriptional Gene Targeting Of Sars-Cov-2, Hepatitis C Virus, And A549 Lung Cancer Cells, Arjun Jagdeesh
Undergraduate Research Posters
Human Immunodeficiency Virus (HIV) is a retrovirus that infects CD4+ T cell lymphocytes in humans, leading to the development of Acquired Immunodeficiency Syndrome (AIDS) if left untreated. While current treatment methods, including antiretroviral combination treatments, effectively limit HIV replication, HIV can evade these treatments due to its high mutation rate. Long-term antiretroviral treatment can also be toxic to patients, meaning patients would benefit from a new mechanism of HIV treatment. RNA interference (RNAi) is an antiviral pathway found in mammals, plants, and insects that involves a small-interfering RNA that is incorporated into a protein complex called the RNA-induced Silencing Complex …
Modeling The Role Of Land Conversion On The Spread Of An Epizootic Disease, Dustin Padilla
Modeling The Role Of Land Conversion On The Spread Of An Epizootic Disease, Dustin Padilla
Annual Symposium on Biomathematics and Ecology Education and Research
No abstract provided.
How Environmental Change Will Impact Mosquito-Borne Diseases, Arsal Khan
How Environmental Change Will Impact Mosquito-Borne Diseases, Arsal Khan
Master's Projects and Capstones
Mosquitos, the most lethal species throughout human history, are the most prevalent source of vector-borne diseases and therefore a major global health burden. Mosquito-borne disease incidence is expected to shift with environmental change. These changes can be predicted using species distribution models. With the wide variety of methods used for models, consensus for improving accuracy and comparability is needed. A comparative analysis of three recent modeling approaches revealed that integrating modeling techniques compensates for trade-offs associated with a singular approach. An area that represents a critical gap in our ability to predict mosquito behavior in response to changing climate factors, …
Epidemiological Assessment Of Wolbachia-Based Biocontrol For Reduction Of Dengue Morbidity, Olga Vasilieva, Oscar E. Escobar, Hector J. Martinez, Pierre-Alexandre Bliman, Yves Dumont
Epidemiological Assessment Of Wolbachia-Based Biocontrol For Reduction Of Dengue Morbidity, Olga Vasilieva, Oscar E. Escobar, Hector J. Martinez, Pierre-Alexandre Bliman, Yves Dumont
Biology and Medicine Through Mathematics Conference
No abstract provided.
Mechanisms And Mitigation: Effects Of Light Pollution On West Nile Virus Dynamics, Meredith E. Kernbach
Mechanisms And Mitigation: Effects Of Light Pollution On West Nile Virus Dynamics, Meredith E. Kernbach
USF Tampa Graduate Theses and Dissertations
Light pollution, or the presence of unnatural light at night, is a pervasive and growing problem across the globe. While often pictured in urban centers, light pollution is far reaching and can affect seemingly safe and minimally developed environments. For example, agricultural communities with artificial lighting near facilities can generate such light pollution in rural areas. Further, streetlights and illuminated billboards along roads and highways can generate light pollution far from cities. Given how pervasive this anthropogenic stressor is, it is surprising that not much is known about how artificial light at night, or ALAN, affects humans or wildlife, especially …
Association Between Asymptomatic Malaria Infection And Pregnancy Outcome In Delta State, Nigeria, Sadiatu Sally Obi
Association Between Asymptomatic Malaria Infection And Pregnancy Outcome In Delta State, Nigeria, Sadiatu Sally Obi
Walden Dissertations and Doctoral Studies
Pregnant women are vulnerable due to the pregnancy-induced suppressed immunity in malaria-endemic areas. Asymptomatic malaria in pregnancy (MiP) threatens both the mother, fetus, and neonate via chronic placental malaria which impacts maternal-neonatal exchange. Some studies reported that MiP risk factors vary across locations, however, there are few studies on MiP and pregnancy outcome in Nigeria. The purpose of this study was to investigate the association between asymptomatic placental malaria infection and pregnancy outcome among parturients in Asaba, Delta State, Nigeria. This study was developed with a quantitative methodology that utilized primary and secondary healthcare data from 483 subjects aged 18–49 …
Use Of Lymesim 2.0 To Assess The Potential For Single And Integrated Management Methods To Control Blacklegged Ticks (Ixodes Scapularis; Acari: Ixodidae) And Transmission Of Lyme Disease Spirochetes, Shravani Chitineni, Elizabeth R. Gleim, Holly D. Gaff
Use Of Lymesim 2.0 To Assess The Potential For Single And Integrated Management Methods To Control Blacklegged Ticks (Ixodes Scapularis; Acari: Ixodidae) And Transmission Of Lyme Disease Spirochetes, Shravani Chitineni, Elizabeth R. Gleim, Holly D. Gaff
Undergraduate Honors Theses
Annual Lyme disease cases continue to rise in the U.S. making it the most reported vector-borne illness in the country. The pathogen (Borrelia burgdorferi) and primary vector (Ixodes scapularis; blacklegged tick) dynamics of Lyme disease are complicated by the multitude of vertebrate hosts and varying environmental factors, making models an ideal tool for exploring disease dynamics in a time- and cost-effective way. In the current study, LYMESIM 2.0, a mechanistic model, was used to explore the effectiveness of three commonly used tick control methods: habitat-targeted acaricide (spraying), rodent-targeted acaricide (bait boxes), and white-tailed deer targeted acaricide (4-poster …
Prevalence Of Rats And Rodent Borne Pathogens Across Post-Katrina New Orleans, Bruno Marco Ghersi
Prevalence Of Rats And Rodent Borne Pathogens Across Post-Katrina New Orleans, Bruno Marco Ghersi
Doctoral Dissertations
Disasters are happening at an increasingly higher rate and intensity a trend that is expected to continue as more humans migrate to coastal urban areas. Disasters, and as importantly, disaster recovery can affect how native and pest populations will recover. My aim was to improve understanding of disease risk by evaluating the socioecological conditions that have shaped commensal rat recovery and distribution, as well as the pathogens they carry, across New Orleans after Hurricane Katrina. I first estimated relative abundance and distribution of commensal rats from rodent trapping conducted between mid-2014 and early-2017 across 96 sites in 10 areas of …
Geographic And Intra-Racial Disparities In Early-Onset Colorectal Cancer In The Seer 18 Registries Of The United States, Wesal H. Abualkhair, Meijiao Zhou, Carolina O. Ochoa, Leonel Lacayo, Caitlin Murphy, Xiao Cheng Wu, Jordan J. Karlitz
Geographic And Intra-Racial Disparities In Early-Onset Colorectal Cancer In The Seer 18 Registries Of The United States, Wesal H. Abualkhair, Meijiao Zhou, Carolina O. Ochoa, Leonel Lacayo, Caitlin Murphy, Xiao Cheng Wu, Jordan J. Karlitz
School of Medicine Faculty Publications
Background: Although early-onset colorectal cancer (EOCRC) incidence rates (IRs) are increasing, geographic and intra-racial IR disparities are not well defined. Methods: 2000-2015 Surveillance, Epidemiology, and End Results (SEER) program CRC IR Analysis (170,434 cases) was performed from ages 30 to 60 in four US regions, 18 individual registries, metropolitan and nonmetropolitan locations and stratified by race. Analyses were conducted in 1-year and 5-year age increments. Results: Wide US regional EOCRC IR variations exist: For example, age 45 IRs in the south are 26.8/100,000, 36.0% higher than the West, 19.7/100,000 (p < 0.0001). Disparities magnify between individual registries: EOCRC IRs in highest risk registries were 177-348% (Alaska Natives), 75-200% (Hawaii), 76-128% (Louisiana), and 61-125% (Kentucky) higher than lowest risk registries depending on age. EOCRC IRs are 18.2%-25.6% higher in nonmetropolitan versus metropolitan settings. Wide geographic intra-racial disparities exist. Within the White population, the greatest IR difference (78.8%) was between Kentucky (5.9/100,000) and Los Angeles (3.3/100,000) in 30- to 34-year-olds (p <.0001). Within the Black population, the greatest difference (136.2%) was between rural Georgia (30.7/100,000) and California excluding San Francisco-Oakland/San Jose-Monterey/Los Angeles (13/100,000) in 40- to 44-year-olds (p = 0003). Conclusion: Marked geographic EOCRC disparities exist with disproportionately high IRs in Alaska Natives, Hawaii, and southern registries. Geographic intra-racial disparities are present within White and Black populations. In Blacks, there are disproportionately high EOCRC IRs in rural Georgia. Although vigilance is required in all populations, attention must be paid to these higher risk populations. Potential interventions include assuring early investigation of symptoms, targeting modifiable risk factors and utilizing earlier age 45 screening options supported by some guidelines.
The Role Of Variation In Mate Choice And Wolbachia Infection On Aedes Aegypti Population Dynamics, Bernardo Ameneyro
The Role Of Variation In Mate Choice And Wolbachia Infection On Aedes Aegypti Population Dynamics, Bernardo Ameneyro
Biology and Medicine Through Mathematics Conference
No abstract provided.
On The Inadequacy Of Species Distribution Models For Modelling The Spread Of Sars-Cov-2: Response To Araújo And Naimi, Joseph D. Chipperfield, Blas M. Benito, Robert B. O'Hara, Richard J. Telford, Colin J. Carlson
On The Inadequacy Of Species Distribution Models For Modelling The Spread Of Sars-Cov-2: Response To Araújo And Naimi, Joseph D. Chipperfield, Blas M. Benito, Robert B. O'Hara, Richard J. Telford, Colin J. Carlson
Public Health Resources
The ongoing pandemic of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is causing significant damage to public health and economic livelihoods, and is putting significant strains on healthcare services globally. This unfolding emergency has prompted the preparation and dissemination of the article “Spread of SARS-CoV-2 Coronavirus likely to be constrained by climate” by Araújo and Naimi (2020). The authors present the results of an ensemble forecast made from a suite of species distribution models (SDMs), where they attempt to predict the suitability of the climate for the spread of SARS-CoV-2 over the coming months. They argue that climate is …
A Comparative Spatial And Climate Analysis Of Human Granulocytic Anaplasmosis And Human Babesiosis In New York State (2013-2018), Collin J. O'Connor
A Comparative Spatial And Climate Analysis Of Human Granulocytic Anaplasmosis And Human Babesiosis In New York State (2013-2018), Collin J. O'Connor
Legacy Theses & Dissertations (2009 - 2024)
Human granulocytic anaplasmosis (HGA) and human babesiosis are tick-borne diseases spread by Ixodes scapularis (the blacklegged or deer tick) and are the result of infection with Anaplasma phagocytophilum and Babesia microti, respectively. In New York State (NYS), incidence rates of these diseases increased concordantly until around 2013, when rates of HGA began to increase more rapidly than human babesiosis, and the spatial extent of the diseases diverged. Surveillance data of tick-borne pathogens (2007 to 2018) and reported human cases of HGA (n=4,297) and human babesiosis (n=2,986) (2013 to 2018) from the New York State Department of Health (NYSDOH) showed a …
The Potential For Dickeya Dianthicola To Be Vectored By Two Common Insect Pests Of Potatoes, Jonas K. Insinga
The Potential For Dickeya Dianthicola To Be Vectored By Two Common Insect Pests Of Potatoes, Jonas K. Insinga
Electronic Theses and Dissertations
Dickeya dianthicola (Samson) causing blackleg and soft rot was first detected in potatoes grown in Maine in 2014. Previous work has suggested that insects, particularly aphids, may be able to vector bacteria in this genus between plants, but no conclusive work has been done to confirm this theory. In order to determine whether insect-mediated transmission is likely to occur in potato fields, two model potato pests common in Maine were used: the Colorado potato beetle (Leptinotarsa decimlineata Say) and the green peach aphids (Myzus persicae Sulzer). Olfactometry and recruitment experiments evaluated if either insect discriminates between infected and …
Using Empirical And Theoretical Approaches To Control Outbreaks Of An Emerging Disease (Swimmer’S Itch) In The Midwest Of The U.S.A., Gregory J. Sandland, James Peirce
Using Empirical And Theoretical Approaches To Control Outbreaks Of An Emerging Disease (Swimmer’S Itch) In The Midwest Of The U.S.A., Gregory J. Sandland, James Peirce
Annual Symposium on Biomathematics and Ecology Education and Research
No abstract provided.
Characterizing The Permanence And Stationary Distribution For A Family Of Malaria Stochastic Models, Divine Wanduku
Characterizing The Permanence And Stationary Distribution For A Family Of Malaria Stochastic Models, Divine Wanduku
Biology and Medicine Through Mathematics Conference
No abstract provided.
A Review Of Rat Lungworm Infection And Recent Data On Its Definitive Hosts In Hawaii, Chris N. Niebuhr, Susan I. Jarvi, Shane R. Siers
A Review Of Rat Lungworm Infection And Recent Data On Its Definitive Hosts In Hawaii, Chris N. Niebuhr, Susan I. Jarvi, Shane R. Siers
Human–Wildlife Interactions
Rat lungworm (Angiostrongylus cantonensis) is a zoonotic nematode that causes rat lungworm disease (angiostrongyliasis), a potentially debilitating form of meningitis, in humans worldwide. The definitive hosts for rat lungworm are primarily members of the genus Rattus, with gastropods as intermediate hosts. This parasite has emerged as an important public health concern in the United States, especially in Hawaii, where the number of human cases has increased in the last decade. Here we discuss the current knowledge of the rat lungworm, including information on the life cycle and host species, as well as updates on known infection levels. Three …
The Role Of Outcome Preferences In Optimizing Heterogenous Disease Control Strategies., Evan Milliken
The Role Of Outcome Preferences In Optimizing Heterogenous Disease Control Strategies., Evan Milliken
Biology and Medicine Through Mathematics Conference
No abstract provided.
Spatial Modelling And Wildlife Health Surveillance: A Case Study Of White Nose Syndrome In Ontario, Lauren Yee
Spatial Modelling And Wildlife Health Surveillance: A Case Study Of White Nose Syndrome In Ontario, Lauren Yee
Theses and Dissertations (Comprehensive)
Wildlife data is often limited by survey effort, small sample sizes, and spatial biases associated with collection and missing data. These factors can create unique challenges from a surveillance perspective when trying to extract spatial patterns of habitat suitability and disease distributions for conservation and management purposes. This thesis examined data quality from a wildlife health database in the context of spatial analysis of wildlife disease. Spatial analysis of the data to predict habitat suitability of bats and white nose syndrome afflicted bats was examined by using the MaxEnt modelling method. Methods to reduce spatial bias were examined and specific …
A Stochastic Epidemiological Model Of The Response Of American Chestnut Populations To Fungal Blight, Kelsey Lieberman, Rebecca Rouleau, Anita Davelos Baines, Martin Allen
A Stochastic Epidemiological Model Of The Response Of American Chestnut Populations To Fungal Blight, Kelsey Lieberman, Rebecca Rouleau, Anita Davelos Baines, Martin Allen
Annual Symposium on Biomathematics and Ecology Education and Research
No abstract provided.
The Influence Of Temperature Variation On Dengue Fever: A Model-Based Investigation, Michael A. Robert, Paula D. Weber, Rebecca C. Christofferson, Christopher N. Mores, Helen J. Wearing
The Influence Of Temperature Variation On Dengue Fever: A Model-Based Investigation, Michael A. Robert, Paula D. Weber, Rebecca C. Christofferson, Christopher N. Mores, Helen J. Wearing
Biology and Medicine Through Mathematics Conference
No abstract provided.
Dynamics Of Two Pathogens In A Single Tick Population, Alexis White
Dynamics Of Two Pathogens In A Single Tick Population, Alexis White
Biology and Medicine Through Mathematics Conference
No abstract provided.
Fighting Microbial Drug Resistance: A Primer On The Role Of Evolutionary Biology In Public Health, Gabriel Perron, R. Inglis, Pleuni Pennings, Sarah Cobey
Fighting Microbial Drug Resistance: A Primer On The Role Of Evolutionary Biology In Public Health, Gabriel Perron, R. Inglis, Pleuni Pennings, Sarah Cobey
Biology Department Faculty Works
Although microbes have been evolving resistance to antimicrobials for millennia, the spread of resistance in pathogen populations calls for the development of new drugs and treatment strategies. We propose that successful, long-term resistance management requires a better understanding of how resistance evolves in the first place. This is an opportunity for evolutionary biologists to engage in public health, a collaboration that has substantial precedent. Resistance evolution has been an important tool for developing and testing evolutionary theory, especially theory related to the genetic basis of new traits and constraints on adaptation. The present era is no exception. The articles in …
The Relationship Of Female Physical Attractiveness To Body Fatness, Guanlin Wang, Kurosh Djafarian, Chima A. Egedigwe, Asmaa El Hamdouchi, Robert Ojiambo, Harris Ramuth, Sandra Johanna Wallner-Liebmann, Sonja Lackner, Adama Diouf, Justina Sauciuvenaite, Catherine Hambly, Lobke M. Vaanholt, Mark D. Faries, John R. Speakman
The Relationship Of Female Physical Attractiveness To Body Fatness, Guanlin Wang, Kurosh Djafarian, Chima A. Egedigwe, Asmaa El Hamdouchi, Robert Ojiambo, Harris Ramuth, Sandra Johanna Wallner-Liebmann, Sonja Lackner, Adama Diouf, Justina Sauciuvenaite, Catherine Hambly, Lobke M. Vaanholt, Mark D. Faries, John R. Speakman
Faculty Publications
Aspects of the female body may be attractive because they signal evolutionary fitness. Greater body fatness might reflect greater potential to survive famines, but individuals carrying larger fat stores may have poor health and lower fertility in non-famine conditions. A mathematical statistical model using epidemiological data linking fatness to fitness traits, predicted a peaked relationship between fatness and attractiveness (maximum at body mass index (BMI) = 22.8 to 24.8 depending on ethnicity and assumptions). Participants from three Caucasian populations (Austria, Lithuania and the UK), three Asian populations (China, Iran and Mauritius) and four African populations (Kenya, Morocco, Nigeria and Senegal) …
Evolution In Action: Climate Change, Biodiversity Dynamics And Emerging Infectious Disease, Eric P. Hoberg, Daniel R. Brooks
Evolution In Action: Climate Change, Biodiversity Dynamics And Emerging Infectious Disease, Eric P. Hoberg, Daniel R. Brooks
Harold W. Manter Laboratory of Parasitology: Faculty and Staff Publications
Climatological variation and ecological perturbation have been pervasive drivers of faunal assembly, structure and diversification for parasites and pathogens through recurrent events of geographical and host colonization at varying spatial and temporal scales of Earth history. Episodic shifts in climate and environmental settings, in conjunction with ecological mechanisms and host switching, are often critical determinants of parasite diversification, a view counter to more than a century of coevolutionary thinking about the nature of complex host–parasite assemblages. Parasites are resource specialists with restricted host ranges, yet shifts onto relatively unrelated hosts are common during phylogenetic diversification of parasite lineages and directly …
Complexity And Uncertainty In Human And Ecological Risk Assessment, Matthew Jordan Dellinger
Complexity And Uncertainty In Human And Ecological Risk Assessment, Matthew Jordan Dellinger
Theses and Dissertations
Multiple interacting stressors in the environment present increasingly complex risks to human health. Too often, however, the data required for traditional risk assessment are either lacking or unavailable at the necessary spatial or temporal scale. In addition, assessment practices and management policies need to move away from single factor approaches in order to accommodate the reality of complex chemical mixtures and environmental stressors. Recent literature suggests that a paradigm shift is under way. This points to a need for the development of new techniques both for rapid data collection and flexible risk assessment strategies that can adapt to make use …
Two Boundaries Separate Borrelia Burgdorferi Populations In North America, Gabriele Margos, Jean I. Tsao, Santiago Castillo-Ramirez, Yvette A. Girard, Anne G. Hoen
Two Boundaries Separate Borrelia Burgdorferi Populations In North America, Gabriele Margos, Jean I. Tsao, Santiago Castillo-Ramirez, Yvette A. Girard, Anne G. Hoen
Dartmouth Scholarship
Understanding the spread of infectious diseases is crucial for implementing effective control measures. For this, it is important to obtain information on the contemporary population structure of a disease agent and to infer the evolutionary processes that may have shaped it. Here, we investigate on a continental scale the population structure of Borrelia burgdorferi, the causative agent of Lyme borreliosis (LB), a tick-borne disease, in North America. We test the hypothesis that the observed d population structure is congruent with recent population expansions and that these were preceded by bottlenecks mostly likely caused by the near extirpation in the 1900s …
Modeling And Analysis Of The Spread Of Japanese Encephalitis With Environmental Effects, Ram Naresh, Surabhi Pandey
Modeling And Analysis Of The Spread Of Japanese Encephalitis With Environmental Effects, Ram Naresh, Surabhi Pandey
Applications and Applied Mathematics: An International Journal (AAM)
A nonlinear mathematical model for the spread of Japanese Encephalitis, caused by infected mosquito feeding on susceptible human population incorporating demographic and environmental factors is proposed and analyzed. In the modeling process, it is assumed that the growth rates of reservoir animal population and vector mosquito population are enhanced due to environmental discharges caused by human population related factors. The model is analyzed by stability theory of differential equations and computer simulation. Both the disease-free and the endemic equilibria are found and their stability is investigated. It is found that whenever the disease-free equilibrium is locally asymptotically stable, the endemic …