Heterogeneity in epidemic models and its effect on the spread of infection

1998 ◽  
Vol 35 (03) ◽  
pp. 651-661 ◽  
Author(s):  
Håkan Andersson ◽  
Tom Britton
Keyword(s):  
Heterogeneous Population ◽  
Epidemic Models ◽  
Homogeneous Population ◽  
Epidemic Size ◽  
Infection Pressure ◽  
Group A ◽  
Final Epidemic Size ◽  
Spread Of Infection ◽  
Very High ◽  
High Infectivity

We first study an epidemic amongst a population consisting of individuals with the same infectivity but with varying susceptibilities to the disease. The asymptotic final epidemic size is compared with the corresponding size for a homogeneous population. Then we group a heterogeneous population into households, assuming very high infectivity within households, and investigate how the global infection pressure is affected by rearranging individuals between the households. In both situations considered, it turns out that whether or not homogenizing the individuals or households will result in an increased spread of infection actually depends on the infectiousness of the disease.

Heterogeneity in epidemic models and its effect on the spread of infection

1998 ◽  
Vol 35 (3) ◽  
pp. 651-661 ◽  
Author(s):  
Håkan Andersson ◽  
Tom Britton
Keyword(s):  
Heterogeneous Population ◽  
Epidemic Models ◽  
Homogeneous Population ◽  
Epidemic Size ◽  
Infection Pressure ◽  
Group A ◽  
Final Epidemic Size ◽  
Spread Of Infection ◽  
Very High ◽  
High Infectivity

We first study an epidemic amongst a population consisting of individuals with the same infectivity but with varying susceptibilities to the disease. The asymptotic final epidemic size is compared with the corresponding size for a homogeneous population. Then we group a heterogeneous population into households, assuming very high infectivity within households, and investigate how the global infection pressure is affected by rearranging individuals between the households. In both situations considered, it turns out that whether or not homogenizing the individuals or households will result in an increased spread of infection actually depends on the infectiousness of the disease.

scholarly journals Asymptomatic individuals can increase the final epidemic size under adaptive human behavior

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Baltazar Espinoza ◽  
Madhav Marathe ◽  
Samarth Swarup ◽  
Mugdha Thakur
Keyword(s):  
Planning Horizon ◽  
Infection Risk ◽  
Epidemiological Models ◽  
Epidemic Size ◽  
Behavioral Adaptations ◽  
Future State ◽  
Final Epidemic Size ◽  
Asymptomatic Individuals ◽  
The Impact ◽  
Finite Planning Horizon

AbstractInfections produced by non-symptomatic (pre-symptomatic and asymptomatic) individuals have been identified as major drivers of COVID-19 transmission. Non-symptomatic individuals, unaware of the infection risk they pose to others, may perceive themselves—and be perceived by others—as not presenting a risk of infection. Yet, many epidemiological models currently in use do not include a behavioral component, and do not address the potential consequences of risk misperception. To study the impact of behavioral adaptations to the perceived infection risk, we use a mathematical model that incorporates the behavioral decisions of individuals, based on a projection of the system’s future state over a finite planning horizon. We found that individuals’ risk misperception in the presence of non-symptomatic individuals may increase or reduce the final epidemic size. Moreover, under behavioral response the impact of non-symptomatic infections is modulated by symptomatic individuals’ behavior. Finally, we found that there is an optimal planning horizon that minimizes the final epidemic size.

scholarly journals Survey of Human Group C Rotaviruses in Japan during the Winter of 1992 to 1993

1998 ◽  
Vol 36 (1) ◽  
pp. 6-10 ◽  
Author(s):  
Mitsutaka Kuzuya ◽  
Ritsushi Fujii ◽  
Masako Hamano ◽  
Masao Yamada ◽  
Kuniko Shinozaki ◽  
...  
Keyword(s):  
Large Scale ◽  
Blot Hybridization ◽  
Human Group ◽  
Dot Blot ◽  
Passive Hemagglutination ◽  
Group A Rotaviruses ◽  
Group A ◽  
Outer Capsid ◽  
Very High ◽  
Vp7 Gene

Fecal specimens from patients with acute diarrhea were collected from 10 prefectures in Japan over a 6-month period (November 1992 to April 1993), and the specimens that were negative for human group A rotaviruses were screened for the presence of human group C rotaviruses (CHRVs) by the reverse passive hemagglutination test. Of 784 specimens examined, 53 samples (6.8%) that were collected in 7 of 10 prefectures were positive for CHRV, indicating that CHRVs are widely distributed across Japan. Most of the CHRV isolates were detected in March and April, and CHRVs mainly prevailed in children ages 3 to 8 years. The genome electropherotypes of eight strains isolated in five individual prefectures were surprisingly similar to each other and were different from those of CHRV strains isolated to date. The outer capsid glycoprotein (VP7) gene homologies of the isolates retrieved in 1993 were subsequently analyzed by the dot blot hybridization method. As a result, the VP7 genes of the isolates revealed very high levels of homology not only with each other but also with the VP7 gene of the OK118 strain isolated in 1988. These results suggest that a large-scale outbreak of CHRV occurred during the winter of 1992 and 1993 in Japan.

An Outbreak of Fatal Nosocomial Infections Due to Group A Streptococcus on a Medical Ward

1996 ◽  
Vol 17 (7) ◽  
pp. 429-431 ◽  
Author(s):  
L. Ramage ◽  
K. Green ◽  
D. Pyskir ◽  
A.E. Simor
Keyword(s):  
Nosocomial Infections ◽  
Community Hospital ◽  
Group A Streptococcus ◽  
Hospital Setting ◽  
Streptococcal Infections ◽  
Severe Group ◽  
Life Threatening ◽  
Group A ◽  
Spread Of Infection ◽  
Dna Profiles

AbstractGroup A streptococcus is an uncommon but important cause of nosocomial infections. Outbreaks of infection most often have occurred in surgical or obstetrical patients. We describe an outbreak of severe group A streptococcal infections that occurred on a medical unit of a community hospital. Within an 8-day period, three patients developed fatal nosocomial skin and soft-tissue infection due to group A streptococcus. Three nurses who had provided care to one or more of these patients subsequently developed strepto-coccal pharyngitis, and three other nurses were treated with antibiotics for pharyngitis (cultures not obtained). Patient isolates were serotype M-nontypeable, T-11, opacity factor-positive, and shared identical DNA profiles when typed by pulsed-field gel electrophoresis; staff isolates were not available for typing. To prevent further spread of infection, the ward was closed to new admissions, and symptomatic staff were treated with antibiotics and relieved of patient-care duties. This outbreak demonstrates the ability of group A streptococcus to spread rapidly in a hospital setting and to cause severe life-threatening disease in hospitalized patients.

scholarly journals Antiviral treatment for the control of pandemic influenza: some logistical constraints

2007 ◽  
Vol 5 (22) ◽  
pp. 545-553 ◽  
Author(s):  
N Arinaminpathy ◽  
A.R McLean
Keyword(s):  
Influenza Pandemic ◽  
Antiviral Treatment ◽  
Basic Reproductive Number ◽  
Reproductive Number ◽  
Epidemic Size ◽  
Conservative Policy ◽  
Control Programmes ◽  
Final Epidemic Size ◽  
Number Of Treatment ◽  
Modelling Approach

Disease control programmes for an influenza pandemic will rely initially on the deployment of antiviral drugs such as Tamiflu, until a vaccine becomes available. However, such control programmes may be severely hampered by logistical constraints such as a finite stockpile of drugs and a limit on the distribution rate. We study the effects of such constraints using a compartmental modelling approach. We find that the most aggressive possible antiviral programme minimizes the final epidemic size, even if this should lead to premature stockpile run-out. Moreover, if the basic reproductive number R 0 is not too high, such a policy can avoid run-out altogether. However, where run-out would occur, such benefits must be weighed against the possibility of a higher epidemic peak than if a more conservative policy were followed. Where there is a maximum number of treatment courses that can be dispensed per day, reflecting a manpower limit on antiviral distribution, our results suggest that such a constraint is unlikely to have a significant impact (i.e. increasing the final epidemic size by more than 10%), as long as drug courses sufficient to treat at least 6% of the population can be dispensed per day.

EXACT ANALYTICAL EXPRESSIONS FOR THE FINAL EPIDEMIC SIZE OF AN SIR MODEL ON SMALL NETWORKS

2016 ◽  
Vol 57 (4) ◽  
pp. 429-444 ◽  
Author(s):  
K. MCCULLOCH ◽  
M. G. ROBERTS ◽  
C. R. LAING
Keyword(s):  
Initial Conditions ◽  
Transmission Rate ◽  
Sir Model ◽  
Contact Network ◽  
Sir Epidemic Model ◽  
Node Number ◽  
Sir Epidemic ◽  
Epidemic Size ◽  
Final Epidemic Size ◽  
Analytical Expressions

We investigate the dynamics of a susceptible infected recovered (SIR) epidemic model on small networks with different topologies, as a stepping stone to determining how the structure of a contact network impacts the transmission of infection through a population. For an SIR model on a network of$N$nodes, there are$3^{N}$configurations that the network can be in. To simplify the analysis, we group the states together based on the number of nodes in each infection state and the symmetries of the network. We derive analytical expressions for the final epidemic size of an SIR model on small networks composed of three or four nodes with different topological structures. Differential equations which describe the transition of the network between states are also derived and solved numerically to confirm our analysis. A stochastic SIR model is numerically simulated on each of the small networks with the same initial conditions and infection parameters to confirm our results independently. We show that the structure of the network, degree of the initial infectious node, number of initial infectious nodes and the transmission rate all significantly impact the final epidemic size of an SIR model on small networks.

A New Single-Crystal Adsorption Calorimeter for Determining Metal Adsorption and Adhesion Energies

1996 ◽  
Vol 440 ◽  
Author(s):  
J. T. Stuckless ◽  
D. Starr ◽  
D. Bald ◽  
Charles T. Campbell
Keyword(s):  
Single Crystal ◽  
Thermal Contact ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Crystalline Oxide ◽  
Group A ◽  
Adsorption Heats ◽  
Very High ◽  
Detailed Function ◽  
Oxide Adhesion

AbstractA microcalorimeter for measuring adsorption heats on clean single-crystal surfaces is described. The principle is similar to that pioneered by David King's group: A pulse of gas from a molecular beam adsorbs on an ultrathin single crystal's surface, causing a measurable transient heat input and temperature rise. Our novel heat detector is a 9 μm pyroelectric polymer ribbon, which is mechanically driven to make a gentle mechanical/thermal contact to the back of the singlecrystal sample during measurements. Advantages include use of thicker samples (>3 microns), sample preparation at very high temperatures, and measurements at 100 K. We have applied this to study the heats of adsorption of metals on clean, well-defined and single-crystalline oxide surfaces as a detailed function of coverage, from which we also extract the metal/oxide adhesion energy. We obtain pulse-to-pulse standard deviations of >2% for pulses containing >0.03 ML of Cu, and absolute accuracy within a few percent.

scholarly journals Improving early epidemiological assessment of emerging Aedes-transmitted epidemics using historical data

2018 ◽  
Author(s):  
Julien Riou ◽  
Chiara Poletto ◽  
Pierre-Yves Boëlle
Keyword(s):  
Historical Data ◽  
A Priori ◽  
Total Duration ◽  
Reproduction Ratio ◽  
Peak Incidence ◽  
Incidence Data ◽  
Epidemic Size ◽  
Data Points ◽  
Final Epidemic Size ◽  
Reporting Rates

AbstractModel-based epidemiological assessment is useful to support decision-making at the beginning of an emerging Aedes-transmitted outbreak. However, early forecasts are generally unreliable as little information is available in the first few incidence data points. Here, we show how past Aedes-transmitted epidemics help improve these predictions. The approach was applied to the 2015-2017 Zika virus epidemics in three islands of the French West Indies, with historical data including other Aedes-transmitted diseases (Chikungunya and Zika) in the same and other locations. Hierarchical models were used to build informative a priori distributions on the reproduction ratio and the reporting rates. The accuracy and sharpness of forecasts improved substantially when these a priori distributions were used in models for prediction. For example, early forecasts of final epidemic size obtained without historical information were 3.3 times too high on average (range: 0.2 to 5.8) with respect to the eventual size, but were far closer (1.1 times the real value on average, range: 0.4 to 1.5) using information on past CHIKV epidemics in the same places. Likewise, the 97.5% upper bound for maximal incidence was 15.3 times (range: 2.0 to 63.1) the actual peak incidence, and became much sharper at 2.4 times (range: 1.3 to 3.9) the actual peak incidence with informative a priori distributions. Improvements were more limited for the date of peak incidence and the total duration of the epidemic. The framework can adapt to all forecasting models at the early stages of emerging Aedes-transmitted outbreaks.

scholarly journals Infecção relacionada a assistência à saúde: uma revisão da literatura

2015 ◽  
pp. 50
Author(s):  
Zildo Alves da Silva ◽  
Luiz Faustino dos Santos Maia ◽  
Iris Maria de Pádua ◽  
Janaina Esser Inácio ◽  
Thaís Macedo Pio
Keyword(s):  
Health Care ◽  
High Risk ◽  
Continuing Education ◽  
Health Professionals ◽  
Care Service ◽  
Health Care Service ◽  
Cross Infection ◽  
Patient Health ◽  
Spread Of Infection ◽  
Very High

Este artigo tem por objetivo descrever as intervenções do enfermeiro na prevenção para diminuir as infecções relacionadas com a assistência à saúde por meio de uma revisão da literatura. As infecções tendem a ser um risco muito alto a saúde dos usuários, pois acarreta um maior tempo de tratamento, e possíveis complicações a saúde dos pacientes. A disseminação de infecções em ambiente hospitalar e na assistência do serviço de saúde, com frequência e proveniente da infecção cruzada, é a via de contaminação mais comum ocorre entre as mãos. A educação permanente entre profissionais de saúde, pacientes, familiares e visitantes, é de extrema necessidade para contribuir no controle de infecção.Descritores: Enfermagem, Infecção, Assistência. Infection related to health care: a literature reviewAbstract: This article aims to describe the interventions of nurses in prevention to reduce infections related to health care through a literature review. Infections tend to be a very high risk the health of users since it involves a longer time of treatment, possible complications and patient health. The spread of infection in hospitals and health care service often and from the cross-infection is the most common route of infection is in his hands. The continuing education of health professionals, patients, families and visitors is of extreme necessity to contribute to the control of infection. Descriptors: Nursing, Infection, Assistance. Infección relacionada con la atención de salud: una revisión de la literaturaResumen: Este artículo tiene como objetivo describir las intervenciones de las enfermeras en la prevención para reducir las infecciones relacionadas con la atención de la salud a través de una revisión de la literatura. Las infecciones tienden a ser un muy alto riesgo la salud de los usuarios, ya que implica un tratamiento más largo, y las posibles complicaciones de la salud de los pacientes. La propagación de la infección en los hospitales y servicios de salud a menudo y de la infección cruzada es la vía más común de infección está en sus manos. La formación continuada de los profesionales de salud, los pacientes, las familias y los visitantes es de extrema necesidad de contribuir al control de la infección. Descriptores: Enfermería, Infección, Asistencia.

scholarly journals Assessing the impact of adherence to Non-pharmaceutical interventions and indirect transmission on the dynamics of COVID-19: a mathematical modelling study

2021 ◽  
Author(s):  
Sarafa A. Iyaniwura ◽  
Musa Rabiu ◽  
Jummy F. David ◽  
Jude D. Kong
Keyword(s):  
Public Health ◽  
Reproduction Number ◽  
Health Policies ◽  
Public Health Policies ◽  
Indirect Transmission ◽  
Epidemic Size ◽  
Final Epidemic Size ◽  
The Impact ◽  
Size Relation ◽  
Pharmaceutical Interventions

AbstractAdherence to public health policies such as the non-pharmaceutical interventions implemented against COVID-19 plays a major role in reducing infections and controlling the spread of the diseases. In addition, understanding the transmission dynamics of the disease is also important in order to make and implement efficient public health policies. In this paper, we developed an SEIR-type compartmental model to assess the impact of adherence to COVID-19 non-pharmaceutical interventions and indirect transmission on the dynamics of the disease. Our model considers both direct and indirect transmission routes and stratifies the population into two groups: those that adhere to COVID-19 non-pharmaceutical interventions (NPIs) and those that do not adhere to the NPIs. We compute the control reproduction number and the final epidemic size relation for our model and study the effect of different parameters of the model on these quantities. Our results show that direct transmission has more effect on the reproduction number and final epidemic size, relative to indirect transmission. In addition, we showed that there is a significant benefit in adhering to the COVID-19 NPIs.

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