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Fundamental Epidemiology
Published in Frank R. Spellman, Fundamentals of Wastewater-Based Epidemiology, 2021
Carrier. A person or animal without apparent disease that harbors a specific infectious agent and is capable of transmitting the agent to others. The carrier state may occur in an individual with an infection that is not apparent throughout its course (known as asymptomatic carrier), or during the incubation period, convalescence, and post convalescence of an individual with a clinically recognizable disease. The carrier state may be of short or long duration (transient carrier or chronic carrier).
A Study on Mathematical and Computational Models in the Context of COVID-19
Published in Chhabi Rani Panigrahi, Bibudhendu Pati, Mamata Rath, Rajkumar Buyya, Computational Modeling and Data Analysis in COVID-19 Research, 2021
Understanding the modeling of SEIAR is more important than previous models, as the asymptomatic population plays a critical role in the spread of COVID-19. Individuals who are asymptomatic cause huge damage to the process of controlling the pandemic. We understand that the individuals who do not experience symptoms but are positive in serological tests or blood tests are identified as asymptomatic carriers. The SEIAR model was used to elucidate the transmission dynamics of the swine flu outbreak in 2009 (Adekola et al., 2020). The total population N is divided into five segments: susceptible, exposed, infectious, asymptomatic, and recovered; N = S(t) + E(t) + I(t) + A(t) + R(t). Initially, the total population is susceptible. β is the transmission rate from susceptible to other states. α is mean recovery rate. Other fractions (1−p) proceed to the asymptomatic state during the same time (k), with asymptomatic persons having much less ability to transmit the infection. Let q be the factor which decides the transmissibility in asymptomatic individuals, so 0 < q < 1.The differential equations that describe this are: dsdt=−βS1+qAdEdt=βS1+qA−kEdIdt=pkE−αIdAdt=1−pkE−nAdRdt=αI+nAdCdt=αI
Analysis of an SVIC model with age-dependent infection and asymptomatic carriers
Published in Applicable Analysis, 2018
Jinliang Wang, Di Wu, Hongquan Sun
Mathematical modeling of HBV infection that incorporating vaccination and age as important factors have been used to understand transmission dynamics of HBV and providing suggestions for clinical treatment by some researchers; see Edmunds et al. [4], McLean and Blumberg [5], Zhao, Xu, and Lu [6], etc. Its quantitative analysis may describe the influence of the heterogeneity in infectious individuals on transmission dynamics of HBV infection. Acute HBV infection causes chronic (long-term) infection (long-term asymptomatic carriers) in 30–90 of persons infected as infants or young children and in less than 5 of adolescents and adults (Shepard et al. [7], Goldstein et al. [8]). Asymptomatic carriers are able to transmit their illness but do not exhibit any symptoms. These are chronic HBV carriers.