China
Africa
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The Parasite's Way of Life
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
4. The R-value, related to the basic reproduction number (R0) but taking into account the immune status of the population, describes the average number of new cases in susceptible individuals derived from one infected individual. If members of the potential host population are immune to the infectious agent in question, they cannot become infected, and this causes R to change as the proportion of individuals that are immune changes. In the following cases would R be expected to rise or fall: If a sudden influx of new potential host individuals who have not previously been exposed to the parasite in question entered the population?If a number of hosts became infected with the parasite, and subsequently became immune to later infections with the same parasite?If a number of potential hosts were vaccinated against this particular parasite?If a number of new babies are born?
Challenges and Innovations in Mathematical Modelling of COVID-19
Published in Srijan Goswami, Chiranjeeb Dey, COVID-19 and SARS-CoV-2, 2022
Swarnali Sharma, Malay Banerjee*
The detailed calculations for the basic reproduction number, the final size of the epidemic, and other relevant epidemic characteristics for the models (2.1) and (2.2) are available in Sharma et al. (2020). The way we have derived the basic reproduction number as well as the effective reproduction number for the model (2.2) can easily be extended for a model of a similar type consisting of more than two groups.
And Now, as Promised
Published in Rae-Ellen W. Kavey, Allison B. Kavey, Viral Pandemics, 2020
Rae-Ellen W. Kavey, Allison B. Kavey
Crucial findings with any new disease include the range of clinical severity, the extent of transmission and rates of infection – all remained unknown at this stage despite more than 71,000 cases of COVID-19 and 1600 deaths, as of February 17, 2020. The virus spreads both directly – through physical transfer between people through close contact with oral or nasal secretions – and indirectly, through contact with droplets deposited on nearby surfaces when an infected person coughs or sneezes, which can then be carried to the eyes, nose or mouth of a healthy subject. We do know that 2019-nCoV/ SARS-CoV-2 is too big to stay suspended in the air for any significant length of time or to travel more than a few feet and this should limit transmission. As with SARS, droplets generated during medical procedures can be aerosolized, augmenting the potential for infection of healthcare providers. Hand hygiene for both infected and uninfected individuals and personal protective barriers – gowns, gloves, masks, and goggles – reduce droplet transmission. Estimates of the basic reproduction number or R0 for the virus – the number of additional persons one case infects over the course of their illness – have generally ranged from 2.2 to 3.6, but there are estimates as high as 6.5.13 (An R0 of less than 1 indicates very low transmission potential; the higher the R0, the greater the potential for sustained transmission. As an example, the R0 for measles is 18!)
Lessons learned from the SARS-CoV-2 pandemic; from nucleic acid nanomedicines, to clinical trials, herd immunity, and the vaccination divide
Published in Expert Opinion on Drug Delivery, 2023
Hiba Hussain, Aishwarya Ganesh, Lara Milane, Mansoor Amiji
R0, or the basic reproduction number is defined as the average number of infections that is produced in a susceptible host population when an infected individual is introduced into that population [90]. The dimensionless metric is calculated taking three factors into account: possibility of infection upon exposure to a contact, contact rate, and duration that an infected individual remains contagious [91]. The value of R0 also characterizes the level of widespread infection due to a pathogen [90]. At the beginning of the pandemic, in Wuhan, the R0 value for SARS-CoV-2 was calculated as 2.2, however with time the R0 value ranged from 1.5 to 6.68 in different countries. The average R0 value was 3.28, which was higher than the estimated 1.4–2.5 range provided by WHO [92]. The higher the R0, the more the vaccine administration is required for herd immunity [92]. On this basis, nations can modify their vaccine distribution plans to efficiently reach herd immunity as the pandemic progresses.
Estimation of the doubling time and reproduction number for COVID-19
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Shamim Ahmed, Mohammad Shemanto, Hasin Azhari, Golam Zakaria
The basic reproduction number or the reproduction number (R0) specifies the average number of the secondary infections caused by one infected individual during the entire infectious period at the start of an outbreak. The definition describes the state where all individuals are susceptible to infection and no other individuals are infected or immunized (naturally or through vaccination). It is one of the fundamental and most often used metrics for the study of infectious disease dynamics. An outbreak is expected to continue if R0 has a value > 1 and to end if R0 is < 1. The first modern application of R0 in epidemiology can be traced by the work of Macdonald (1952). Although MacDonald used Z0 to represent the metric and he called it basic reproduction rate. The use of the word rate suggests a quantity having a unit with a per-time dimension. If R0 were a rate involving time, the metric would provide information about how quickly an epidemic will spread through a population. But R0 does not indicate whether new cases will occur within a specific period of time. That is why calling R0 a rate rather than a number creates confusion. Throughout this paper, we refer this parameter reproduction number.
Fractional dynamics and stability analysis of COVID-19 pandemic model under the harmonic mean type incidence rate
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Amir Khan, Rahat Zarin, Saddam Khan, Anwar Saeed, Taza Gul, Usa Wannasingha Humphries
Keeping the above discussion in mind we formulated a covid 19 epidemic model and analyzed its different dynamics by considering the deterministic approach as well as fractional approach. The basic reproduction number is the threshold value that gives us information whether the disease spreads or not, as has been found by Next Generation Method. Covid 19 models under harmonic mean incidence rate have not given too much attention. Therefore we considered the harmonic mean type incidence rate and in the deterministic model, we established the local as well as the global stability for the said model. To minimize the infected people and maximize the susceptible people one can use optimal control theory by choosing suitable optimal control variables. For this, we used sensitivity analysis to highlight the most highly sensitive parameters which are useful in optimal control theory.