scholarly journals Is the increased transmissibility of SARS-CoV-2 variants driven by within or outside-host processes?

2021 ◽  
Author(s):  
Yehuda Arav ◽  
Eyal Fattal ◽  
Ziv Klausner
Keyword(s):  
Mathematical Model ◽  
Infected Individual ◽  
Viral Transmission ◽  
Susceptible Individual ◽  
Behavioral Measures ◽  
Viral Shedding ◽  
Virus Transfer

Understanding the factors that increase the transmissibility of the recently emerging variants of SARS-CoV-2 can aid in mitigating the COVID-19 pandemic. The enhanced transmissibility could be attributed to enhanced within-host processes, such as contagiousness (viral shedding by an infected individual) and infectivity (the probability of a susceptible individual to get infected), or outside-host processes, such as viral stability on surfaces and in the air. We utilized a mathematical model in order to theoretically analyze the specific mechanisms of virus transfer between an infected and susceptible individual. This allowed us to examine how the within-host or outside-host processes affect the overall viral transmission. Our analysis is based the available data on the Alpha, Epsilon and Delta variants as well as the currently emerging Omicron variant. We found that the higher transmissibility of the SARS-CoV-2 variants can be attributed only to within-host processes. Specifically, enhanced contagiousness drives the Delta variant transmissibility, while the Alpha, Epsilon and Omicron are characterized by an enhanced infectivity. Since outside-host processes have little contribution to the observed increase in the transmissibility, leading stricter hygienic and behavioral measures than those that were already applied are not expected to achieve a pronounced mitigating effect.

scholarly journals A Mathematical Model of Contact Tracing during the 2014–2016 West African Ebola Outbreak

Mathematics ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 608
Author(s):  
Danielle Burton ◽  
Suzanne Lenhart ◽  
Christina J. Edholm ◽  
Benjamin Levy ◽  
Michael L. Washington ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Disease Management ◽  
Ebola Virus ◽  
Virus Disease ◽  
Infected Individual ◽  
Vital Role ◽  
West African ◽  
Contact Tracing ◽  
The Novel ◽  
Using Data

The 2014–2016 West African outbreak of Ebola Virus Disease (EVD) was the largest and most deadly to date. Contact tracing, following up those who may have been infected through contact with an infected individual to prevent secondary spread, plays a vital role in controlling such outbreaks. Our aim in this work was to mechanistically represent the contact tracing process to illustrate potential areas of improvement in managing contact tracing efforts. We also explored the role contact tracing played in eventually ending the outbreak. We present a system of ordinary differential equations to model contact tracing in Sierra Leonne during the outbreak. Using data on cumulative cases and deaths, we estimate most of the parameters in our model. We include the novel features of counting the total number of people being traced and tying this directly to the number of tracers doing this work. Our work highlights the importance of incorporating changing behavior into one’s model as needed when indicated by the data and reported trends. Our results show that a larger contact tracing program would have reduced the death toll of the outbreak. Counting the total number of people being traced and including changes in behavior in our model led to better understanding of disease management.

scholarly journals 1647. Real-Time Metagenomic Sequencing Reveals Discrete Transmission Clusters Within a Hospital-Associated Norovirus Outbreak

2018 ◽  
Vol 5 (suppl_1) ◽  
pp. S49-S49
Author(s):  
Amanda Casto ◽  
Amanda Adler ◽  
Negar Makhsous ◽  
Xuan Qin ◽  
Kristen Crawford ◽  
...  
Keyword(s):  
Infection Control ◽  
Real Time ◽  
Health Care Systems ◽  
The United States ◽  
Viral Transmission ◽  
Medical System ◽  
Metagenomic Sequencing ◽  
Viral Shedding ◽  
Hospital Units ◽  
Care Systems

Abstract Background Norovirus is the most common cause of acute gastroenteritis in the United States and a major challenge for infection control efforts. The high burden of norovirus in most communities and health care systems makes it difficult to discern viral transmission patterns using traditional epidemiological approaches alone. Methods We performed real-time metagenomic sequencing of norovirus isolates from an outbreak among inpatients at Seattle Children’s Hospital (SCH). We also sequenced isolates from norovirus cases within the larger University of Washington (UW) Medical System that occurred during and after the outbreak. Results Our data showed that the month-long outbreak at SCH was actually characterized by 3 distinct concurrent transmission clusters contained within 3 different hospital units. We were able to report this information to the infection control team at SCH while the outbreak was still in progress. The virus responsible for one of these 3 clusters was genetically stable over a period of 4.5 weeks suggesting serial transmissions from a contaminated fomite, rather than patient to patient transmission. After cases meeting the epidemiological definition for hospital-acquired had ceased, we demonstrated that the virus from one of the 3 outbreak clusters continued to be transmitted to other patients within the SCH medical system. Finally, we showed that one of the patients who acquired norovirus during the outbreak developed a chronic infection with viral shedding documented up until the time of the patient’s death, 8 months after the outbreak. Conclusion These results demonstrate the value of using metagenomics as an adjunct to traditional epidemiologic techniques in the setting of a hospital-associated norovirus outbreak. Real-time metagenomic sequencing elucidated viral transmission patterns within the outbreak while it was still in progress and follow-up sequencing revealed further infections due to an outbreak-associated viral strain even after the outbreak was thought to be over. Given this potential, metagenomic analyses represent an invaluable, largely untapped resource for improving our understanding of and reducing adverse effects from viral outbreaks. Disclosures All authors: No reported disclosures.

scholarly journals Comparison of an Air-Fed Mask System with Hospital-Issued Personal Protection Equipments for Dental Aerosol Protection During the COVID-19 Pandemic

2021 ◽  
Vol 15 (1) ◽  
pp. 742-747
Author(s):  
John B. Bridgman ◽  
Andrew L. Newsom ◽  
David J. Chrisp ◽  
Abi E. Estelle ◽  
Mark Saunders
Keyword(s):  
High Speed ◽  
Infected Individual ◽  
Face Mask ◽  
External Source ◽  
Low Flow ◽  
Test Model ◽  
Viral Shedding ◽  
Dental Instruments ◽  
Test Conditions ◽  
The Face

Aim: A pilot study was conducted with the aim of developing a system to protect the eyes, nose, and mouth from the aerosol generated from a high-speed dental handpiece during the COVID-19 pandemic. Background: The SARS-CoV-2 virus is known to be present in the saliva of an infected individual during the contagious viral shedding phase of the disease. The use of rotary dental instruments places oral health practitioners at risk of contracting COVID-19 from infected individuals. In particular, it is very difficult to protect the mucous membranes of the face against the extremely fine aerosol produced from a high-speed dental handpiece. Objectives: This study aimed to develop and test a novel PPE system for use during the COVID-19 pandemic. An air-fed spray-painting mask was used under a plastic hood to protect against the aerosol from a high-speed dental handpiece. This was found to be superior compared to hospital-issued N-95 masks and eye protection in our test model. Methods: Subjects donned various forms of PPE whilst using a high-speed dental handpiece in a confined cubicle. The efficacy of each form of PPE was evaluated by adding fluorescein to the water coolant supply line of a high-speed dental handpiece before checking for facial contamination with an ophthalmology slit lamp. Results: Under our test conditions, the N-95 mask did not prevent nasal and mouth contaminations, but the combination of an air-fed mask with a sealed hood prevented these contaminations. Although goggles worn tightly did prevent contamination, the air-fed mask system was far more comfortable and did not fog up. Discussion: Under the rigorous test conditions of our model, we found hospital-issued PPE ineffective. We also found the single strategy of using positive airflow into a face mask ineffective, even with extremely high levels of airflow. Complete protection was only achieved reliably by the combination of physically sealing off the face from the surrounding airspace and using the air-fed system to provide an external source of air to breathe. We effectively made the clinical equivalent of a dive bell helmet. The air-fed mask is supplied by a standard dental air compressor and is simple to install for someone familiar with the technical aspects of compressors. The compressor does not rely on a filter and proves effective with cheap and easily accessible disposable items. Conclusion: Under rigorous testing conditions, the developed air-fed mask system with a sealed hood on low flow performed better than hospital-issued PPE against high-speed dental aerosol protection. The developed system protects the operators from the air of the room contaminated with aerosol and brings in safe air from the outside for them to breathe.

scholarly journals Effectiveness of isolation policies in schools: evidence from a mathematical model of influenza and COVID-19

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11211
Author(s):  
Adam A.C. Burns ◽  
Alexander Gutfraind
Keyword(s):  
Mathematical Model ◽  
Attack Rate ◽  
Day School ◽  
School Structure ◽  
Limited Evidence ◽  
School Closures ◽  
Viral Shedding ◽  
Travel Restrictions ◽  
School Week ◽  
Pharmaceutical Interventions

Background Non-pharmaceutical interventions such as social distancing, school closures and travel restrictions are often implemented to control outbreaks of infectious diseases. For influenza in schools, the Center of Disease Control (CDC) recommends that febrile students remain isolated at home until they have been fever-free for at least one day and a related policy is recommended for SARS-CoV-2 (COVID-19). Other authors proposed using a school week of four or fewer days of in-person instruction for all students to reduce transmission. However, there is limited evidence supporting the effectiveness of these interventions. Methods We introduced a mathematical model of school outbreaks that considers both intervention methods. Our model accounts for the school structure and schedule, as well as the time-progression of fever symptoms and viral shedding. The model was validated on outbreaks of seasonal and pandemic influenza and COVID-19 in schools. It was then used to estimate the outbreak curves and the proportion of the population infected (attack rate) under the proposed interventions. Results For influenza, the CDC-recommended one day of post-fever isolation can reduce the attack rate by a median (interquartile range) of 29 (13–59)%. With 2 days of post-fever isolation the attack rate could be reduced by 70 (55–85)%. Alternatively, shortening the school week to 4 and 3 days reduces the attack rate by 73 (64–88)% and 93 (91–97)%, respectively. For COVID-19, application of post-fever isolation policy was found to be less effective and reduced the attack rate by 10 (5–17)% for a 2-day isolation policy and by 14 (5–26)% for 14 days. A 4-day school week would reduce the median attack rate in a COVID-19 outbreak by 57 (52–64)%, while a 3-day school week would reduce it by 81 (79–83)%. In both infections, shortening the school week significantly reduced the duration of outbreaks. Conclusions Shortening the school week could be an important tool for controlling influenza and COVID-19 in schools and similar settings. Additionally, the CDC-recommended post-fever isolation policy for influenza could be enhanced by requiring two days of isolation instead of one.

IN-VIVOMATHEMATICAL STUDY OF CO-INFECTION DYNAMICS OF HIV-1 ANDMYCOBACTERIUM TUBERCULOSIS

2008 ◽  
Vol 16 (03) ◽  
pp. 357-394 ◽  
Author(s):  
GESHAM MAGOMBEDZE ◽  
WINSTON GARIRA ◽  
EDDIE MWENJE
Keyword(s):  
Mathematical Model ◽  
T Cells ◽  
Cd4 T Cells ◽  
Infected Individual ◽  
Treatment Strategies ◽  
Time Interval ◽  
Infection Dynamics ◽  
Potential Reservoir ◽  
Fast Development ◽  
Hiv 1

Human Immunodeficiency Virus type-1 (HIV-1) fuels the pathogenesis of Mycobacterium tuberculosis (Mtb) in humans. We develop a mathematical model in an attempt to understand the immune mechanisms that are involved during the co-infection of Mtb and HIV-1. Our study reveals that infection of an Mtb infected individual with HIV-1 results in fast development of active TB. The mathematical model analysis and simulations show that Mtb infection is linked to HIV infection through macrophages and CD4+ T cells. The study shows that depletion of macrophages and CD4+ T cells by HIV-1 worsens the picture of Mtb infection and in-turn Mtb infection affects the progression of HIV-1 infection since it is also capable of inducing rapid replication of HIV. Our analytical and numerical simulations show that macrophages are a potential reservoir of HIV particles during HIV-1 infection. Co-infection simulations reveal that co-infection exacerbates more the pathogen that caused the first infection. Simulations also show that co-infection disease progression patterns converge to a similar trend after a considerable time interval irrespective of which pathogen first caused infection and the second pathogen that caused co-infection. This work suggests directions for further studies and potential treatment strategies.

scholarly journals Data suggest COVID-19 affected numbers greatly exceeded detected numbers, in four European countries, as per a delayed SEIQR model

2020 ◽  
Author(s):  
Sankalp Tiwari ◽  
C. P. Vyasarayani ◽  
Anindya Chatterjee
Keyword(s):  
Mathematical Model ◽  
Disease Progression ◽  
Continuum Model ◽  
Pareto Distribution ◽  
Infected Individual ◽  
European Countries ◽  
Single Node ◽  
Long Tail ◽  
The Mean ◽  
The Continuum

Abstract People in many countries are now infected with COVID-19. By now, it is clear that the number of people infected is much more than the number of reported cases. To estimate the infected but undetected/unreported cases using a mathematical model, we can use a parameter called the probability of quarantining an infected individual. This parameter exists in the time-delayed SEIQR model (Scientific Reports, article number: 3505). Two limiting cases of a network of such models are used to estimate the undetected population. The first limit corresponds to the network collapsing onto a single node and is referred to as the mean-$\beta$ model. In the second case, the number of nodes in the network is infinite and results in a continuum model, treating the infectivity as statistically distributed. We use a shifted Pareto distribution to model the infectivity. This distribution has a long tail and incorporates the presence of super-spreaders that contribute to the disease progression. While both the models capture the {\em detected} numbers equally well, the predictions of {\em affected} numbers from the continuum model are more realistic. Results suggest that affected people outnumber detected people by one to two orders of magnitude in Spain, UK, Italy, and Germany.

Cytomegalovirus Infection of Breast Milk and Transmission in Infancy

PEDIATRICS ◽  
1983 ◽  
Vol 72 (3) ◽  
pp. 295-299 ◽  
Author(s):  
Meyer Dworsky ◽  
Martha Yow ◽  
Sergio Stagno ◽  
Robert F. Pass ◽  
Charles Alford
Keyword(s):  
Immune Response ◽  
Birth Weight ◽  
Breast Milk ◽  
Cytomegalovirus Infection ◽  
Viral Transmission ◽  
Severe Illness ◽  
Postpartum Women ◽  
Viral Shedding ◽  
Vaginal Secretions ◽  
Chronic Sequelae

Of unselected postpartum women, 39% reactivated cytomegalovirus in breast milk, vaginal secretions, urine, and/or saliva. Consumption of infected breast milk led to infection of 69% of the infants. Although there was some milk secretory immune response to this virus, it prevented neither viral shedding nor viral transmission. All infected infants chronically shed cytomegalovirus. However, no infants have yet demonstrated chronic sequelae. Two preterm infants did develop a significantly acute problem, pneumonitis, which did resolve. The possibility that an unnecessary and perhaps more severe illness might occur in low-birth-weight seronegative infants fed banked human milk from sources other than the mother is disturbing and needs resolution.

Resources Allocation to Suppress the Spread of the Epidemic: A New Model with Consideration of Regional Influence (Preprint)

2021 ◽  
Author(s):  
Gang Yao ◽  
Yong Liu ◽  
Gang Li ◽  
Xiaoxiang Zhang ◽  
Liang Wang
Keyword(s):  
Infectious Disease ◽  
Infected Individual ◽  
Contact Network ◽  
Resources Allocation ◽  
Susceptible Individual ◽  
Allocation Model ◽  
Short Period ◽  
Multiple Regions ◽  
The Cost ◽  
Allocation Methods

BACKGROUND During epidemics, how to allocate resources to suppress the spread of infectious disease is of great significance. Many researches focused on how to suppress the spread of infectious disease in the contact network. However, obtaining the contact network in a short period of time is difficult. OBJECTIVE When resources cannot meet the needs of multiple regions, it is necessary to consider how to allocate resources among multiple regions to limit the spread of the disease without details of the contact network. METHODS It proposed a resources allocation model to measure the cost of different allocation methods by the number of new infected individuals over a period of time. By calculating the probability of a susceptible individual being infected, it estimated the number of new infected individuals. In order to calculate the probability of a susceptible individual being infected by an infected individual in another region, conditional mutual information was introduced to estimate the strength of association relationship between regions. RESULTS Based on the proposed model, it compared the model costs of four different resources allocation methods and found three factors that affect the performance of each method, including the percentage of infected individuals, the resource coverage percentage, and the distribution of infected individuals in each region. CONCLUSIONS No method is better than other methods under any situations. When resources are allocated, the method with the least cost in a short period of time should be adopted according to the current infections, so as to control the epidemic as soon as possible.

PREMIUM CALCULATIONS FOR COMPARTMENTAL MODEL USING DISCRETE ANALOGUES OF CONTINUOUS LOSS DISTRIBUTIONS

2021 ◽  
pp. 38-41
Author(s):  
Mallappa Mallappa ◽  
Talawar A.S ◽  
Rajani P. Agadi
Keyword(s):  
Compartmental Model ◽  
Infected Individual ◽  
Epidemiological Model ◽  
Susceptible Individual ◽  
Loss Distributions ◽  
Discrete Analogues ◽  
Parameter Values ◽  
Continuous Loss

In the present paper we consider some discrete analogues of continuous loss distributions to illustrate their actuarial applications using a simple deterministic epidemiological model. We give numerical illustrations using different parameter values of discrete analogues of continuous loss distributions. We also give level premiums for annuity assuming future premium to be paid by the susceptible individual or future claim to be made by the infected individual follow some discrete analogues of continuous loss distributions.

scholarly journals State space collapse for critical multistage epidemics

2015 ◽  
Vol 47 (03) ◽  
pp. 715-740
Author(s):  
Florian Simatos
Keyword(s):  
State Space ◽  
Epidemic Model ◽  
Infected Individual ◽  
Sir Model ◽  
Critical Regime ◽  
Susceptible Individual ◽  
Diffusion Approximations ◽  
Unusual Form

We study a multistage epidemic model which generalizes the SIR model and where infected individuals go through K ≥ 1 stages of the epidemic before being removed. An infected individual in stage k ∈ {1, …, K} may infect a susceptible individual, who directly goes to stage k of the epidemic; or it may go to the next stage k + 1 of the epidemic. For this model, we identify the critical regime in which we establish diffusion approximations. Surprisingly, the limiting diffusion exhibits an unusual form of state space collapse which we analyze in detail.

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